Lattice and reflexive polytopes¶
This module provides tools for work with lattice and reflexive polytopes. A convex polytope is the convex hull of finitely many points in \(\RR^n\). The dimension \(n\) of a polytope is the smallest \(n\) such that the polytope can be embedded in \(\RR^n\).
A lattice polytope is a polytope whose vertices all have integer coordinates.
If \(L\) is a lattice polytope, the dual polytope of \(L\) is
A reflexive polytope is a lattice polytope, such that its polar is also a lattice polytope, i.e. it is bounded and has vertices with integer coordinates.
This Sage module uses Package for Analyzing Lattice Polytopes (PALP), which is a program written in C by Maximilian Kreuzer and Harald Skarke, which is freely available under the GNU license terms at http://hep.itp.tuwien.ac.at/~kreuzer/CY/. Moreover, PALP is included standard with Sage.
PALP is described in the paper arXiv math.SC/0204356. Its distribution
also contains the application nef.x, which was created by Erwin
Riegler and computes nef-partitions and Hodge data for toric
complete intersections.
ACKNOWLEDGMENT: polytope.py module written by William Stein was used as an example of organizing an interface between an external program and Sage. William Stein also helped Andrey Novoseltsev with debugging and tuning of this module.
Robert Bradshaw helped Andrey Novoseltsev to realize plot3d function.
Note
IMPORTANT: PALP requires some parameters to be determined during
compilation time, i.e., the maximum dimension of polytopes, the
maximum number of points, etc. These limitations may lead to errors
during calls to different functions of these module. Currently, a
ValueError exception will be raised if the output of poly.x
or nef.x is empty or contains the exclamation mark. The error
message will contain the exact command that caused an error, the
description and vertices of the polytope, and the obtained output.
Data obtained from PALP and some other data is cached and most returned values are immutable. In particular, you cannot change the vertices of the polytope or their order after creation of the polytope.
If you are going to work with large sets of data, take a look at
all_* functions in this module. They precompute different data
for sequences of polynomials with a few runs of external programs.
This can significantly affect the time of future computations. You
can also use dump/load, but not all data will be stored (currently
only faces and the number of their internal and boundary points are
stored, in addition to polytope vertices and its polar).
AUTHORS:
Andrey Novoseltsev (2007-01-11): initial version
Andrey Novoseltsev (2007-01-15):
all_*functionsAndrey Novoseltsev (2008-04-01): second version, including:
dual nef-partitions and necessary convex_hull and minkowski_sum
built-in sequences of 2- and 3-dimensional reflexive polytopes
plot3d, skeleton_show
Andrey Novoseltsev (2009-08-26): dropped maximal dimension requirement
Andrey Novoseltsev (2010-12-15): new version of nef-partitions
Andrey Novoseltsev (2013-09-30): switch to PointCollection.
Maximilian Kreuzer and Harald Skarke: authors of PALP (which was also used to obtain the list of 3-dimensional reflexive polytopes)
Erwin Riegler: the author of nef.x
- sage.geometry.lattice_polytope.LatticePolytope(data, compute_vertices=True, n=0, lattice=None)[source]¶
Construct a lattice polytope.
INPUT:
data– points spanning the lattice polytope, specified as one of:a
point collection(this is the preferred input and it is the quickest and the most memory efficient one);an iterable of iterables (for example, a list of vectors) defining the point coordinates;
a file with matrix data, opened for reading, or
a filename of such a file, see
read_palp_point_collection()for the file format;
compute_vertices– boolean (default:True); ifTrue, the convex hull of the given points will be computed for determining vertices. Otherwise, the given points must be vertices.n– integer (default: 0); ifdatais a name of a file, that contains data blocks for several polytopes, then-th block will be usedlattice– the ambient lattice of the polytope. If not given, a suitable lattice will be determined automatically, most likely thetoric lattice\(M\) of the appropriate dimension.
OUTPUT: a
lattice polytopeEXAMPLES:
sage: points = [(1,0,0), (0,1,0), (0,0,1), (-1,0,0), (0,-1,0), (0,0,-1)] sage: p = LatticePolytope(points) sage: p 3-d reflexive polytope in 3-d lattice M sage: p.vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M
>>> from sage.all import * >>> points = [(Integer(1),Integer(0),Integer(0)), (Integer(0),Integer(1),Integer(0)), (Integer(0),Integer(0),Integer(1)), (-Integer(1),Integer(0),Integer(0)), (Integer(0),-Integer(1),Integer(0)), (Integer(0),Integer(0),-Integer(1))] >>> p = LatticePolytope(points) >>> p 3-d reflexive polytope in 3-d lattice M >>> p.vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M
We draw a pretty picture of the polytope in 3-dimensional space:
sage: p.plot3d().show() # needs palp sage.plot
>>> from sage.all import * >>> p.plot3d().show() # needs palp sage.plot
Now we add an extra point, which is in the interior of the polytope…
sage: points.append((0,0,0)) sage: p = LatticePolytope(points) sage: p.nvertices() 6
>>> from sage.all import * >>> points.append((Integer(0),Integer(0),Integer(0))) >>> p = LatticePolytope(points) >>> p.nvertices() 6
You can suppress vertex computation for speed but this can lead to mistakes:
sage: p = LatticePolytope(points, compute_vertices=False) ... sage: p.nvertices() 7
>>> from sage.all import * >>> p = LatticePolytope(points, compute_vertices=False) ... >>> p.nvertices() 7
Given points must be in the lattice:
sage: LatticePolytope([[1/2], [3/2]]) Traceback (most recent call last): ... ValueError: points [[1/2], [3/2]] are not in 1-d lattice M!
>>> from sage.all import * >>> LatticePolytope([[Integer(1)/Integer(2)], [Integer(3)/Integer(2)]]) Traceback (most recent call last): ... ValueError: points [[1/2], [3/2]] are not in 1-d lattice M!
But it is OK to create polytopes of non-maximal dimension:
sage: p = LatticePolytope([(1,0,0), (0,1,0), (0,0,0), ....: (-1,0,0), (0,-1,0), (0,0,0), (0,0,0)]) sage: p 2-d lattice polytope in 3-d lattice M sage: p.vertices() M(-1, 0, 0), M( 0, -1, 0), M( 1, 0, 0), M( 0, 1, 0) in 3-d lattice M
>>> from sage.all import * >>> p = LatticePolytope([(Integer(1),Integer(0),Integer(0)), (Integer(0),Integer(1),Integer(0)), (Integer(0),Integer(0),Integer(0)), ... (-Integer(1),Integer(0),Integer(0)), (Integer(0),-Integer(1),Integer(0)), (Integer(0),Integer(0),Integer(0)), (Integer(0),Integer(0),Integer(0))]) >>> p 2-d lattice polytope in 3-d lattice M >>> p.vertices() M(-1, 0, 0), M( 0, -1, 0), M( 1, 0, 0), M( 0, 1, 0) in 3-d lattice M
An empty lattice polytope can be considered as well:
sage: p = LatticePolytope([], lattice=ToricLattice(3).dual()); p -1-d lattice polytope in 3-d lattice M sage: p.lattice_dim() 3 sage: p.npoints() 0 sage: p.nfacets() 0 sage: p.points() Empty collection in 3-d lattice M sage: p.faces() # needs sage.graphs ((-1-d lattice polytope in 3-d lattice M,),)
>>> from sage.all import * >>> p = LatticePolytope([], lattice=ToricLattice(Integer(3)).dual()); p -1-d lattice polytope in 3-d lattice M >>> p.lattice_dim() 3 >>> p.npoints() 0 >>> p.nfacets() 0 >>> p.points() Empty collection in 3-d lattice M >>> p.faces() # needs sage.graphs ((-1-d lattice polytope in 3-d lattice M,),)
- class sage.geometry.lattice_polytope.LatticePolytopeClass(points=None, compute_vertices=None, ambient=None, ambient_vertex_indices=None, ambient_facet_indices=None)[source]¶
Bases:
ConvexSet_compact,Hashable,LatticePolytopeCreate a lattice polytope.
Warning
This class does not perform any checks of correctness of input nor does it convert input into the standard representation. Use
LatticePolytope()to construct lattice polytopes.Lattice polytopes are immutable, but they cache most of the returned values.
INPUT:
The input can be either:
points–PointCollectioncompute_vertices– boolean
or (these parameters must be given as keywords):
ambient– ambient structure, this polytope must be a face ofambientambient_vertex_indices– increasing list or tuple of integers, indices of vertices ofambientgenerating this polytopeambient_facet_indices– increasing list or tuple of integers, indices of facets ofambientgenerating this polytope
OUTPUT: lattice polytope
Note
Every polytope has an ambient structure. If it was not specified, it is this polytope itself.
- adjacent()[source]¶
Return faces adjacent to
selfin the ambient face lattice.Two distinct faces \(F_1\) and \(F_2\) of the same face lattice are adjacent if all of the following conditions hold:
\(F_1\) and \(F_2\) have the same dimension \(d\);
\(F_1\) and \(F_2\) share a facet of dimension \(d-1\);
\(F_1\) and \(F_2\) are facets of some face of dimension \(d+1\), unless \(d\) is the dimension of the ambient structure.
OUTPUT:
tupleoflattice polytopesEXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: o.adjacent() # needs sage.graphs () sage: face = o.faces(1)[0] # needs sage.graphs sage: face.adjacent() # needs sage.graphs (1-d face of 3-d reflexive polytope in 3-d lattice M, 1-d face of 3-d reflexive polytope in 3-d lattice M, 1-d face of 3-d reflexive polytope in 3-d lattice M, 1-d face of 3-d reflexive polytope in 3-d lattice M)
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.adjacent() # needs sage.graphs () >>> face = o.faces(Integer(1))[Integer(0)] # needs sage.graphs >>> face.adjacent() # needs sage.graphs (1-d face of 3-d reflexive polytope in 3-d lattice M, 1-d face of 3-d reflexive polytope in 3-d lattice M, 1-d face of 3-d reflexive polytope in 3-d lattice M, 1-d face of 3-d reflexive polytope in 3-d lattice M)
- affine_transform(a=1, b=0)[source]¶
Return a*P+b, where P is this lattice polytope.
Note
While
aandbmay be rational, the final result must be a lattice polytope, i.e. all vertices must be integral.If the transform (restricted to this polytope) is bijective, facial structure will be preserved, e.g. the first facet of the image will be spanned by the images of vertices which span the first facet of the original polytope.
INPUT:
a– (default: 1) rational scalar or matrixb– (default: 0) rational scalar or vector, scalars are interpreted as vectors with the same components
EXAMPLES:
sage: o = lattice_polytope.cross_polytope(2) sage: o.vertices() M( 1, 0), M( 0, 1), M(-1, 0), M( 0, -1) in 2-d lattice M sage: o.affine_transform(2).vertices() M( 2, 0), M( 0, 2), M(-2, 0), M( 0, -2) in 2-d lattice M sage: o.affine_transform(1,1).vertices() M(2, 1), M(1, 2), M(0, 1), M(1, 0) in 2-d lattice M sage: o.affine_transform(b=1).vertices() M(2, 1), M(1, 2), M(0, 1), M(1, 0) in 2-d lattice M sage: o.affine_transform(b=(1, 0)).vertices() M(2, 0), M(1, 1), M(0, 0), M(1, -1) in 2-d lattice M sage: a = matrix(QQ, 2, [1/2, 0, 0, 3/2]) sage: o.polar().vertices() N( 1, 1), N( 1, -1), N(-1, -1), N(-1, 1) in 2-d lattice N sage: o.polar().affine_transform(a, (1/2, -1/2)).vertices() M(1, 1), M(1, -2), M(0, -2), M(0, 1) in 2-d lattice M
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(2)) >>> o.vertices() M( 1, 0), M( 0, 1), M(-1, 0), M( 0, -1) in 2-d lattice M >>> o.affine_transform(Integer(2)).vertices() M( 2, 0), M( 0, 2), M(-2, 0), M( 0, -2) in 2-d lattice M >>> o.affine_transform(Integer(1),Integer(1)).vertices() M(2, 1), M(1, 2), M(0, 1), M(1, 0) in 2-d lattice M >>> o.affine_transform(b=Integer(1)).vertices() M(2, 1), M(1, 2), M(0, 1), M(1, 0) in 2-d lattice M >>> o.affine_transform(b=(Integer(1), Integer(0))).vertices() M(2, 0), M(1, 1), M(0, 0), M(1, -1) in 2-d lattice M >>> a = matrix(QQ, Integer(2), [Integer(1)/Integer(2), Integer(0), Integer(0), Integer(3)/Integer(2)]) >>> o.polar().vertices() N( 1, 1), N( 1, -1), N(-1, -1), N(-1, 1) in 2-d lattice N >>> o.polar().affine_transform(a, (Integer(1)/Integer(2), -Integer(1)/Integer(2))).vertices() M(1, 1), M(1, -2), M(0, -2), M(0, 1) in 2-d lattice M
While you can use rational transformation, the result must be integer:
sage: o.affine_transform(a) Traceback (most recent call last): ... ValueError: points [(1/2, 0), (0, 3/2), (-1/2, 0), (0, -3/2)] are not in 2-d lattice M!
>>> from sage.all import * >>> o.affine_transform(a) Traceback (most recent call last): ... ValueError: points [(1/2, 0), (0, 3/2), (-1/2, 0), (0, -3/2)] are not in 2-d lattice M!
- ambient()[source]¶
Return the ambient structure of
self.OUTPUT: lattice polytope containing
selfas a faceEXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: o.ambient() 3-d reflexive polytope in 3-d lattice M sage: o.ambient() is o True sage: # needs sage.graphs sage: face = o.faces(1)[0] sage: face 1-d face of 3-d reflexive polytope in 3-d lattice M sage: face.ambient() 3-d reflexive polytope in 3-d lattice M sage: face.ambient() is o True
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.ambient() 3-d reflexive polytope in 3-d lattice M >>> o.ambient() is o True >>> # needs sage.graphs >>> face = o.faces(Integer(1))[Integer(0)] >>> face 1-d face of 3-d reflexive polytope in 3-d lattice M >>> face.ambient() 3-d reflexive polytope in 3-d lattice M >>> face.ambient() is o True
- ambient_dim()[source]¶
Return the dimension of the ambient lattice of
self.An alias is
ambient_dim().OUTPUT: integer
EXAMPLES:
sage: p = LatticePolytope([(1,0)]) sage: p.lattice_dim() 2 sage: p.dim() 0
>>> from sage.all import * >>> p = LatticePolytope([(Integer(1),Integer(0))]) >>> p.lattice_dim() 2 >>> p.dim() 0
- ambient_facet_indices()[source]¶
Return indices of facets of the ambient polytope containing
self.OUTPUT: increasing
tupleof integersEXAMPLES:
The polytope itself is not contained in any of its facets:
sage: o = lattice_polytope.cross_polytope(3) sage: o.ambient_facet_indices() ()
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.ambient_facet_indices() ()
But each of its other faces is contained in one or more facets:
sage: # needs sage.graphs sage: face = o.faces(1)[0] sage: face.ambient_facet_indices() (4, 5) sage: face.vertices() M(1, 0, 0), M(0, 1, 0) in 3-d lattice M sage: o.facets()[face.ambient_facet_indices()[0]].vertices() M(1, 0, 0), M(0, 1, 0), M(0, 0, -1) in 3-d lattice M
>>> from sage.all import * >>> # needs sage.graphs >>> face = o.faces(Integer(1))[Integer(0)] >>> face.ambient_facet_indices() (4, 5) >>> face.vertices() M(1, 0, 0), M(0, 1, 0) in 3-d lattice M >>> o.facets()[face.ambient_facet_indices()[Integer(0)]].vertices() M(1, 0, 0), M(0, 1, 0), M(0, 0, -1) in 3-d lattice M
- ambient_ordered_point_indices()[source]¶
Return indices of points of the ambient polytope contained in this one.
OUTPUT:
tupleof integers such that ambient points in this order are geometrically ordered, e.g. for an edge points will appear from one end point to the other.
EXAMPLES:
sage: cube = lattice_polytope.cross_polytope(3).polar() sage: face = cube.facets()[0] # needs sage.graphs sage: face.ambient_ordered_point_indices() # needs palp sage.graphs (5, 8, 4, 9, 10, 11, 6, 12, 7) sage: cube.points(face.ambient_ordered_point_indices()) # needs palp sage.graphs N(-1, -1, -1), N(-1, -1, 0), N(-1, -1, 1), N(-1, 0, -1), N(-1, 0, 0), N(-1, 0, 1), N(-1, 1, -1), N(-1, 1, 0), N(-1, 1, 1) in 3-d lattice N
>>> from sage.all import * >>> cube = lattice_polytope.cross_polytope(Integer(3)).polar() >>> face = cube.facets()[Integer(0)] # needs sage.graphs >>> face.ambient_ordered_point_indices() # needs palp sage.graphs (5, 8, 4, 9, 10, 11, 6, 12, 7) >>> cube.points(face.ambient_ordered_point_indices()) # needs palp sage.graphs N(-1, -1, -1), N(-1, -1, 0), N(-1, -1, 1), N(-1, 0, -1), N(-1, 0, 0), N(-1, 0, 1), N(-1, 1, -1), N(-1, 1, 0), N(-1, 1, 1) in 3-d lattice N
- ambient_point_indices()[source]¶
Return indices of points of the ambient polytope contained in this one.
OUTPUT:
tupleof integers, the order corresponds to the order of points of this polytope.
EXAMPLES:
sage: cube = lattice_polytope.cross_polytope(3).polar() sage: face = cube.facets()[0] # needs sage.graphs sage: face.ambient_point_indices() # needs palp sage.graphs (4, 5, 6, 7, 8, 9, 10, 11, 12) sage: cube.points(face.ambient_point_indices()) == face.points() # needs palp sage.graphs True
>>> from sage.all import * >>> cube = lattice_polytope.cross_polytope(Integer(3)).polar() >>> face = cube.facets()[Integer(0)] # needs sage.graphs >>> face.ambient_point_indices() # needs palp sage.graphs (4, 5, 6, 7, 8, 9, 10, 11, 12) >>> cube.points(face.ambient_point_indices()) == face.points() # needs palp sage.graphs True
- ambient_vector_space(base_field=None)[source]¶
Return the ambient vector space.
It is the ambient lattice (
lattice()) tensored with a field.INPUT:
base_field– (default: the rationals) a field
EXAMPLES:
sage: p = LatticePolytope([(1,0)]) sage: p.ambient_vector_space() Vector space of dimension 2 over Rational Field sage: p.ambient_vector_space(AA) # needs sage.rings.number_field Vector space of dimension 2 over Algebraic Real Field
>>> from sage.all import * >>> p = LatticePolytope([(Integer(1),Integer(0))]) >>> p.ambient_vector_space() Vector space of dimension 2 over Rational Field >>> p.ambient_vector_space(AA) # needs sage.rings.number_field Vector space of dimension 2 over Algebraic Real Field
- ambient_vertex_indices()[source]¶
Return indices of vertices of the ambient structure generating
self.OUTPUT: increasing
tupleof integersEXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: o.ambient_vertex_indices() (0, 1, 2, 3, 4, 5) sage: face = o.faces(1)[0] # needs sage.graphs sage: face.ambient_vertex_indices() # needs sage.graphs (0, 1)
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.ambient_vertex_indices() (0, 1, 2, 3, 4, 5) >>> face = o.faces(Integer(1))[Integer(0)] # needs sage.graphs >>> face.ambient_vertex_indices() # needs sage.graphs (0, 1)
- boundary_point_indices()[source]¶
Return indices of (relative) boundary lattice points of this polytope.
OUTPUT: increasing
tupleof integersEXAMPLES:
All points but the origin are on the boundary of this square:
sage: square = lattice_polytope.cross_polytope(2).polar() sage: square.points() # needs palp N( 1, 1), N( 1, -1), N(-1, -1), N(-1, 1), N(-1, 0), N( 0, -1), N( 0, 0), N( 0, 1), N( 1, 0) in 2-d lattice N sage: square.boundary_point_indices() # needs palp (0, 1, 2, 3, 4, 5, 7, 8)
>>> from sage.all import * >>> square = lattice_polytope.cross_polytope(Integer(2)).polar() >>> square.points() # needs palp N( 1, 1), N( 1, -1), N(-1, -1), N(-1, 1), N(-1, 0), N( 0, -1), N( 0, 0), N( 0, 1), N( 1, 0) in 2-d lattice N >>> square.boundary_point_indices() # needs palp (0, 1, 2, 3, 4, 5, 7, 8)
For an edge the boundary is formed by the end points:
sage: face = square.edges()[0] # needs sage.graphs sage: face.points() # needs sage.graphs N(-1, -1), N(-1, 1), N(-1, 0) in 2-d lattice N sage: face.boundary_point_indices() # needs sage.graphs (0, 1)
>>> from sage.all import * >>> face = square.edges()[Integer(0)] # needs sage.graphs >>> face.points() # needs sage.graphs N(-1, -1), N(-1, 1), N(-1, 0) in 2-d lattice N >>> face.boundary_point_indices() # needs sage.graphs (0, 1)
- boundary_points()[source]¶
Return (relative) boundary lattice points of this polytope.
OUTPUT: a
point collectionEXAMPLES:
All points but the origin are on the boundary of this square:
sage: square = lattice_polytope.cross_polytope(2).polar() sage: square.boundary_points() # needs palp N( 1, 1), N( 1, -1), N(-1, -1), N(-1, 1), N(-1, 0), N( 0, -1), N( 0, 1), N( 1, 0) in 2-d lattice N
>>> from sage.all import * >>> square = lattice_polytope.cross_polytope(Integer(2)).polar() >>> square.boundary_points() # needs palp N( 1, 1), N( 1, -1), N(-1, -1), N(-1, 1), N(-1, 0), N( 0, -1), N( 0, 1), N( 1, 0) in 2-d lattice N
For an edge the boundary is formed by the end points:
sage: face = square.edges()[0] # needs sage.graphs sage: face.boundary_points() # needs sage.graphs N(-1, -1), N(-1, 1) in 2-d lattice N
>>> from sage.all import * >>> face = square.edges()[Integer(0)] # needs sage.graphs >>> face.boundary_points() # needs sage.graphs N(-1, -1), N(-1, 1) in 2-d lattice N
- contains(*args)[source]¶
Check if a given point is contained in
self.INPUT:
an attempt will be made to convert all arguments into a single element of the ambient space of
self; if it fails,Falsewill be returned
OUTPUT:
Trueif the given point is contained inself,Falseotherwise
EXAMPLES:
sage: p = lattice_polytope.cross_polytope(2) sage: p.contains(p.lattice()(1,0)) True sage: p.contains((1,0)) True sage: p.contains(1,0) True sage: p.contains((2,0)) False
>>> from sage.all import * >>> p = lattice_polytope.cross_polytope(Integer(2)) >>> p.contains(p.lattice()(Integer(1),Integer(0))) True >>> p.contains((Integer(1),Integer(0))) True >>> p.contains(Integer(1),Integer(0)) True >>> p.contains((Integer(2),Integer(0))) False
- dim()[source]¶
Return the dimension of this polytope.
EXAMPLES:
We create a 3-dimensional octahedron and check its dimension:
sage: o = lattice_polytope.cross_polytope(3) sage: o.dim() 3
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.dim() 3
Now we create a 2-dimensional diamond in a 3-dimensional space:
sage: p = LatticePolytope([(1,0,0), (0,1,0), (-1,0,0), (0,-1,0)]) sage: p.dim() 2 sage: p.lattice_dim() 3
>>> from sage.all import * >>> p = LatticePolytope([(Integer(1),Integer(0),Integer(0)), (Integer(0),Integer(1),Integer(0)), (-Integer(1),Integer(0),Integer(0)), (Integer(0),-Integer(1),Integer(0))]) >>> p.dim() 2 >>> p.lattice_dim() 3
- distances(point=None)[source]¶
Return the matrix of distances for this polytope or distances for the given point.
The matrix of distances m gives distances m[i,j] between the \(i\)-th facet (which is also the \(i\)-th vertex of the polar polytope in the reflexive case) and \(j\)-th point of this polytope.
If point is specified, integral distances from the point to all facets of this polytope will be computed.
EXAMPLES: The matrix of distances for a 3-dimensional octahedron:
sage: o = lattice_polytope.cross_polytope(3) sage: o.distances() # needs palp [2 0 0 0 2 2 1] [2 2 0 0 0 2 1] [2 2 2 0 0 0 1] [2 0 2 0 2 0 1] [0 0 2 2 2 0 1] [0 0 0 2 2 2 1] [0 2 0 2 0 2 1] [0 2 2 2 0 0 1]
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.distances() # needs palp [2 0 0 0 2 2 1] [2 2 0 0 0 2 1] [2 2 2 0 0 0 1] [2 0 2 0 2 0 1] [0 0 2 2 2 0 1] [0 0 0 2 2 2 1] [0 2 0 2 0 2 1] [0 2 2 2 0 0 1]
Distances from facets to the point (1,2,3):
sage: o.distances([1,2,3]) (-3, 1, 7, 3, 1, -5, -1, 5)
>>> from sage.all import * >>> o.distances([Integer(1),Integer(2),Integer(3)]) (-3, 1, 7, 3, 1, -5, -1, 5)
It is OK to use RATIONAL coordinates:
sage: o.distances([1,2,3/2]) (-3/2, 5/2, 11/2, 3/2, -1/2, -7/2, 1/2, 7/2) sage: o.distances([1,2,sqrt(2)]) # needs sage.symbolic Traceback (most recent call last): ... TypeError: unable to convert sqrt(2) to an element of Rational Field
>>> from sage.all import * >>> o.distances([Integer(1),Integer(2),Integer(3)/Integer(2)]) (-3/2, 5/2, 11/2, 3/2, -1/2, -7/2, 1/2, 7/2) >>> o.distances([Integer(1),Integer(2),sqrt(Integer(2))]) # needs sage.symbolic Traceback (most recent call last): ... TypeError: unable to convert sqrt(2) to an element of Rational Field
Now we create a non-spanning polytope:
sage: p = LatticePolytope([(1,0,0), (0,1,0), (-1,0,0), (0,-1,0)]) sage: p.distances() # needs palp [2 2 0 0 1] [2 0 0 2 1] [0 0 2 2 1] [0 2 2 0 1] sage: p.distances((1/2, 3, 0)) # needs palp (9/2, -3/2, -5/2, 7/2)
>>> from sage.all import * >>> p = LatticePolytope([(Integer(1),Integer(0),Integer(0)), (Integer(0),Integer(1),Integer(0)), (-Integer(1),Integer(0),Integer(0)), (Integer(0),-Integer(1),Integer(0))]) >>> p.distances() # needs palp [2 2 0 0 1] [2 0 0 2 1] [0 0 2 2 1] [0 2 2 0 1] >>> p.distances((Integer(1)/Integer(2), Integer(3), Integer(0))) # needs palp (9/2, -3/2, -5/2, 7/2)
This point is not even in the affine subspace of the polytope:
sage: p.distances((1, 1, 1)) # needs palp (3, 1, -1, 1)
>>> from sage.all import * >>> p.distances((Integer(1), Integer(1), Integer(1))) # needs palp (3, 1, -1, 1)
- dual()[source]¶
Return the dual face under face duality of polar reflexive polytopes.
This duality extends the correspondence between vertices and facets.
OUTPUT: a
lattice polytopeEXAMPLES:
sage: # needs sage.graphs sage: o = lattice_polytope.cross_polytope(4) sage: e = o.edges()[0]; e 1-d face of 4-d reflexive polytope in 4-d lattice M sage: ed = e.dual(); ed 2-d face of 4-d reflexive polytope in 4-d lattice N sage: ed.ambient() is e.ambient().polar() True sage: e.ambient_vertex_indices() == ed.ambient_facet_indices() True sage: e.ambient_facet_indices() == ed.ambient_vertex_indices() True
>>> from sage.all import * >>> # needs sage.graphs >>> o = lattice_polytope.cross_polytope(Integer(4)) >>> e = o.edges()[Integer(0)]; e 1-d face of 4-d reflexive polytope in 4-d lattice M >>> ed = e.dual(); ed 2-d face of 4-d reflexive polytope in 4-d lattice N >>> ed.ambient() is e.ambient().polar() True >>> e.ambient_vertex_indices() == ed.ambient_facet_indices() True >>> e.ambient_facet_indices() == ed.ambient_vertex_indices() True
- dual_lattice()[source]¶
Return the dual of the ambient lattice of
self.OUTPUT:
a lattice. If possible (that is, if
lattice()has adual()method), the dual lattice is returned. Otherwise, \(\ZZ^n\) is returned, where \(n\) is the dimension ofself.
EXAMPLES:
sage: LatticePolytope([(1,0)]).dual_lattice() 2-d lattice N sage: LatticePolytope([], lattice=ZZ^3).dual_lattice() Ambient free module of rank 3 over the principal ideal domain Integer Ring
>>> from sage.all import * >>> LatticePolytope([(Integer(1),Integer(0))]).dual_lattice() 2-d lattice N >>> LatticePolytope([], lattice=ZZ**Integer(3)).dual_lattice() Ambient free module of rank 3 over the principal ideal domain Integer Ring
- edges()[source]¶
Return edges (faces of dimension 1) of
self.OUTPUT:
tupleoflattice polytopesEXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: o.edges() # needs sage.graphs (1-d face of 3-d reflexive polytope in 3-d lattice M, ... 1-d face of 3-d reflexive polytope in 3-d lattice M) sage: len(o.edges()) # needs sage.graphs 12
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.edges() # needs sage.graphs (1-d face of 3-d reflexive polytope in 3-d lattice M, ... 1-d face of 3-d reflexive polytope in 3-d lattice M) >>> len(o.edges()) # needs sage.graphs 12
- face_lattice()[source]¶
Return the face lattice of
self.This lattice will have the empty polytope as the bottom and this polytope itself as the top.
OUTPUT:
EXAMPLES:
Let’s take a look at the face lattice of a square:
sage: square = LatticePolytope([(0,0), (1,0), (1,1), (0,1)]) sage: L = square.face_lattice(); L # needs sage.graphs Finite lattice containing 10 elements with distinguished linear extension
>>> from sage.all import * >>> square = LatticePolytope([(Integer(0),Integer(0)), (Integer(1),Integer(0)), (Integer(1),Integer(1)), (Integer(0),Integer(1))]) >>> L = square.face_lattice(); L # needs sage.graphs Finite lattice containing 10 elements with distinguished linear extension
To see all faces arranged by dimension, you can do this:
sage: for level in L.level_sets(): print(level) # needs sage.graphs [-1-d face of 2-d lattice polytope in 2-d lattice M] [0-d face of 2-d lattice polytope in 2-d lattice M, 0-d face of 2-d lattice polytope in 2-d lattice M, 0-d face of 2-d lattice polytope in 2-d lattice M, 0-d face of 2-d lattice polytope in 2-d lattice M] [1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M] [2-d lattice polytope in 2-d lattice M]
>>> from sage.all import * >>> for level in L.level_sets(): print(level) # needs sage.graphs [-1-d face of 2-d lattice polytope in 2-d lattice M] [0-d face of 2-d lattice polytope in 2-d lattice M, 0-d face of 2-d lattice polytope in 2-d lattice M, 0-d face of 2-d lattice polytope in 2-d lattice M, 0-d face of 2-d lattice polytope in 2-d lattice M] [1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M] [2-d lattice polytope in 2-d lattice M]
For a particular face you can look at its actual vertices…
sage: face = L.level_sets()[1][0] # needs sage.graphs sage: face.vertices() # needs sage.graphs M(0, 0) in 2-d lattice M
>>> from sage.all import * >>> face = L.level_sets()[Integer(1)][Integer(0)] # needs sage.graphs >>> face.vertices() # needs sage.graphs M(0, 0) in 2-d lattice M
… or you can see the index of the vertex of the original polytope that corresponds to the above one:
sage: face.ambient_vertex_indices() # needs sage.graphs (0,) sage: square.vertex(0) M(0, 0)
>>> from sage.all import * >>> face.ambient_vertex_indices() # needs sage.graphs (0,) >>> square.vertex(Integer(0)) M(0, 0)
An alternative to extracting faces from the face lattice is to use
faces()method:sage: face is square.faces(dim=0)[0] # needs sage.graphs True
>>> from sage.all import * >>> face is square.faces(dim=Integer(0))[Integer(0)] # needs sage.graphs True
The advantage of working with the face lattice directly is that you can (relatively easily) get faces that are related to the given one:
sage: face = L.level_sets()[1][0] # needs sage.graphs sage: D = L.hasse_diagram() # needs sage.graphs sage: sorted(D.neighbors(face)) # needs sage.graphs [-1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M]
>>> from sage.all import * >>> face = L.level_sets()[Integer(1)][Integer(0)] # needs sage.graphs >>> D = L.hasse_diagram() # needs sage.graphs >>> sorted(D.neighbors(face)) # needs sage.graphs [-1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M]
However, you can achieve some of this functionality using
facets(),facet_of(), andadjacent()methods:sage: # needs sage.graphs sage: face = square.faces(0)[0] sage: face 0-d face of 2-d lattice polytope in 2-d lattice M sage: face.vertices() M(0, 0) in 2-d lattice M sage: face.facets() (-1-d face of 2-d lattice polytope in 2-d lattice M,) sage: face.facet_of() (1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M) sage: face.adjacent() (0-d face of 2-d lattice polytope in 2-d lattice M, 0-d face of 2-d lattice polytope in 2-d lattice M) sage: face.adjacent()[0].vertices() M(1, 0) in 2-d lattice M
>>> from sage.all import * >>> # needs sage.graphs >>> face = square.faces(Integer(0))[Integer(0)] >>> face 0-d face of 2-d lattice polytope in 2-d lattice M >>> face.vertices() M(0, 0) in 2-d lattice M >>> face.facets() (-1-d face of 2-d lattice polytope in 2-d lattice M,) >>> face.facet_of() (1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M) >>> face.adjacent() (0-d face of 2-d lattice polytope in 2-d lattice M, 0-d face of 2-d lattice polytope in 2-d lattice M) >>> face.adjacent()[Integer(0)].vertices() M(1, 0) in 2-d lattice M
Note that if
pis a face ofsuperp, then the face lattice ofpconsists of (appropriate) faces ofsuperp:sage: # needs sage.graphs sage: superp = LatticePolytope([(1,2,3,4), (5,6,7,8), ....: (1,2,4,8), (1,3,9,7)]) sage: superp.face_lattice() Finite lattice containing 16 elements with distinguished linear extension sage: superp.face_lattice().top() 3-d lattice polytope in 4-d lattice M sage: p = superp.facets()[0] sage: p 2-d face of 3-d lattice polytope in 4-d lattice M sage: p.face_lattice() Finite poset containing 8 elements with distinguished linear extension sage: p.face_lattice().bottom() -1-d face of 3-d lattice polytope in 4-d lattice M sage: p.face_lattice().top() 2-d face of 3-d lattice polytope in 4-d lattice M sage: p.face_lattice().top() is p True
>>> from sage.all import * >>> # needs sage.graphs >>> superp = LatticePolytope([(Integer(1),Integer(2),Integer(3),Integer(4)), (Integer(5),Integer(6),Integer(7),Integer(8)), ... (Integer(1),Integer(2),Integer(4),Integer(8)), (Integer(1),Integer(3),Integer(9),Integer(7))]) >>> superp.face_lattice() Finite lattice containing 16 elements with distinguished linear extension >>> superp.face_lattice().top() 3-d lattice polytope in 4-d lattice M >>> p = superp.facets()[Integer(0)] >>> p 2-d face of 3-d lattice polytope in 4-d lattice M >>> p.face_lattice() Finite poset containing 8 elements with distinguished linear extension >>> p.face_lattice().bottom() -1-d face of 3-d lattice polytope in 4-d lattice M >>> p.face_lattice().top() 2-d face of 3-d lattice polytope in 4-d lattice M >>> p.face_lattice().top() is p True
- faces(dim=None, codim=None)[source]¶
Return faces of
selfof specified (co)dimension.INPUT:
dim– integer; dimension of the requested facescodim– integer; codimension of the requested faces
Note
You can specify at most one parameter. If you don’t give any, then all faces will be returned.
OUTPUT:
if either
dimorcodimis given, the output will be atupleoflattice polytopes;if neither
dimnorcodimis given, the output will be thetupleof tuples as above, giving faces of all existing dimensions. If you care about inclusion relations between faces, consider usingface_lattice()oradjacent(),facet_of(), andfacets().
EXAMPLES:
Let’s take a look at the faces of a square:
sage: square = LatticePolytope([(0,0), (1,0), (1,1), (0,1)]) sage: square.faces() # needs sage.graphs ((-1-d face of 2-d lattice polytope in 2-d lattice M,), (0-d face of 2-d lattice polytope in 2-d lattice M, 0-d face of 2-d lattice polytope in 2-d lattice M, 0-d face of 2-d lattice polytope in 2-d lattice M, 0-d face of 2-d lattice polytope in 2-d lattice M), (1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M), (2-d lattice polytope in 2-d lattice M,))
>>> from sage.all import * >>> square = LatticePolytope([(Integer(0),Integer(0)), (Integer(1),Integer(0)), (Integer(1),Integer(1)), (Integer(0),Integer(1))]) >>> square.faces() # needs sage.graphs ((-1-d face of 2-d lattice polytope in 2-d lattice M,), (0-d face of 2-d lattice polytope in 2-d lattice M, 0-d face of 2-d lattice polytope in 2-d lattice M, 0-d face of 2-d lattice polytope in 2-d lattice M, 0-d face of 2-d lattice polytope in 2-d lattice M), (1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M), (2-d lattice polytope in 2-d lattice M,))
Its faces of dimension one (i.e., edges):
sage: square.faces(dim=1) # needs sage.graphs (1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M)
>>> from sage.all import * >>> square.faces(dim=Integer(1)) # needs sage.graphs (1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M, 1-d face of 2-d lattice polytope in 2-d lattice M)
Its faces of codimension one are the same (also edges):
sage: square.faces(codim=1) is square.faces(dim=1) # needs sage.graphs True
>>> from sage.all import * >>> square.faces(codim=Integer(1)) is square.faces(dim=Integer(1)) # needs sage.graphs True
Let’s pick a particular face:
sage: face = square.faces(dim=1)[0] # needs sage.graphs
>>> from sage.all import * >>> face = square.faces(dim=Integer(1))[Integer(0)] # needs sage.graphs
Now you can look at the actual vertices of this face…
sage: face.vertices() # needs sage.graphs M(0, 0), M(0, 1) in 2-d lattice M
>>> from sage.all import * >>> face.vertices() # needs sage.graphs M(0, 0), M(0, 1) in 2-d lattice M
… or you can see indices of the vertices of the original polytope that correspond to the above ones:
sage: face.ambient_vertex_indices() # needs sage.graphs (0, 3) sage: square.vertices(face.ambient_vertex_indices()) # needs sage.graphs M(0, 0), M(0, 1) in 2-d lattice M
>>> from sage.all import * >>> face.ambient_vertex_indices() # needs sage.graphs (0, 3) >>> square.vertices(face.ambient_vertex_indices()) # needs sage.graphs M(0, 0), M(0, 1) in 2-d lattice M
- facet_constant(i)[source]¶
Return the constant in the \(i\)-th facet inequality of this polytope.
This is equivalent to
facet_constants()[i].INPUT:
i– integer; the index of the facet
OUTPUT: integer; the constant in the \(i\)-th facet inequality
See also
facet_constants(),facet_normal(),facet_normals(),facets().EXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: o.facet_constant(0) 1 sage: o.facet_constant(0) == o.facet_constants()[0] True
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.facet_constant(Integer(0)) 1 >>> o.facet_constant(Integer(0)) == o.facet_constants()[Integer(0)] True
- facet_constants()[source]¶
Return facet constants of
self.Facet inequalities have form \(n \cdot x + c \geq 0\) where \(n\) is the inner normal and \(c\) is a constant.
OUTPUT: integer vector
See also
facet_constant(),facet_normal(),facet_normals(),facets().EXAMPLES:
For reflexive polytopes all constants are 1:
sage: o = lattice_polytope.cross_polytope(3) sage: o.vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M sage: o.facet_constants() (1, 1, 1, 1, 1, 1, 1, 1)
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M >>> o.facet_constants() (1, 1, 1, 1, 1, 1, 1, 1)
Here is an example of a 3-dimensional polytope in a 4-dimensional space with 3 facets containing the origin:
sage: p = LatticePolytope([(0,0,0,0), (1,1,1,3), ....: (1,-1,1,3), (-1,-1,1,3)]) sage: p.vertices() M( 0, 0, 0, 0), M( 1, 1, 1, 3), M( 1, -1, 1, 3), M(-1, -1, 1, 3) in 4-d lattice M sage: p.facet_constants() (0, 0, 3, 0)
>>> from sage.all import * >>> p = LatticePolytope([(Integer(0),Integer(0),Integer(0),Integer(0)), (Integer(1),Integer(1),Integer(1),Integer(3)), ... (Integer(1),-Integer(1),Integer(1),Integer(3)), (-Integer(1),-Integer(1),Integer(1),Integer(3))]) >>> p.vertices() M( 0, 0, 0, 0), M( 1, 1, 1, 3), M( 1, -1, 1, 3), M(-1, -1, 1, 3) in 4-d lattice M >>> p.facet_constants() (0, 0, 3, 0)
- facet_normal(i)[source]¶
Return the inner normal to the
i-th facet of this polytope.This is equivalent to
facet_normals()[i].INPUT:
i– integer; the index of the facet
OUTPUT: a vector
See also
facet_constant(),facet_constants(),facet_normals(),facets().EXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: o.facet_normal(0) N(1, -1, -1) sage: o.facet_normal(0) is o.facet_normals()[0] True
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.facet_normal(Integer(0)) N(1, -1, -1) >>> o.facet_normal(Integer(0)) is o.facet_normals()[Integer(0)] True
- facet_normals()[source]¶
Return inner normals to the facets of
self.If this polytope is not full-dimensional, facet normals will define this polytope in the affine subspace spanned by it.
OUTPUT:
a
point collectionin thedual_lattice()ofself.
See also
facet_constant(),facet_constants(),facet_normal(),facets().EXAMPLES:
Normals to facets of an octahedron are vertices of a cube:
sage: o = lattice_polytope.cross_polytope(3) sage: o.vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M sage: o.facet_normals() N( 1, -1, -1), N( 1, 1, -1), N( 1, 1, 1), N( 1, -1, 1), N(-1, -1, 1), N(-1, -1, -1), N(-1, 1, -1), N(-1, 1, 1) in 3-d lattice N
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M >>> o.facet_normals() N( 1, -1, -1), N( 1, 1, -1), N( 1, 1, 1), N( 1, -1, 1), N(-1, -1, 1), N(-1, -1, -1), N(-1, 1, -1), N(-1, 1, 1) in 3-d lattice N
Here is an example of a 3-dimensional polytope in a 4-dimensional space:
sage: p = LatticePolytope([(0,0,0,0), (1,1,1,3), ....: (1,-1,1,3), (-1,-1,1,3)]) sage: p.vertices() M( 0, 0, 0, 0), M( 1, 1, 1, 3), M( 1, -1, 1, 3), M(-1, -1, 1, 3) in 4-d lattice M sage: p.facet_normals() N( 0, 3, 0, 1), N( 1, -1, 0, 0), N( 0, 0, 0, -1), N(-3, 0, 0, 1) in 4-d lattice N sage: p.facet_constants() (0, 0, 3, 0)
>>> from sage.all import * >>> p = LatticePolytope([(Integer(0),Integer(0),Integer(0),Integer(0)), (Integer(1),Integer(1),Integer(1),Integer(3)), ... (Integer(1),-Integer(1),Integer(1),Integer(3)), (-Integer(1),-Integer(1),Integer(1),Integer(3))]) >>> p.vertices() M( 0, 0, 0, 0), M( 1, 1, 1, 3), M( 1, -1, 1, 3), M(-1, -1, 1, 3) in 4-d lattice M >>> p.facet_normals() N( 0, 3, 0, 1), N( 1, -1, 0, 0), N( 0, 0, 0, -1), N(-3, 0, 0, 1) in 4-d lattice N >>> p.facet_constants() (0, 0, 3, 0)
Now we manually compute the distance matrix of this polytope. Since it is a simplex, each line (corresponding to a facet) should consist of zeros (indicating generating vertices of the corresponding facet) and a single positive number (since our normals are inner):
sage: matrix([[n * v + c for v in p.vertices()] ....: for n, c in zip(p.facet_normals(), p.facet_constants())]) [0 6 0 0] [0 0 2 0] [3 0 0 0] [0 0 0 6]
>>> from sage.all import * >>> matrix([[n * v + c for v in p.vertices()] ... for n, c in zip(p.facet_normals(), p.facet_constants())]) [0 6 0 0] [0 0 2 0] [3 0 0 0] [0 0 0 6]
- facet_of()[source]¶
Return elements of the ambient face lattice having
selfas a facet.OUTPUT:
tupleoflattice polytopesEXAMPLES:
sage: # needs sage.graphs sage: square = LatticePolytope([(0,0), (1,0), (1,1), (0,1)]) sage: square.facet_of() () sage: face = square.faces(0)[0] sage: len(face.facet_of()) 2 sage: face.facet_of()[1] 1-d face of 2-d lattice polytope in 2-d lattice M
>>> from sage.all import * >>> # needs sage.graphs >>> square = LatticePolytope([(Integer(0),Integer(0)), (Integer(1),Integer(0)), (Integer(1),Integer(1)), (Integer(0),Integer(1))]) >>> square.facet_of() () >>> face = square.faces(Integer(0))[Integer(0)] >>> len(face.facet_of()) 2 >>> face.facet_of()[Integer(1)] 1-d face of 2-d lattice polytope in 2-d lattice M
- facets()[source]¶
Return facets (faces of codimension 1) of
self.OUTPUT:
tupleoflattice polytopesEXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: o.facets() # needs sage.graphs (2-d face of 3-d reflexive polytope in 3-d lattice M, ... 2-d face of 3-d reflexive polytope in 3-d lattice M) sage: len(o.facets()) # needs sage.graphs 8
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.facets() # needs sage.graphs (2-d face of 3-d reflexive polytope in 3-d lattice M, ... 2-d face of 3-d reflexive polytope in 3-d lattice M) >>> len(o.facets()) # needs sage.graphs 8
- incidence_matrix()[source]¶
Return the incidence matrix.
Note
The columns correspond to facets/facet normals in the order of
facet_normals(), the rows correspond to the vertices in the order ofvertices().EXAMPLES:
sage: o = lattice_polytope.cross_polytope(2) sage: o.incidence_matrix() [0 0 1 1] [0 1 1 0] [1 1 0 0] [1 0 0 1] sage: o.faces(1)[0].incidence_matrix() # needs sage.graphs [1 0] [0 1] sage: o = lattice_polytope.cross_polytope(4) sage: o.incidence_matrix().column(3).nonzero_positions() [3, 4, 5, 6] sage: o.facets()[3].ambient_vertex_indices() # needs sage.graphs (3, 4, 5, 6)
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(2)) >>> o.incidence_matrix() [0 0 1 1] [0 1 1 0] [1 1 0 0] [1 0 0 1] >>> o.faces(Integer(1))[Integer(0)].incidence_matrix() # needs sage.graphs [1 0] [0 1] >>> o = lattice_polytope.cross_polytope(Integer(4)) >>> o.incidence_matrix().column(Integer(3)).nonzero_positions() [3, 4, 5, 6] >>> o.facets()[Integer(3)].ambient_vertex_indices() # needs sage.graphs (3, 4, 5, 6)
- index()[source]¶
Return the index of this polytope in the internal database of 2- or 3-dimensional reflexive polytopes. Databases are stored in the directory of the package.
Note
The first call to this function for each dimension can take a few seconds while the dictionary of all polytopes is constructed, but after that it is cached and fast.
- Return type:
integer
EXAMPLES: We check what is the index of the “diamond” in the database:
sage: d = lattice_polytope.cross_polytope(2) sage: d.index() # needs palp 3
>>> from sage.all import * >>> d = lattice_polytope.cross_polytope(Integer(2)) >>> d.index() # needs palp 3
Note that polytopes with the same index are not necessarily the same:
sage: d.vertices() M( 1, 0), M( 0, 1), M(-1, 0), M( 0, -1) in 2-d lattice M sage: lattice_polytope.ReflexivePolytope(2,3).vertices() M( 1, 0), M( 0, 1), M( 0, -1), M(-1, 0) in 2-d lattice M
>>> from sage.all import * >>> d.vertices() M( 1, 0), M( 0, 1), M(-1, 0), M( 0, -1) in 2-d lattice M >>> lattice_polytope.ReflexivePolytope(Integer(2),Integer(3)).vertices() M( 1, 0), M( 0, 1), M( 0, -1), M(-1, 0) in 2-d lattice M
But they are in the same \(GL(\ZZ^n)\) orbit and have the same normal form:
sage: d.normal_form() # needs sage.groups M( 1, 0), M( 0, 1), M( 0, -1), M(-1, 0) in 2-d lattice M sage: lattice_polytope.ReflexivePolytope(2,3).normal_form() # needs sage.groups M( 1, 0), M( 0, 1), M( 0, -1), M(-1, 0) in 2-d lattice M
>>> from sage.all import * >>> d.normal_form() # needs sage.groups M( 1, 0), M( 0, 1), M( 0, -1), M(-1, 0) in 2-d lattice M >>> lattice_polytope.ReflexivePolytope(Integer(2),Integer(3)).normal_form() # needs sage.groups M( 1, 0), M( 0, 1), M( 0, -1), M(-1, 0) in 2-d lattice M
- interior_point_indices()[source]¶
Return indices of (relative) interior lattice points of this polytope.
OUTPUT: increasing
tupleof integersEXAMPLES:
The origin is the only interior point of this square:
sage: square = lattice_polytope.cross_polytope(2).polar() sage: square.points() # needs palp N( 1, 1), N( 1, -1), N(-1, -1), N(-1, 1), N(-1, 0), N( 0, -1), N( 0, 0), N( 0, 1), N( 1, 0) in 2-d lattice N sage: square.interior_point_indices() # needs palp (6,)
>>> from sage.all import * >>> square = lattice_polytope.cross_polytope(Integer(2)).polar() >>> square.points() # needs palp N( 1, 1), N( 1, -1), N(-1, -1), N(-1, 1), N(-1, 0), N( 0, -1), N( 0, 0), N( 0, 1), N( 1, 0) in 2-d lattice N >>> square.interior_point_indices() # needs palp (6,)
Its edges also have a single interior point each:
sage: face = square.edges()[0] # needs sage.graphs sage: face.points() # needs sage.graphs N(-1, -1), N(-1, 1), N(-1, 0) in 2-d lattice N sage: face.interior_point_indices() # needs sage.graphs (2,)
>>> from sage.all import * >>> face = square.edges()[Integer(0)] # needs sage.graphs >>> face.points() # needs sage.graphs N(-1, -1), N(-1, 1), N(-1, 0) in 2-d lattice N >>> face.interior_point_indices() # needs sage.graphs (2,)
- interior_points()[source]¶
Return (relative) boundary lattice points of this polytope.
OUTPUT: a
point collectionEXAMPLES:
The origin is the only interior point of this square:
sage: square = lattice_polytope.cross_polytope(2).polar() sage: square.interior_points() # needs palp N(0, 0) in 2-d lattice N
>>> from sage.all import * >>> square = lattice_polytope.cross_polytope(Integer(2)).polar() >>> square.interior_points() # needs palp N(0, 0) in 2-d lattice N
Its edges also have a single interior point each:
sage: face = square.edges()[0] # needs sage.graphs sage: face.interior_points() # needs sage.graphs N(-1, 0) in 2-d lattice N
>>> from sage.all import * >>> face = square.edges()[Integer(0)] # needs sage.graphs >>> face.interior_points() # needs sage.graphs N(-1, 0) in 2-d lattice N
- is_reflexive()[source]¶
Return
Trueif this polytope is reflexive.EXAMPLES: The 3-dimensional octahedron is reflexive (and 4319 other 3-polytopes):
sage: o = lattice_polytope.cross_polytope(3) sage: o.is_reflexive() True
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.is_reflexive() True
But not all polytopes are reflexive:
sage: p = LatticePolytope([(1,0,0), (0,1,17), (-1,0,0), (0,-1,0)]) sage: p.is_reflexive() False
>>> from sage.all import * >>> p = LatticePolytope([(Integer(1),Integer(0),Integer(0)), (Integer(0),Integer(1),Integer(17)), (-Integer(1),Integer(0),Integer(0)), (Integer(0),-Integer(1),Integer(0))]) >>> p.is_reflexive() False
Only full-dimensional polytopes can be reflexive (otherwise the polar set is not a polytope at all, since it is unbounded):
sage: p = LatticePolytope([(1,0,0), (0,1,0), (-1,0,0), (0,-1,0)]) sage: p.is_reflexive() False
>>> from sage.all import * >>> p = LatticePolytope([(Integer(1),Integer(0),Integer(0)), (Integer(0),Integer(1),Integer(0)), (-Integer(1),Integer(0),Integer(0)), (Integer(0),-Integer(1),Integer(0))]) >>> p.is_reflexive() False
- lattice()[source]¶
Return the ambient lattice of
self.OUTPUT: a lattice
EXAMPLES:
sage: lattice_polytope.cross_polytope(3).lattice() 3-d lattice M
>>> from sage.all import * >>> lattice_polytope.cross_polytope(Integer(3)).lattice() 3-d lattice M
- lattice_dim()[source]¶
Return the dimension of the ambient lattice of
self.An alias is
ambient_dim().OUTPUT: integer
EXAMPLES:
sage: p = LatticePolytope([(1,0)]) sage: p.lattice_dim() 2 sage: p.dim() 0
>>> from sage.all import * >>> p = LatticePolytope([(Integer(1),Integer(0))]) >>> p.lattice_dim() 2 >>> p.dim() 0
- linearly_independent_vertices()[source]¶
Return a maximal set of linearly independent vertices.
OUTPUT: a tuple of vertex indices
EXAMPLES:
sage: L = LatticePolytope([[0, 0], [-1, 1], [-1, -1]]) sage: L.linearly_independent_vertices() (1, 2) sage: L = LatticePolytope([[0, 0, 0]]) sage: L.linearly_independent_vertices() () sage: L = LatticePolytope([[0, 1, 0]]) sage: L.linearly_independent_vertices() (0,)
>>> from sage.all import * >>> L = LatticePolytope([[Integer(0), Integer(0)], [-Integer(1), Integer(1)], [-Integer(1), -Integer(1)]]) >>> L.linearly_independent_vertices() (1, 2) >>> L = LatticePolytope([[Integer(0), Integer(0), Integer(0)]]) >>> L.linearly_independent_vertices() () >>> L = LatticePolytope([[Integer(0), Integer(1), Integer(0)]]) >>> L.linearly_independent_vertices() (0,)
- nef_partitions(keep_symmetric=False, keep_products=True, keep_projections=True, hodge_numbers=False)[source]¶
Return 2-part nef-partitions of
self.INPUT:
keep_symmetric– boolean (default:False); ifTrue, “-s” option will be passed tonef.xin order to keep symmetric partitions, i.e. partitions related by lattice automorphisms preservingselfkeep_products– boolean (default:True); ifTrue, “-D” option will be passed tonef.xin order to keep product partitions, with corresponding complete intersections being direct productskeep_projections– boolean (default:True); ifTrue, “-P” option will be passed tonef.xin order to keep projection partitions, i.e. partitions with one of the parts consisting of a single vertexhodge_numbers– boolean (default:False); ifFalse, “-p” option will be passed tonef.xin order to skip Hodge numbers computation, which takes a lot of time
OUTPUT: a sequence of
nef-partitionsType
NefPartition?for definitions and notation.EXAMPLES:
Nef-partitions of the 4-dimensional cross-polytope:
sage: p = lattice_polytope.cross_polytope(4) sage: p.nef_partitions() # needs palp [ Nef-partition {0, 1, 4, 5} ⊔ {2, 3, 6, 7} (direct product), Nef-partition {0, 1, 2, 4} ⊔ {3, 5, 6, 7}, Nef-partition {0, 1, 2, 4, 5} ⊔ {3, 6, 7}, Nef-partition {0, 1, 2, 4, 5, 6} ⊔ {3, 7} (direct product), Nef-partition {0, 1, 2, 3} ⊔ {4, 5, 6, 7}, Nef-partition {0, 1, 2, 3, 4} ⊔ {5, 6, 7}, Nef-partition {0, 1, 2, 3, 4, 5} ⊔ {6, 7}, Nef-partition {0, 1, 2, 3, 4, 5, 6} ⊔ {7} (projection) ]
>>> from sage.all import * >>> p = lattice_polytope.cross_polytope(Integer(4)) >>> p.nef_partitions() # needs palp [ Nef-partition {0, 1, 4, 5} ⊔ {2, 3, 6, 7} (direct product), Nef-partition {0, 1, 2, 4} ⊔ {3, 5, 6, 7}, Nef-partition {0, 1, 2, 4, 5} ⊔ {3, 6, 7}, Nef-partition {0, 1, 2, 4, 5, 6} ⊔ {3, 7} (direct product), Nef-partition {0, 1, 2, 3} ⊔ {4, 5, 6, 7}, Nef-partition {0, 1, 2, 3, 4} ⊔ {5, 6, 7}, Nef-partition {0, 1, 2, 3, 4, 5} ⊔ {6, 7}, Nef-partition {0, 1, 2, 3, 4, 5, 6} ⊔ {7} (projection) ]
Now we omit projections:
sage: p.nef_partitions(keep_projections=False) # needs palp [ Nef-partition {0, 1, 4, 5} ⊔ {2, 3, 6, 7} (direct product), Nef-partition {0, 1, 2, 4} ⊔ {3, 5, 6, 7}, Nef-partition {0, 1, 2, 4, 5} ⊔ {3, 6, 7}, Nef-partition {0, 1, 2, 4, 5, 6} ⊔ {3, 7} (direct product), Nef-partition {0, 1, 2, 3} ⊔ {4, 5, 6, 7}, Nef-partition {0, 1, 2, 3, 4} ⊔ {5, 6, 7}, Nef-partition {0, 1, 2, 3, 4, 5} ⊔ {6, 7} ]
>>> from sage.all import * >>> p.nef_partitions(keep_projections=False) # needs palp [ Nef-partition {0, 1, 4, 5} ⊔ {2, 3, 6, 7} (direct product), Nef-partition {0, 1, 2, 4} ⊔ {3, 5, 6, 7}, Nef-partition {0, 1, 2, 4, 5} ⊔ {3, 6, 7}, Nef-partition {0, 1, 2, 4, 5, 6} ⊔ {3, 7} (direct product), Nef-partition {0, 1, 2, 3} ⊔ {4, 5, 6, 7}, Nef-partition {0, 1, 2, 3, 4} ⊔ {5, 6, 7}, Nef-partition {0, 1, 2, 3, 4, 5} ⊔ {6, 7} ]
Currently Hodge numbers cannot be computed for a given nef-partition:
sage: p.nef_partitions()[1].hodge_numbers() # needs palp Traceback (most recent call last): ... NotImplementedError: use nef_partitions(hodge_numbers=True)!
>>> from sage.all import * >>> p.nef_partitions()[Integer(1)].hodge_numbers() # needs palp Traceback (most recent call last): ... NotImplementedError: use nef_partitions(hodge_numbers=True)!
But they can be obtained from
nef.xfor all nef-partitions at once. Partitions will be exactly the same:sage: p.nef_partitions(hodge_numbers=True) # long time (2s on sage.math, 2011), needs palp [ Nef-partition {0, 1, 4, 5} ⊔ {2, 3, 6, 7} (direct product), Nef-partition {0, 1, 2, 4} ⊔ {3, 5, 6, 7}, Nef-partition {0, 1, 2, 4, 5} ⊔ {3, 6, 7}, Nef-partition {0, 1, 2, 4, 5, 6} ⊔ {3, 7} (direct product), Nef-partition {0, 1, 2, 3} ⊔ {4, 5, 6, 7}, Nef-partition {0, 1, 2, 3, 4} ⊔ {5, 6, 7}, Nef-partition {0, 1, 2, 3, 4, 5} ⊔ {6, 7}, Nef-partition {0, 1, 2, 3, 4, 5, 6} ⊔ {7} (projection) ]
>>> from sage.all import * >>> p.nef_partitions(hodge_numbers=True) # long time (2s on sage.math, 2011), needs palp [ Nef-partition {0, 1, 4, 5} ⊔ {2, 3, 6, 7} (direct product), Nef-partition {0, 1, 2, 4} ⊔ {3, 5, 6, 7}, Nef-partition {0, 1, 2, 4, 5} ⊔ {3, 6, 7}, Nef-partition {0, 1, 2, 4, 5, 6} ⊔ {3, 7} (direct product), Nef-partition {0, 1, 2, 3} ⊔ {4, 5, 6, 7}, Nef-partition {0, 1, 2, 3, 4} ⊔ {5, 6, 7}, Nef-partition {0, 1, 2, 3, 4, 5} ⊔ {6, 7}, Nef-partition {0, 1, 2, 3, 4, 5, 6} ⊔ {7} (projection) ]
Now it is possible to get Hodge numbers:
sage: p.nef_partitions(hodge_numbers=True)[1].hodge_numbers() # needs palp (20,)
>>> from sage.all import * >>> p.nef_partitions(hodge_numbers=True)[Integer(1)].hodge_numbers() # needs palp (20,)
Since nef-partitions are cached, their Hodge numbers are accessible after the first request, even if you do not specify
hodge_numbers=Trueanymore:sage: p.nef_partitions()[1].hodge_numbers() # needs palp (20,)
>>> from sage.all import * >>> p.nef_partitions()[Integer(1)].hodge_numbers() # needs palp (20,)
We illustrate removal of symmetric partitions on a diamond:
sage: p = lattice_polytope.cross_polytope(2) sage: p.nef_partitions() # needs palp [ Nef-partition {0, 2} ⊔ {1, 3} (direct product), Nef-partition {0, 1} ⊔ {2, 3}, Nef-partition {0, 1, 2} ⊔ {3} (projection) ] sage: p.nef_partitions(keep_symmetric=True) # needs palp [ Nef-partition {0, 1, 3} ⊔ {2} (projection), Nef-partition {0, 2, 3} ⊔ {1} (projection), Nef-partition {0, 3} ⊔ {1, 2}, Nef-partition {1, 2, 3} ⊔ {0} (projection), Nef-partition {1, 3} ⊔ {0, 2} (direct product), Nef-partition {2, 3} ⊔ {0, 1}, Nef-partition {0, 1, 2} ⊔ {3} (projection) ]
>>> from sage.all import * >>> p = lattice_polytope.cross_polytope(Integer(2)) >>> p.nef_partitions() # needs palp [ Nef-partition {0, 2} ⊔ {1, 3} (direct product), Nef-partition {0, 1} ⊔ {2, 3}, Nef-partition {0, 1, 2} ⊔ {3} (projection) ] >>> p.nef_partitions(keep_symmetric=True) # needs palp [ Nef-partition {0, 1, 3} ⊔ {2} (projection), Nef-partition {0, 2, 3} ⊔ {1} (projection), Nef-partition {0, 3} ⊔ {1, 2}, Nef-partition {1, 2, 3} ⊔ {0} (projection), Nef-partition {1, 3} ⊔ {0, 2} (direct product), Nef-partition {2, 3} ⊔ {0, 1}, Nef-partition {0, 1, 2} ⊔ {3} (projection) ]
Nef-partitions can be computed only for reflexive polytopes:
sage: p = LatticePolytope([(1,0,0), (0,1,0), (0,0,2), ....: (-1,0,0), (0,-1,0), (0,0,-1)]) sage: p.nef_partitions() # needs palp Traceback (most recent call last): ... ValueError: The given polytope is not reflexive! Polytope: 3-d lattice polytope in 3-d lattice M
>>> from sage.all import * >>> p = LatticePolytope([(Integer(1),Integer(0),Integer(0)), (Integer(0),Integer(1),Integer(0)), (Integer(0),Integer(0),Integer(2)), ... (-Integer(1),Integer(0),Integer(0)), (Integer(0),-Integer(1),Integer(0)), (Integer(0),Integer(0),-Integer(1))]) >>> p.nef_partitions() # needs palp Traceback (most recent call last): ... ValueError: The given polytope is not reflexive! Polytope: 3-d lattice polytope in 3-d lattice M
- nef_x(keys)[source]¶
Run
nef.xwith givenkeyson vertices of this polytope.INPUT:
keys– string of options passed tonef.x; the key “-f” is added automatically
OUTPUT: the output of
nef.xas a stringEXAMPLES: This call is used internally for computing nef-partitions:
sage: o = lattice_polytope.cross_polytope(3) sage: s = o.nef_x("-N -V -p") # needs palp sage: s # output contains random time # needs palp M:27 8 N:7 6 codim=2 #part=5 3 6 Vertices of P: 1 0 0 -1 0 0 0 1 0 0 -1 0 0 0 1 0 0 -1 P:0 V:2 4 5 0sec 0cpu P:2 V:3 4 5 0sec 0cpu P:3 V:4 5 0sec 0cpu np=3 d:1 p:1 0sec 0cpu
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> s = o.nef_x("-N -V -p") # needs palp >>> s # output contains random time # needs palp M:27 8 N:7 6 codim=2 #part=5 3 6 Vertices of P: 1 0 0 -1 0 0 0 1 0 0 -1 0 0 0 1 0 0 -1 P:0 V:2 4 5 0sec 0cpu P:2 V:3 4 5 0sec 0cpu P:3 V:4 5 0sec 0cpu np=3 d:1 p:1 0sec 0cpu
- nfacets()[source]¶
Return the number of facets of this polytope.
EXAMPLES: The number of facets of the 3-dimensional octahedron:
sage: o = lattice_polytope.cross_polytope(3) sage: o.nfacets() 8
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.nfacets() 8
The number of facets of an interval is 2:
sage: LatticePolytope(([1],[2])).nfacets() 2
>>> from sage.all import * >>> LatticePolytope(([Integer(1)],[Integer(2)])).nfacets() 2
Now consider a 2-dimensional diamond in a 3-dimensional space:
sage: p = LatticePolytope([(1,0,0), (0,1,0), (-1,0,0), (0,-1,0)]) sage: p.nfacets() 4
>>> from sage.all import * >>> p = LatticePolytope([(Integer(1),Integer(0),Integer(0)), (Integer(0),Integer(1),Integer(0)), (-Integer(1),Integer(0),Integer(0)), (Integer(0),-Integer(1),Integer(0))]) >>> p.nfacets() 4
- normal_form(algorithm='palp_native', permutation=False)[source]¶
Return the normal form of vertices of
self.Two full-dimensional lattice polytopes are in the same \(GL(\ZZ^n)\)-orbit if and only if their normal forms are the same. Normal form is not defined and thus cannot be used for polytopes whose dimension is smaller than the dimension of the ambient space.
The original algorithm was presented in [KS1998] and implemented in PALP. A modified version of the PALP algorithm is discussed in [GK2013] and available here as
'palp_modified'.INPUT:
algorithm– (default:'palp_native') the algorithm which is used to compute the normal form. Options are:'palp'– run external PALP code, usually the fastest option when it works; but reproducible crashes have been observed in dimension 5 and higher.'palp_native'– the original PALP algorithm implemented in sage. Currently competitive with PALP in many cases.'palp_modified'– a modified version of the PALP algorithm which determines the maximal vertex-facet pairing matrix first and then computes its automorphisms, while the PALP algorithm does both things concurrently.
permutation– boolean (default:False); ifTrue, the permutation applied to vertices to obtain the normal form is returned as well. Note that the different algorithms may return different results that nevertheless lead to the same normal form.
OUTPUT:
a
point collectionin thelattice()ofselfor a tuple of it and a permutation.
EXAMPLES:
We compute the normal form of the “diamond”:
sage: d = LatticePolytope([(1,0), (0,1), (-1,0), (0,-1)]) sage: d.vertices() M( 1, 0), M( 0, 1), M(-1, 0), M( 0, -1) in 2-d lattice M sage: d.normal_form() # needs sage.groups M( 1, 0), M( 0, 1), M( 0, -1), M(-1, 0) in 2-d lattice M
>>> from sage.all import * >>> d = LatticePolytope([(Integer(1),Integer(0)), (Integer(0),Integer(1)), (-Integer(1),Integer(0)), (Integer(0),-Integer(1))]) >>> d.vertices() M( 1, 0), M( 0, 1), M(-1, 0), M( 0, -1) in 2-d lattice M >>> d.normal_form() # needs sage.groups M( 1, 0), M( 0, 1), M( 0, -1), M(-1, 0) in 2-d lattice M
The diamond is the 3rd polytope in the internal database:
sage: d.index() # needs palp 3 sage: d # needs palp 2-d reflexive polytope #3 in 2-d lattice M
>>> from sage.all import * >>> d.index() # needs palp 3 >>> d # needs palp 2-d reflexive polytope #3 in 2-d lattice M
You can get it in its normal form (in the default lattice) as
sage: lattice_polytope.ReflexivePolytope(2, 3).vertices() M( 1, 0), M( 0, 1), M( 0, -1), M(-1, 0) in 2-d lattice M
>>> from sage.all import * >>> lattice_polytope.ReflexivePolytope(Integer(2), Integer(3)).vertices() M( 1, 0), M( 0, 1), M( 0, -1), M(-1, 0) in 2-d lattice M
It is not possible to compute normal forms for polytopes which do not span the space:
sage: p = LatticePolytope([(1,0,0), (0,1,0), (-1,0,0), (0,-1,0)]) sage: p.normal_form() Traceback (most recent call last): ... ValueError: normal form is not defined for 2-d lattice polytope in 3-d lattice M
>>> from sage.all import * >>> p = LatticePolytope([(Integer(1),Integer(0),Integer(0)), (Integer(0),Integer(1),Integer(0)), (-Integer(1),Integer(0),Integer(0)), (Integer(0),-Integer(1),Integer(0))]) >>> p.normal_form() Traceback (most recent call last): ... ValueError: normal form is not defined for 2-d lattice polytope in 3-d lattice M
We can perform the same examples using other algorithms:
sage: o = lattice_polytope.cross_polytope(2) sage: o.normal_form(algorithm='palp_native') # needs sage.groups M( 1, 0), M( 0, 1), M( 0, -1), M(-1, 0) in 2-d lattice M sage: o = lattice_polytope.cross_polytope(2) sage: o.normal_form(algorithm='palp_modified') # needs sage.groups M( 1, 0), M( 0, 1), M( 0, -1), M(-1, 0) in 2-d lattice M
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(2)) >>> o.normal_form(algorithm='palp_native') # needs sage.groups M( 1, 0), M( 0, 1), M( 0, -1), M(-1, 0) in 2-d lattice M >>> o = lattice_polytope.cross_polytope(Integer(2)) >>> o.normal_form(algorithm='palp_modified') # needs sage.groups M( 1, 0), M( 0, 1), M( 0, -1), M(-1, 0) in 2-d lattice M
The following examples demonstrate the speed of the available algorithms. In low dimensions, the default algorithm,
'palp_native', is the fastest. As the dimension increases,'palp'is relatively faster than'palp_native'.'palp_native'is usually much faster than'palp_modified'. In some cases when the polytope has high symmetry, however,'palp_native'is slower:sage: # not tested sage: o = lattice_polytope.cross_polytope(2) sage: %timeit o.normal_form.clear_cache(); o.normal_form("palp") 625 loops, best of 3: 3.07 ms per loop sage: %timeit o.normal_form.clear_cache(); o.normal_form("palp_native") 625 loops, best of 3: 0.445 ms per loop sage: %timeit o.normal_form.clear_cache(); o.normal_form("palp_modified") 625 loops, best of 3: 5.01 ms per loop sage: o = lattice_polytope.cross_polytope(3) sage: %timeit o.normal_form.clear_cache(); o.normal_form("palp") 625 loops, best of 3: 3.22 ms per loop sage: %timeit o.normal_form.clear_cache(); o.normal_form("palp_native") 625 loops, best of 3: 2.73 ms per loop sage: %timeit o.normal_form.clear_cache(); o.normal_form("palp_modified") 625 loops, best of 3: 20.7 ms per loop sage: o = lattice_polytope.cross_polytope(4) sage: %timeit o.normal_form.clear_cache(); o.normal_form("palp") 625 loops, best of 3: 4.84 ms per loop sage: %timeit o.normal_form.clear_cache(); o.normal_form("palp_native") 625 loops, best of 3: 55.6 ms per loop sage: %timeit o.normal_form.clear_cache(); o.normal_form("palp_modified") 625 loops, best of 3: 129 ms per loop sage: o = lattice_polytope.cross_polytope(5) sage: %timeit o.normal_form.clear_cache(); o.normal_form("palp") 10 loops, best of 3: 0.0364 s per loop sage: %timeit o.normal_form.clear_cache(); o.normal_form("palp_native") 10 loops, best of 3: 1.68 s per loop sage: %timeit o.normal_form.clear_cache(); o.normal_form("palp_modified") 10 loops, best of 3: 0.858 s per loop
>>> from sage.all import * >>> # not tested >>> o = lattice_polytope.cross_polytope(Integer(2)) >>> %timeit o.normal_form.clear_cache(); o.normal_form("palp") 625 loops, best of 3: 3.07 ms per loop >>> %timeit o.normal_form.clear_cache(); o.normal_form("palp_native") 625 loops, best of 3: 0.445 ms per loop >>> %timeit o.normal_form.clear_cache(); o.normal_form("palp_modified") 625 loops, best of 3: 5.01 ms per loop >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> %timeit o.normal_form.clear_cache(); o.normal_form("palp") 625 loops, best of 3: 3.22 ms per loop >>> %timeit o.normal_form.clear_cache(); o.normal_form("palp_native") 625 loops, best of 3: 2.73 ms per loop >>> %timeit o.normal_form.clear_cache(); o.normal_form("palp_modified") 625 loops, best of 3: 20.7 ms per loop >>> o = lattice_polytope.cross_polytope(Integer(4)) >>> %timeit o.normal_form.clear_cache(); o.normal_form("palp") 625 loops, best of 3: 4.84 ms per loop >>> %timeit o.normal_form.clear_cache(); o.normal_form("palp_native") 625 loops, best of 3: 55.6 ms per loop >>> %timeit o.normal_form.clear_cache(); o.normal_form("palp_modified") 625 loops, best of 3: 129 ms per loop >>> o = lattice_polytope.cross_polytope(Integer(5)) >>> %timeit o.normal_form.clear_cache(); o.normal_form("palp") 10 loops, best of 3: 0.0364 s per loop >>> %timeit o.normal_form.clear_cache(); o.normal_form("palp_native") 10 loops, best of 3: 1.68 s per loop >>> %timeit o.normal_form.clear_cache(); o.normal_form("palp_modified") 10 loops, best of 3: 0.858 s per loop
Note that the algorithm
'palp'may crash for higher dimensions because of the overflow errors as mentioned in Issue #13525#comment:9. Then use'palp_native'instead, which is usually faster than'palp_modified'. Below is an example where'palp'fails and'palp_native'is much faster than'palp_modified':sage: P = LatticePolytope([[-3, -3, -6, -6, -1], [3, 3, 6, 6, 1], [-3, -3, -6, -6, 1], ....: [-3, -3, -3, -6, 0], [-3, -3, -3, 0, 0], [-3, -3, 0, 0, 0], ....: [-3, 0, -6, -6, 0], [-3, 0, -3, -6, 0], [-3, 0, -3, 0, 0], ....: [-3, 0, 0, 0, -1], [3, 3, 6, 6, -1], [-3, 0, 0, 0, 1], ....: [0, -3, -6, -6, 0], [0, -3, -3, -6, 0], [0, -3, -3, 0, 0], ....: [0, -3, 0, 0, -1], [3, 3, 3, 6, 0], [0, -3, 0, 0, 1], ....: [0, 0, -6, -6, 0], [0, 0, -3, -6, -1], [3, 3, 3, 0, 0], ....: [0, 0, -3, -6, 1], [0, 0, -3, 0, -1], [3, 3, 0, 0, 0], ....: [0, 0, -3, 0, 1], [0, 0, 3, 0, -1], [3, 0, 6, 6, 0], ....: [0, 0, 3, 0, 1], [0, 0, 3, 6, -1], [3, 0, 3, 6, 0], ....: [0, 0, 3, 6, 1], [0, 0, 6, 6, 0], [0, 3, 0, 0, -1], ....: [3, 0, 3, 0, 0], [0, 3, 0, 0, 1], [0, 3, 3, 0, 0], ....: [0, 3, 3, 6, 0], [0, 3, 6, 6, 0], [3, 0,0, 0, -1], [3, 0, 0, 0, 1]]) sage: P.normal_form(algorithm='palp') # not tested Traceback (most recent call last): ... RuntimeError: Error executing ... for a polytope sequence! Output: b'*** stack smashing detected ***: terminated\nAborted\n' sage: P.normal_form(algorithm='palp_native') # needs sage.groups M( 6, 0, 0, 0, 0), M( -6, 0, 0, 0, 0), M( 0, 1, 0, 0, 0), M( 0, 0, 3, 0, 0), M( 0, 1, 0, 3, 0), M( 0, 0, 0, 0, 3), M( -6, 1, 6, 3, -6), M( -6, 0, 6, 0, -3), M(-12, 1, 6, 3, -3), M( -6, 1, 0, 3, 0), M( -6, 0, 3, 3, 0), M( 6, 0, -6, -3, 6), M(-12, 1, 6, 3, -6), M(-12, 0, 9, 3, -6), M( 0, 0, 0, -3, 0), M(-12, 1, 6, 6, -6), M(-12, 0, 6, 3, -3), M( 0, 1, -3, 0, 0), M( 0, 0, -3, -3, 3), M( 0, 1, 0, 3, -3), M( 0, -1, 0, -3, 3), M( 0, 0, 3, 3, -3), M( 0, -1, 3, 0, 0), M( 12, 0, -6, -3, 3), M( 12, -1, -6, -6, 6), M( 0, 0, 0, 3, 0), M( 12, 0, -9, -3, 6), M( 12, -1, -6, -3, 6), M( -6, 0, 6, 3, -6), M( 6, 0, -3, -3, 0), M( 6, -1, 0, -3, 0), M(-12, 1, 9, 6, -6), M( 6, 0, -6, 0, 3), M( 6, -1, -6, -3, 6), M( 0, 0, 0, 0, -3), M( 0, -1, 0, -3, 0), M( 0, 0, -3, 0, 0), M( 0, -1, 0, 0, 0), M( 12, -1, -9, -6, 6), M( 12, -1, -6, -3, 3) in 5-d lattice M sage: P.normal_form(algorithm='palp_modified') # not tested (22s; MemoryError on 32 bit), needs sage.groups M( 6, 0, 0, 0, 0), M( -6, 0, 0, 0, 0), M( 0, 1, 0, 0, 0), M( 0, 0, 3, 0, 0), M( 0, 1, 0, 3, 0), M( 0, 0, 0, 0, 3), M( -6, 1, 6, 3, -6), M( -6, 0, 6, 0, -3), M(-12, 1, 6, 3, -3), M( -6, 1, 0, 3, 0), M( -6, 0, 3, 3, 0), M( 6, 0, -6, -3, 6), M(-12, 1, 6, 3, -6), M(-12, 0, 9, 3, -6), M( 0, 0, 0, -3, 0), M(-12, 1, 6, 6, -6), M(-12, 0, 6, 3, -3), M( 0, 1, -3, 0, 0), M( 0, 0, -3, -3, 3), M( 0, 1, 0, 3, -3), M( 0, -1, 0, -3, 3), M( 0, 0, 3, 3, -3), M( 0, -1, 3, 0, 0), M( 12, 0, -6, -3, 3), M( 12, -1, -6, -6, 6), M( 0, 0, 0, 3, 0), M( 12, 0, -9, -3, 6), M( 12, -1, -6, -3, 6), M( -6, 0, 6, 3, -6), M( 6, 0, -3, -3, 0), M( 6, -1, 0, -3, 0), M(-12, 1, 9, 6, -6), M( 6, 0, -6, 0, 3), M( 6, -1, -6, -3, 6), M( 0, 0, 0, 0, -3), M( 0, -1, 0, -3, 0), M( 0, 0, -3, 0, 0), M( 0, -1, 0, 0, 0), M( 12, -1, -9, -6, 6), M( 12, -1, -6, -3, 3) in 5-d lattice M sage: %timeit P.normal_form.clear_cache(); P.normal_form("palp_native") # not tested 10 loops, best of 3: 0.137 s per loop sage: %timeit P.normal_form.clear_cache(); P.normal_form("palp_modified") # not tested 10 loops, best of 3: 22.2 s per loop
>>> from sage.all import * >>> P = LatticePolytope([[-Integer(3), -Integer(3), -Integer(6), -Integer(6), -Integer(1)], [Integer(3), Integer(3), Integer(6), Integer(6), Integer(1)], [-Integer(3), -Integer(3), -Integer(6), -Integer(6), Integer(1)], ... [-Integer(3), -Integer(3), -Integer(3), -Integer(6), Integer(0)], [-Integer(3), -Integer(3), -Integer(3), Integer(0), Integer(0)], [-Integer(3), -Integer(3), Integer(0), Integer(0), Integer(0)], ... [-Integer(3), Integer(0), -Integer(6), -Integer(6), Integer(0)], [-Integer(3), Integer(0), -Integer(3), -Integer(6), Integer(0)], [-Integer(3), Integer(0), -Integer(3), Integer(0), Integer(0)], ... [-Integer(3), Integer(0), Integer(0), Integer(0), -Integer(1)], [Integer(3), Integer(3), Integer(6), Integer(6), -Integer(1)], [-Integer(3), Integer(0), Integer(0), Integer(0), Integer(1)], ... [Integer(0), -Integer(3), -Integer(6), -Integer(6), Integer(0)], [Integer(0), -Integer(3), -Integer(3), -Integer(6), Integer(0)], [Integer(0), -Integer(3), -Integer(3), Integer(0), Integer(0)], ... [Integer(0), -Integer(3), Integer(0), Integer(0), -Integer(1)], [Integer(3), Integer(3), Integer(3), Integer(6), Integer(0)], [Integer(0), -Integer(3), Integer(0), Integer(0), Integer(1)], ... [Integer(0), Integer(0), -Integer(6), -Integer(6), Integer(0)], [Integer(0), Integer(0), -Integer(3), -Integer(6), -Integer(1)], [Integer(3), Integer(3), Integer(3), Integer(0), Integer(0)], ... [Integer(0), Integer(0), -Integer(3), -Integer(6), Integer(1)], [Integer(0), Integer(0), -Integer(3), Integer(0), -Integer(1)], [Integer(3), Integer(3), Integer(0), Integer(0), Integer(0)], ... [Integer(0), Integer(0), -Integer(3), Integer(0), Integer(1)], [Integer(0), Integer(0), Integer(3), Integer(0), -Integer(1)], [Integer(3), Integer(0), Integer(6), Integer(6), Integer(0)], ... [Integer(0), Integer(0), Integer(3), Integer(0), Integer(1)], [Integer(0), Integer(0), Integer(3), Integer(6), -Integer(1)], [Integer(3), Integer(0), Integer(3), Integer(6), Integer(0)], ... [Integer(0), Integer(0), Integer(3), Integer(6), Integer(1)], [Integer(0), Integer(0), Integer(6), Integer(6), Integer(0)], [Integer(0), Integer(3), Integer(0), Integer(0), -Integer(1)], ... [Integer(3), Integer(0), Integer(3), Integer(0), Integer(0)], [Integer(0), Integer(3), Integer(0), Integer(0), Integer(1)], [Integer(0), Integer(3), Integer(3), Integer(0), Integer(0)], ... [Integer(0), Integer(3), Integer(3), Integer(6), Integer(0)], [Integer(0), Integer(3), Integer(6), Integer(6), Integer(0)], [Integer(3), Integer(0),Integer(0), Integer(0), -Integer(1)], [Integer(3), Integer(0), Integer(0), Integer(0), Integer(1)]]) >>> P.normal_form(algorithm='palp') # not tested Traceback (most recent call last): ... RuntimeError: Error executing ... for a polytope sequence! Output: b'*** stack smashing detected ***: terminated\nAborted\n' >>> P.normal_form(algorithm='palp_native') # needs sage.groups M( 6, 0, 0, 0, 0), M( -6, 0, 0, 0, 0), M( 0, 1, 0, 0, 0), M( 0, 0, 3, 0, 0), M( 0, 1, 0, 3, 0), M( 0, 0, 0, 0, 3), M( -6, 1, 6, 3, -6), M( -6, 0, 6, 0, -3), M(-12, 1, 6, 3, -3), M( -6, 1, 0, 3, 0), M( -6, 0, 3, 3, 0), M( 6, 0, -6, -3, 6), M(-12, 1, 6, 3, -6), M(-12, 0, 9, 3, -6), M( 0, 0, 0, -3, 0), M(-12, 1, 6, 6, -6), M(-12, 0, 6, 3, -3), M( 0, 1, -3, 0, 0), M( 0, 0, -3, -3, 3), M( 0, 1, 0, 3, -3), M( 0, -1, 0, -3, 3), M( 0, 0, 3, 3, -3), M( 0, -1, 3, 0, 0), M( 12, 0, -6, -3, 3), M( 12, -1, -6, -6, 6), M( 0, 0, 0, 3, 0), M( 12, 0, -9, -3, 6), M( 12, -1, -6, -3, 6), M( -6, 0, 6, 3, -6), M( 6, 0, -3, -3, 0), M( 6, -1, 0, -3, 0), M(-12, 1, 9, 6, -6), M( 6, 0, -6, 0, 3), M( 6, -1, -6, -3, 6), M( 0, 0, 0, 0, -3), M( 0, -1, 0, -3, 0), M( 0, 0, -3, 0, 0), M( 0, -1, 0, 0, 0), M( 12, -1, -9, -6, 6), M( 12, -1, -6, -3, 3) in 5-d lattice M >>> P.normal_form(algorithm='palp_modified') # not tested (22s; MemoryError on 32 bit), needs sage.groups M( 6, 0, 0, 0, 0), M( -6, 0, 0, 0, 0), M( 0, 1, 0, 0, 0), M( 0, 0, 3, 0, 0), M( 0, 1, 0, 3, 0), M( 0, 0, 0, 0, 3), M( -6, 1, 6, 3, -6), M( -6, 0, 6, 0, -3), M(-12, 1, 6, 3, -3), M( -6, 1, 0, 3, 0), M( -6, 0, 3, 3, 0), M( 6, 0, -6, -3, 6), M(-12, 1, 6, 3, -6), M(-12, 0, 9, 3, -6), M( 0, 0, 0, -3, 0), M(-12, 1, 6, 6, -6), M(-12, 0, 6, 3, -3), M( 0, 1, -3, 0, 0), M( 0, 0, -3, -3, 3), M( 0, 1, 0, 3, -3), M( 0, -1, 0, -3, 3), M( 0, 0, 3, 3, -3), M( 0, -1, 3, 0, 0), M( 12, 0, -6, -3, 3), M( 12, -1, -6, -6, 6), M( 0, 0, 0, 3, 0), M( 12, 0, -9, -3, 6), M( 12, -1, -6, -3, 6), M( -6, 0, 6, 3, -6), M( 6, 0, -3, -3, 0), M( 6, -1, 0, -3, 0), M(-12, 1, 9, 6, -6), M( 6, 0, -6, 0, 3), M( 6, -1, -6, -3, 6), M( 0, 0, 0, 0, -3), M( 0, -1, 0, -3, 0), M( 0, 0, -3, 0, 0), M( 0, -1, 0, 0, 0), M( 12, -1, -9, -6, 6), M( 12, -1, -6, -3, 3) in 5-d lattice M >>> %timeit P.normal_form.clear_cache(); P.normal_form("palp_native") # not tested 10 loops, best of 3: 0.137 s per loop >>> %timeit P.normal_form.clear_cache(); P.normal_form("palp_modified") # not tested 10 loops, best of 3: 22.2 s per loop
- npoints()[source]¶
Return the number of lattice points of this polytope.
EXAMPLES: The number of lattice points of the 3-dimensional octahedron and its polar cube:
sage: o = lattice_polytope.cross_polytope(3) sage: o.npoints() # needs palp 7 sage: cube = o.polar() sage: cube.npoints() # needs palp 27
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.npoints() # needs palp 7 >>> cube = o.polar() >>> cube.npoints() # needs palp 27
- nvertices()[source]¶
Return the number of vertices of this polytope.
EXAMPLES: The number of vertices of the 3-dimensional octahedron and its polar cube:
sage: o = lattice_polytope.cross_polytope(3) sage: o.nvertices() 6 sage: cube = o.polar() sage: cube.nvertices() 8
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.nvertices() 6 >>> cube = o.polar() >>> cube.nvertices() 8
- origin()[source]¶
Return the index of the origin in the list of points of
self.OUTPUT: integer if the origin belongs to this polytope,
NoneotherwiseEXAMPLES:
sage: p = lattice_polytope.cross_polytope(2) sage: p.origin() # needs palp 4 sage: p.point(p.origin()) # needs palp M(0, 0) sage: p = LatticePolytope(([1],[2])) sage: p.points() M(1), M(2) in 1-d lattice M sage: print(p.origin()) None
>>> from sage.all import * >>> p = lattice_polytope.cross_polytope(Integer(2)) >>> p.origin() # needs palp 4 >>> p.point(p.origin()) # needs palp M(0, 0) >>> p = LatticePolytope(([Integer(1)],[Integer(2)])) >>> p.points() M(1), M(2) in 1-d lattice M >>> print(p.origin()) None
Now we make sure that the origin of non-full-dimensional polytopes can be identified correctly (Issue #10661):
sage: LatticePolytope([(1,0,0), (-1,0,0)]).origin() 2
>>> from sage.all import * >>> LatticePolytope([(Integer(1),Integer(0),Integer(0)), (-Integer(1),Integer(0),Integer(0))]).origin() 2
- parent()[source]¶
Return the set of all lattice polytopes.
EXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: o.parent() Set of all Lattice Polytopes
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.parent() Set of all Lattice Polytopes
- plot3d(show_facets=True, facet_opacity=0.5, facet_color=(0, 1, 0), facet_colors=None, show_edges=True, edge_thickness=3, edge_color=(0.5, 0.5, 0.5), show_vertices=True, vertex_size=10, vertex_color=(1, 0, 0), show_points=True, point_size=10, point_color=(0, 0, 1), show_vindices=None, vindex_color=(0, 0, 0), vlabels=None, show_pindices=None, pindex_color=(0, 0, 0), index_shift=1.1)[source]¶
Return a 3d-plot of this polytope.
Polytopes with ambient dimension 1 and 2 will be plotted along x-axis or in xy-plane respectively. Polytopes of dimension 3 and less with ambient dimension 4 and greater will be plotted in some basis of the spanned space.
By default, everything is shown with more or less pretty combination of size and color parameters.
INPUT:
Most of the parameters are self-explanatory:
show_facets– (default:True)facet_opacity– (default:0.5)facet_color– (default:(0,1,0))facet_colors– (default:None) if specified, must be a list of colors for each facet separately, used instead offacet_colorshow_edges– boolean (default:True); whether to draw edges as linesedge_thickness– (default:3)edge_color– (default:(0.5,0.5,0.5))show_vertices– boolean (default:True); whether to draw vertices as ballsvertex_size– (default:10)vertex_color– (default:(1,0,0))show_points– boolean (default:True); whether to draw other points as ballspoint_size– (default:10)point_color– (default:(0,0,1))show_vindices– (default: same asshow_vertices) whether to show indices of verticesvindex_color– (default:(0,0,0)) color for vertex labelsvlabels– (default:None) if specified, must be a list of labels for each vertex, default labels are vertex indicesshow_pindices– (default: same asshow_points) whether to show indices of other pointspindex_color– (default:(0,0,0)) color for point labelsindex_shift– (default:1.1)) if 1, labels are placed exactly at the corresponding points. Otherwise the label position is computed as a multiple of the point position vector.
EXAMPLES: The default plot of a cube:
sage: c = lattice_polytope.cross_polytope(3).polar() sage: c.plot3d() # needs palp sage.plot Graphics3d Object
>>> from sage.all import * >>> c = lattice_polytope.cross_polytope(Integer(3)).polar() >>> c.plot3d() # needs palp sage.plot Graphics3d Object
Plot without facets and points, shown without the frame:
sage: c.plot3d(show_facets=false, # needs palp sage.plot ....: show_points=false).show(frame=False)
>>> from sage.all import * >>> c.plot3d(show_facets=false, # needs palp sage.plot ... show_points=false).show(frame=False)
Plot with facets of different colors:
sage: c.plot3d(facet_colors=rainbow(c.nfacets(), 'rgbtuple')) # needs palp sage.plot Graphics3d Object
>>> from sage.all import * >>> c.plot3d(facet_colors=rainbow(c.nfacets(), 'rgbtuple')) # needs palp sage.plot Graphics3d Object
It is also possible to plot lower dimensional polytops in 3D (let’s also change labels of vertices):
sage: c2 = lattice_polytope.cross_polytope(2) sage: c2.plot3d(vlabels=["A", "B", "C", "D"]) # needs palp sage.plot Graphics3d Object
>>> from sage.all import * >>> c2 = lattice_polytope.cross_polytope(Integer(2)) >>> c2.plot3d(vlabels=["A", "B", "C", "D"]) # needs palp sage.plot Graphics3d Object
- point(i)[source]¶
Return the \(i\)-th point of this polytope, i.e. the \(i\)-th column of the matrix returned by
points().EXAMPLES: First few points are actually vertices:
sage: o = lattice_polytope.cross_polytope(3) sage: o.vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M sage: o.point(1) # needs palp M(0, 1, 0)
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M >>> o.point(Integer(1)) # needs palp M(0, 1, 0)
The only other point in the octahedron is the origin:
sage: o.point(6) # needs palp M(0, 0, 0) sage: o.points() # needs palp M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1), M( 0, 0, 0) in 3-d lattice M
>>> from sage.all import * >>> o.point(Integer(6)) # needs palp M(0, 0, 0) >>> o.points() # needs palp M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1), M( 0, 0, 0) in 3-d lattice M
- points(*args, **kwds)[source]¶
Return all lattice points of
self.INPUT:
any arguments given will be passed on to the returned object.
OUTPUT: a
point collectionEXAMPLES:
Lattice points of the octahedron and its polar cube:
sage: o = lattice_polytope.cross_polytope(3) sage: o.points() # needs palp M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1), M( 0, 0, 0) in 3-d lattice M sage: cube = o.polar() sage: cube.points() # needs palp N( 1, -1, -1), N( 1, 1, -1), N( 1, 1, 1), N( 1, -1, 1), N(-1, -1, 1), N(-1, -1, -1), N(-1, 1, -1), N(-1, 1, 1), N(-1, -1, 0), N(-1, 0, -1), N(-1, 0, 0), N(-1, 0, 1), N(-1, 1, 0), N( 0, -1, -1), N( 0, -1, 0), N( 0, -1, 1), N( 0, 0, -1), N( 0, 0, 0), N( 0, 0, 1), N( 0, 1, -1), N( 0, 1, 0), N( 0, 1, 1), N( 1, -1, 0), N( 1, 0, -1), N( 1, 0, 0), N( 1, 0, 1), N( 1, 1, 0) in 3-d lattice N
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.points() # needs palp M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1), M( 0, 0, 0) in 3-d lattice M >>> cube = o.polar() >>> cube.points() # needs palp N( 1, -1, -1), N( 1, 1, -1), N( 1, 1, 1), N( 1, -1, 1), N(-1, -1, 1), N(-1, -1, -1), N(-1, 1, -1), N(-1, 1, 1), N(-1, -1, 0), N(-1, 0, -1), N(-1, 0, 0), N(-1, 0, 1), N(-1, 1, 0), N( 0, -1, -1), N( 0, -1, 0), N( 0, -1, 1), N( 0, 0, -1), N( 0, 0, 0), N( 0, 0, 1), N( 0, 1, -1), N( 0, 1, 0), N( 0, 1, 1), N( 1, -1, 0), N( 1, 0, -1), N( 1, 0, 0), N( 1, 0, 1), N( 1, 1, 0) in 3-d lattice N
Lattice points of a 2-dimensional diamond in a 3-dimensional space:
sage: p = LatticePolytope([(1,0,0), (0,1,0), (-1,0,0), (0,-1,0)]) sage: p.points() # needs palp M( 1, 0, 0), M( 0, 1, 0), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, 0) in 3-d lattice M
>>> from sage.all import * >>> p = LatticePolytope([(Integer(1),Integer(0),Integer(0)), (Integer(0),Integer(1),Integer(0)), (-Integer(1),Integer(0),Integer(0)), (Integer(0),-Integer(1),Integer(0))]) >>> p.points() # needs palp M( 1, 0, 0), M( 0, 1, 0), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, 0) in 3-d lattice M
Only two of the above points:
sage: p.points(1, 3) # needs palp M(0, 1, 0), M(0, -1, 0) in 3-d lattice M
>>> from sage.all import * >>> p.points(Integer(1), Integer(3)) # needs palp M(0, 1, 0), M(0, -1, 0) in 3-d lattice M
We check that points of a zero-dimensional polytope can be computed:
sage: p = LatticePolytope([[1]]) sage: p.points() M(1) in 1-d lattice M
>>> from sage.all import * >>> p = LatticePolytope([[Integer(1)]]) >>> p.points() M(1) in 1-d lattice M
- polar()[source]¶
Return the polar polytope, if this polytope is reflexive.
EXAMPLES: The polar polytope to the 3-dimensional octahedron:
sage: o = lattice_polytope.cross_polytope(3) sage: cube = o.polar() sage: cube 3-d reflexive polytope in 3-d lattice N
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> cube = o.polar() >>> cube 3-d reflexive polytope in 3-d lattice N
The polar polytope “remembers” the original one:
sage: cube.polar() 3-d reflexive polytope in 3-d lattice M sage: cube.polar().polar() is cube True
>>> from sage.all import * >>> cube.polar() 3-d reflexive polytope in 3-d lattice M >>> cube.polar().polar() is cube True
Only reflexive polytopes have polars:
sage: p = LatticePolytope([(1,0,0), (0,1,0), (0,0,2), ....: (-1,0,0), (0,-1,0), (0,0,-1)]) sage: p.polar() Traceback (most recent call last): ... ValueError: The given polytope is not reflexive! Polytope: 3-d lattice polytope in 3-d lattice M
>>> from sage.all import * >>> p = LatticePolytope([(Integer(1),Integer(0),Integer(0)), (Integer(0),Integer(1),Integer(0)), (Integer(0),Integer(0),Integer(2)), ... (-Integer(1),Integer(0),Integer(0)), (Integer(0),-Integer(1),Integer(0)), (Integer(0),Integer(0),-Integer(1))]) >>> p.polar() Traceback (most recent call last): ... ValueError: The given polytope is not reflexive! Polytope: 3-d lattice polytope in 3-d lattice M
- poly_x(keys, reduce_dimension=False)[source]¶
Run
poly.xwith givenkeyson vertices of this polytope.INPUT:
keys– string of options passed topoly.x. The key “f” is added automaticallyreduce_dimension– boolean (default:False); ifTrueand this polytope is not full-dimensional,poly.xwill be called for the vertices of this polytope in some basis of the spanned affine space
OUTPUT: the output of
poly.xas a stringEXAMPLES: This call is used for determining if a polytope is reflexive or not:
sage: o = lattice_polytope.cross_polytope(3) sage: print(o.poly_x("e")) # needs palp 8 3 Vertices of P-dual <-> Equations of P -1 -1 1 1 -1 1 -1 1 1 1 1 1 -1 -1 -1 1 -1 -1 -1 1 -1 1 1 -1
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> print(o.poly_x("e")) # needs palp 8 3 Vertices of P-dual <-> Equations of P -1 -1 1 1 -1 1 -1 1 1 1 1 1 -1 -1 -1 1 -1 -1 -1 1 -1 1 1 -1
Since PALP has limits on different parameters determined during compilation, the following code is likely to fail, unless you change default settings of PALP:
sage: BIG = lattice_polytope.cross_polytope(7) sage: BIG 7-d reflexive polytope in 7-d lattice M sage: BIG.poly_x("e") # needs palp Traceback (most recent call last): ... ValueError: Error executing 'poly.x -fe' for the given polytope! Output: Please increase POLY_Dmax to at least 7
>>> from sage.all import * >>> BIG = lattice_polytope.cross_polytope(Integer(7)) >>> BIG 7-d reflexive polytope in 7-d lattice M >>> BIG.poly_x("e") # needs palp Traceback (most recent call last): ... ValueError: Error executing 'poly.x -fe' for the given polytope! Output: Please increase POLY_Dmax to at least 7
You cannot call
poly.xfor polytopes that don’t span the space (if you could, it would crush anyway):sage: p = LatticePolytope([(1,0,0), (0,1,0), (-1,0,0), (0,-1,0)]) sage: p.poly_x("e") # needs palp Traceback (most recent call last): ... ValueError: Cannot run PALP for a 2-dimensional polytope in a 3-dimensional space!
>>> from sage.all import * >>> p = LatticePolytope([(Integer(1),Integer(0),Integer(0)), (Integer(0),Integer(1),Integer(0)), (-Integer(1),Integer(0),Integer(0)), (Integer(0),-Integer(1),Integer(0))]) >>> p.poly_x("e") # needs palp Traceback (most recent call last): ... ValueError: Cannot run PALP for a 2-dimensional polytope in a 3-dimensional space!
But if you know what you are doing, you can call it for the polytope in some basis of the spanned space:
sage: print(p.poly_x("e", reduce_dimension=True)) # needs palp 4 2 Equations of P -1 1 0 1 1 2 -1 -1 0 1 -1 2
>>> from sage.all import * >>> print(p.poly_x("e", reduce_dimension=True)) # needs palp 4 2 Equations of P -1 1 0 1 1 2 -1 -1 0 1 -1 2
- polyhedron(**kwds)[source]¶
Return the Polyhedron object determined by this polytope’s vertices.
EXAMPLES:
sage: o = lattice_polytope.cross_polytope(2) sage: o.polyhedron() A 2-dimensional polyhedron in ZZ^2 defined as the convex hull of 4 vertices
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(2)) >>> o.polyhedron() A 2-dimensional polyhedron in ZZ^2 defined as the convex hull of 4 vertices
- show3d()[source]¶
Show a 3d picture of the polytope with default settings and without axes or frame.
See self.plot3d? for more details.
EXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: o.show3d() # needs palp sage.plot
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.show3d() # needs palp sage.plot
- skeleton()[source]¶
Return the graph of the one-skeleton of this polytope.
EXAMPLES:
sage: d = lattice_polytope.cross_polytope(2) sage: g = d.skeleton(); g # needs palp sage.graphs Graph on 4 vertices sage: g.edges(sort=True) # needs palp sage.graphs [(0, 1, None), (0, 3, None), (1, 2, None), (2, 3, None)]
>>> from sage.all import * >>> d = lattice_polytope.cross_polytope(Integer(2)) >>> g = d.skeleton(); g # needs palp sage.graphs Graph on 4 vertices >>> g.edges(sort=True) # needs palp sage.graphs [(0, 1, None), (0, 3, None), (1, 2, None), (2, 3, None)]
- skeleton_points(k=1)[source]¶
Return the increasing list of indices of lattice points in k-skeleton of the polytope (k is 1 by default).
EXAMPLES: We compute all skeleton points for the cube:
sage: o = lattice_polytope.cross_polytope(3) sage: c = o.polar() sage: c.skeleton_points() # needs palp sage.graphs [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 15, 19, 21, 22, 23, 25, 26]
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> c = o.polar() >>> c.skeleton_points() # needs palp sage.graphs [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 15, 19, 21, 22, 23, 25, 26]
The default was 1-skeleton:
sage: c.skeleton_points(k=1) # needs palp sage.graphs [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 15, 19, 21, 22, 23, 25, 26]
>>> from sage.all import * >>> c.skeleton_points(k=Integer(1)) # needs palp sage.graphs [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 15, 19, 21, 22, 23, 25, 26]
0-skeleton just lists all vertices:
sage: c.skeleton_points(k=0) # needs palp sage.graphs [0, 1, 2, 3, 4, 5, 6, 7]
>>> from sage.all import * >>> c.skeleton_points(k=Integer(0)) # needs palp sage.graphs [0, 1, 2, 3, 4, 5, 6, 7]
2-skeleton lists all points except for the origin (point #17):
sage: c.skeleton_points(k=2) # needs palp sage.graphs [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 18, 19, 20, 21, 22, 23, 24, 25, 26]
>>> from sage.all import * >>> c.skeleton_points(k=Integer(2)) # needs palp sage.graphs [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 18, 19, 20, 21, 22, 23, 24, 25, 26]
3-skeleton includes all points:
sage: c.skeleton_points(k=3) # needs palp [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26]
>>> from sage.all import * >>> c.skeleton_points(k=Integer(3)) # needs palp [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26]
It is OK to compute higher dimensional skeletons - you will get the list of all points:
sage: c.skeleton_points(k=100) # needs palp [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26]
>>> from sage.all import * >>> c.skeleton_points(k=Integer(100)) # needs palp [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26]
- skeleton_show(normal=None)[source]¶
Show the graph of one-skeleton of this polytope. Works only for polytopes in a 3-dimensional space.
INPUT:
normal– a 3-dimensional vector (can be given as a list), which should be perpendicular to the screen. If not given, will be selected randomly (new each time and it may be far from “nice”).
EXAMPLES: Show a pretty picture of the octahedron:
sage: o = lattice_polytope.cross_polytope(3) sage: o.skeleton_show([1,2,4]) # needs palp sage.plot
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.skeleton_show([Integer(1),Integer(2),Integer(4)]) # needs palp sage.plot
Does not work for a diamond at the moment:
sage: d = lattice_polytope.cross_polytope(2) sage: d.skeleton_show() Traceback (most recent call last): ... NotImplementedError: skeleton view is implemented only in 3-d space
>>> from sage.all import * >>> d = lattice_polytope.cross_polytope(Integer(2)) >>> d.skeleton_show() Traceback (most recent call last): ... NotImplementedError: skeleton view is implemented only in 3-d space
- traverse_boundary()[source]¶
Return a list of indices of vertices of a 2-dimensional polytope in their boundary order.
Needed for plot3d function of polytopes.
EXAMPLES:
sage: p = lattice_polytope.cross_polytope(2).polar() sage: p.traverse_boundary() # needs sage.graphs [3, 0, 1, 2]
>>> from sage.all import * >>> p = lattice_polytope.cross_polytope(Integer(2)).polar() >>> p.traverse_boundary() # needs sage.graphs [3, 0, 1, 2]
- vertex(i)[source]¶
Return the \(i\)-th vertex of this polytope, i.e. the \(i\)-th column of the matrix returned by
vertices().EXAMPLES: Note that numeration starts with zero:
sage: o = lattice_polytope.cross_polytope(3) sage: o.vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M sage: o.vertex(3) M(-1, 0, 0)
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M >>> o.vertex(Integer(3)) M(-1, 0, 0)
- vertex_facet_pairing_matrix()[source]¶
Return the vertex facet pairing matrix \(PM\).
Return a matrix whose the \(i, j^\text{th}\) entry is the height of the \(j^\text{th}\) vertex over the \(i^\text{th}\) facet. The ordering of the vertices and facets is as in
vertices()andfacets().EXAMPLES:
sage: L = lattice_polytope.cross_polytope(3) sage: L.vertex_facet_pairing_matrix() [2 0 0 0 2 2] [2 2 0 0 0 2] [2 2 2 0 0 0] [2 0 2 0 2 0] [0 0 2 2 2 0] [0 0 0 2 2 2] [0 2 0 2 0 2] [0 2 2 2 0 0]
>>> from sage.all import * >>> L = lattice_polytope.cross_polytope(Integer(3)) >>> L.vertex_facet_pairing_matrix() [2 0 0 0 2 2] [2 2 0 0 0 2] [2 2 2 0 0 0] [2 0 2 0 2 0] [0 0 2 2 2 0] [0 0 0 2 2 2] [0 2 0 2 0 2] [0 2 2 2 0 0]
- vertices(*args, **kwds)[source]¶
Return vertices of
self.INPUT:
any arguments given will be passed on to the returned object.
OUTPUT: a
point collectionEXAMPLES:
Vertices of the octahedron and its polar cube are in dual lattices:
sage: o = lattice_polytope.cross_polytope(3) sage: o.vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M sage: cube = o.polar() sage: cube.vertices() N( 1, -1, -1), N( 1, 1, -1), N( 1, 1, 1), N( 1, -1, 1), N(-1, -1, 1), N(-1, -1, -1), N(-1, 1, -1), N(-1, 1, 1) in 3-d lattice N
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o.vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M >>> cube = o.polar() >>> cube.vertices() N( 1, -1, -1), N( 1, 1, -1), N( 1, 1, 1), N( 1, -1, 1), N(-1, -1, 1), N(-1, -1, -1), N(-1, 1, -1), N(-1, 1, 1) in 3-d lattice N
- class sage.geometry.lattice_polytope.NefPartition(data, Delta_polar, check=True)[source]¶
Bases:
SageObject,HashableCreate a nef-partition.
INPUT:
data– list of integers, the \(i\)-th element of this list must be the part of the \(i\)-th vertex ofDelta_polarin this nef-partition;Delta_polar– alattice polytope;check– by default the input will be checked for correctness, i.e. thatdataindeed specify a nef-partition. If you are sure that the input is correct, you can speed up construction viacheck=Falseoption.
OUTPUT: a nef-partition of
Delta_polarLet \(M\) and \(N\) be dual lattices. Let \(\Delta \subset M_\RR\) be a reflexive polytope with polar \(\Delta^\circ \subset N_\RR\). Let \(X_\Delta\) be the toric variety associated to the normal fan of \(\Delta\). A nef-partition is a decomposition of the vertex set \(V\) of \(\Delta^\circ\) into a disjoint union \(V = V_0 \sqcup V_1 \sqcup \dots \sqcup V_{k-1}\) such that divisors \(E_i = \sum_{v\in V_i} D_v\) are Cartier (here \(D_v\) are prime torus-invariant Weil divisors corresponding to vertices of \(\Delta^\circ\)). Equivalently, let \(\nabla_i \subset N_\RR\) be the convex hull of vertices from \(V_i\) and the origin. These polytopes form a nef-partition if their Minkowski sum \(\nabla \subset N_\RR\) is a reflexive polytope.
The dual nef-partition is formed by polytopes \(\Delta_i \subset M_\RR\) of \(E_i\), which give a decomposition of the vertex set of \(\nabla^\circ \subset M_\RR\) and their Minkowski sum is \(\Delta\), i.e. the polar duality of reflexive polytopes switches convex hull and Minkowski sum for dual nef-partitions:
\[\begin{split}\Delta^\circ &= \mathrm{Conv} \left(\nabla_0, \nabla_1, \dots, \nabla_{k-1}\right), \\ \nabla^{\phantom{\circ}} &= \nabla_0 + \nabla_1 + \dots + \nabla_{k-1}, \\ & \\ \Delta^{\phantom{\circ}} &= \Delta_0 + \Delta_1 + \dots + \Delta_{k-1}, \\ \nabla^\circ &= \mathrm{Conv} \left(\Delta_0, \Delta_1, \dots, \Delta_{k-1}\right).\end{split}\]One can also interpret the duality of nef-partitions as the duality of the associated cones. Below \(\overline{M} = M \times \ZZ^k\) and \(\overline{N} = N \times \ZZ^k\) are dual lattices.
The Cayley polytope \(P \subset \overline{M}_\RR\) of a nef-partition is given by \(P = \mathrm{Conv}(\Delta_0 \times e_0, \Delta_1 \times e_1, \ldots, \Delta_{k-1} \times e_{k-1})\), where \(\{e_i\}_{i=0}^{k-1}\) is the standard basis of \(\ZZ^k\). The dual Cayley polytope \(P^* \subset \overline{N}_\RR\) is the Cayley polytope of the dual nef-partition.
The Cayley cone \(C \subset \overline{M}_\RR\) of a nef-partition is the cone spanned by its Cayley polytope. The dual Cayley cone \(C^\vee \subset \overline{M}_\RR\) is the usual dual cone of \(C\). It turns out, that \(C^\vee\) is spanned by \(P^*\).
It is also possible to go back from the Cayley cone to the Cayley polytope, since \(C\) is a reflexive Gorenstein cone supported by \(P\): primitive integral ray generators of \(C\) are contained in an affine hyperplane and coincide with vertices of \(P\).
See Section 4.3.1 in [CK1999] and references therein for further details, or [BN2008] for a purely combinatorial approach.
EXAMPLES:
It is very easy to create a nef-partition for the octahedron, since for this polytope any decomposition of vertices is a nef-partition. We create a 3-part nef-partition with the 0th and 1st vertices belonging to the 0th part (recall that numeration in Sage starts with 0), the 2nd and 5th vertices belonging to the 1st part, and 3rd and 4th vertices belonging to the 2nd part:
sage: o = lattice_polytope.cross_polytope(3) sage: np = NefPartition([0,0,1,2,2,1], o) sage: np Nef-partition {0, 1} ⊔ {2, 5} ⊔ {3, 4}
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> np = NefPartition([Integer(0),Integer(0),Integer(1),Integer(2),Integer(2),Integer(1)], o) >>> np Nef-partition {0, 1} ⊔ {2, 5} ⊔ {3, 4}
The octahedron plays the role of \(\Delta^\circ\) in the above description:
sage: np.Delta_polar() is o True
>>> from sage.all import * >>> np.Delta_polar() is o True
The dual nef-partition (corresponding to the “mirror complete intersection”) gives decomposition of the vertex set of \(\nabla^\circ\):
sage: np.dual() Nef-partition {0, 1, 2} ⊔ {3, 4} ⊔ {5, 6, 7} sage: np.nabla_polar().vertices() N(-1, -1, 0), N(-1, 0, 0), N( 0, -1, 0), N( 0, 0, -1), N( 0, 0, 1), N( 1, 0, 0), N( 0, 1, 0), N( 1, 1, 0) in 3-d lattice N
>>> from sage.all import * >>> np.dual() Nef-partition {0, 1, 2} ⊔ {3, 4} ⊔ {5, 6, 7} >>> np.nabla_polar().vertices() N(-1, -1, 0), N(-1, 0, 0), N( 0, -1, 0), N( 0, 0, -1), N( 0, 0, 1), N( 1, 0, 0), N( 0, 1, 0), N( 1, 1, 0) in 3-d lattice N
Of course, \(\nabla^\circ\) is \(\Delta^\circ\) from the point of view of the dual nef-partition:
sage: np.dual().Delta_polar() is np.nabla_polar() True sage: np.Delta(1).vertices() N(0, 0, -1), N(0, 0, 1) in 3-d lattice N sage: np.dual().nabla(1).vertices() N(0, 0, -1), N(0, 0, 1) in 3-d lattice N
>>> from sage.all import * >>> np.dual().Delta_polar() is np.nabla_polar() True >>> np.Delta(Integer(1)).vertices() N(0, 0, -1), N(0, 0, 1) in 3-d lattice N >>> np.dual().nabla(Integer(1)).vertices() N(0, 0, -1), N(0, 0, 1) in 3-d lattice N
Instead of constructing nef-partitions directly, you can request all 2-part nef-partitions of a given reflexive polytope (they will be computed using
nef.xprogram from PALP):sage: o.nef_partitions() # needs palp [ Nef-partition {0, 1, 3} ⊔ {2, 4, 5}, Nef-partition {0, 1, 3, 4} ⊔ {2, 5} (direct product), Nef-partition {0, 1, 2} ⊔ {3, 4, 5}, Nef-partition {0, 1, 2, 3} ⊔ {4, 5}, Nef-partition {0, 1, 2, 3, 4} ⊔ {5} (projection) ]
>>> from sage.all import * >>> o.nef_partitions() # needs palp [ Nef-partition {0, 1, 3} ⊔ {2, 4, 5}, Nef-partition {0, 1, 3, 4} ⊔ {2, 5} (direct product), Nef-partition {0, 1, 2} ⊔ {3, 4, 5}, Nef-partition {0, 1, 2, 3} ⊔ {4, 5}, Nef-partition {0, 1, 2, 3, 4} ⊔ {5} (projection) ]
- Delta(i=None)[source]¶
Return the polytope \(\Delta\) or \(\Delta_i\) corresponding to
self.INPUT:
i– integer; if not given, \(\Delta\) will be returned
OUTPUT: a
lattice polytopeSee
nef-partitionclass documentation for definitions and notation.EXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: np = NefPartition([0, 0, 1, 0, 1, 1], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} sage: np.Delta().polar() is o True sage: np.Delta().vertices() N( 1, -1, -1), N( 1, 1, -1), N( 1, 1, 1), N( 1, -1, 1), N(-1, -1, 1), N(-1, -1, -1), N(-1, 1, -1), N(-1, 1, 1) in 3-d lattice N sage: np.Delta(0).vertices() N(-1, -1, 0), N(-1, 0, 0), N( 1, 0, 0), N( 1, -1, 0) in 3-d lattice N
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> np = NefPartition([Integer(0), Integer(0), Integer(1), Integer(0), Integer(1), Integer(1)], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} >>> np.Delta().polar() is o True >>> np.Delta().vertices() N( 1, -1, -1), N( 1, 1, -1), N( 1, 1, 1), N( 1, -1, 1), N(-1, -1, 1), N(-1, -1, -1), N(-1, 1, -1), N(-1, 1, 1) in 3-d lattice N >>> np.Delta(Integer(0)).vertices() N(-1, -1, 0), N(-1, 0, 0), N( 1, 0, 0), N( 1, -1, 0) in 3-d lattice N
- Delta_polar()[source]¶
Return the polytope \(\Delta^\circ\) corresponding to
self.OUTPUT: a
lattice polytopeSee
nef-partitionclass documentation for definitions and notation.EXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: np = NefPartition([0, 0, 1, 0, 1, 1], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} sage: np.Delta_polar() is o True
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> np = NefPartition([Integer(0), Integer(0), Integer(1), Integer(0), Integer(1), Integer(1)], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} >>> np.Delta_polar() is o True
- Deltas()[source]¶
Return the polytopes \(\Delta_i\) corresponding to
self.OUTPUT: a tuple of
lattice polytopesSee
nef-partitionclass documentation for definitions and notation.EXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: np = NefPartition([0, 0, 1, 0, 1, 1], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} sage: np.Delta().vertices() N( 1, -1, -1), N( 1, 1, -1), N( 1, 1, 1), N( 1, -1, 1), N(-1, -1, 1), N(-1, -1, -1), N(-1, 1, -1), N(-1, 1, 1) in 3-d lattice N sage: [Delta_i.vertices() for Delta_i in np.Deltas()] [N(-1, -1, 0), N(-1, 0, 0), N( 1, 0, 0), N( 1, -1, 0) in 3-d lattice N, N(0, 0, -1), N(0, 1, 1), N(0, 0, 1), N(0, 1, -1) in 3-d lattice N] sage: np.nabla_polar().vertices() N(-1, -1, 0), N( 1, -1, 0), N( 1, 0, 0), N(-1, 0, 0), N( 0, 1, -1), N( 0, 1, 1), N( 0, 0, 1), N( 0, 0, -1) in 3-d lattice N
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> np = NefPartition([Integer(0), Integer(0), Integer(1), Integer(0), Integer(1), Integer(1)], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} >>> np.Delta().vertices() N( 1, -1, -1), N( 1, 1, -1), N( 1, 1, 1), N( 1, -1, 1), N(-1, -1, 1), N(-1, -1, -1), N(-1, 1, -1), N(-1, 1, 1) in 3-d lattice N >>> [Delta_i.vertices() for Delta_i in np.Deltas()] [N(-1, -1, 0), N(-1, 0, 0), N( 1, 0, 0), N( 1, -1, 0) in 3-d lattice N, N(0, 0, -1), N(0, 1, 1), N(0, 0, 1), N(0, 1, -1) in 3-d lattice N] >>> np.nabla_polar().vertices() N(-1, -1, 0), N( 1, -1, 0), N( 1, 0, 0), N(-1, 0, 0), N( 0, 1, -1), N( 0, 1, 1), N( 0, 0, 1), N( 0, 0, -1) in 3-d lattice N
- dual()[source]¶
Return the dual nef-partition.
OUTPUT: a
nef-partitionSee the class documentation for the definition.
ALGORITHM:
See Proposition 3.19 in [BN2008].
Note
Automatically constructed dual nef-partitions will be ordered, i.e. vertex partition of \(\nabla\) will look like \(\{0, 1, 2\} \sqcup \{3, 4, 5, 6\} \sqcup \{7, 8\}\).
EXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: np = NefPartition([0, 0, 1, 0, 1, 1], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} sage: np.dual() Nef-partition {0, 1, 2, 3} ⊔ {4, 5, 6, 7} sage: np.dual().Delta() is np.nabla() True sage: np.dual().nabla(0) is np.Delta(0) True
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> np = NefPartition([Integer(0), Integer(0), Integer(1), Integer(0), Integer(1), Integer(1)], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} >>> np.dual() Nef-partition {0, 1, 2, 3} ⊔ {4, 5, 6, 7} >>> np.dual().Delta() is np.nabla() True >>> np.dual().nabla(Integer(0)) is np.Delta(Integer(0)) True
- hodge_numbers()[source]¶
Return Hodge numbers corresponding to
self.OUTPUT: a tuple of integers (produced by
nef.xprogram from PALP)EXAMPLES:
Currently, you need to request Hodge numbers when you compute nef-partitions:
sage: # long time, needs palp sage: p = lattice_polytope.cross_polytope(5) sage: np = p.nef_partitions()[0] # 4s on sage.math, 2011 sage: np.hodge_numbers() Traceback (most recent call last): ... NotImplementedError: use nef_partitions(hodge_numbers=True)! sage: np = p.nef_partitions(hodge_numbers=True)[0] # 13s on sage.math, 2011 sage: np.hodge_numbers() (19, 19)
>>> from sage.all import * >>> # long time, needs palp >>> p = lattice_polytope.cross_polytope(Integer(5)) >>> np = p.nef_partitions()[Integer(0)] # 4s on sage.math, 2011 >>> np.hodge_numbers() Traceback (most recent call last): ... NotImplementedError: use nef_partitions(hodge_numbers=True)! >>> np = p.nef_partitions(hodge_numbers=True)[Integer(0)] # 13s on sage.math, 2011 >>> np.hodge_numbers() (19, 19)
- nabla(i=None)[source]¶
Return the polytope \(\nabla\) or \(\nabla_i\) corresponding to
self.INPUT:
i– integer; if not given, \(\nabla\) will be returned
OUTPUT: a
lattice polytopeSee
nef-partitionclass documentation for definitions and notation.EXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: np = NefPartition([0, 0, 1, 0, 1, 1], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} sage: np.Delta_polar().vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M sage: np.nabla(0).vertices() M(-1, 0, 0), M( 1, 0, 0), M( 0, 1, 0) in 3-d lattice M sage: np.nabla().vertices() M(-1, 0, 1), M(-1, 0, -1), M( 1, 0, 1), M( 1, 0, -1), M( 0, 1, 1), M( 0, 1, -1), M( 1, -1, 0), M(-1, -1, 0) in 3-d lattice M
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> np = NefPartition([Integer(0), Integer(0), Integer(1), Integer(0), Integer(1), Integer(1)], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} >>> np.Delta_polar().vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M >>> np.nabla(Integer(0)).vertices() M(-1, 0, 0), M( 1, 0, 0), M( 0, 1, 0) in 3-d lattice M >>> np.nabla().vertices() M(-1, 0, 1), M(-1, 0, -1), M( 1, 0, 1), M( 1, 0, -1), M( 0, 1, 1), M( 0, 1, -1), M( 1, -1, 0), M(-1, -1, 0) in 3-d lattice M
- nabla_polar()[source]¶
Return the polytope \(\nabla^\circ\) corresponding to
self.OUTPUT: a
lattice polytopeSee
nef-partitionclass documentation for definitions and notation.EXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: np = NefPartition([0, 0, 1, 0, 1, 1], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} sage: np.nabla_polar().vertices() N(-1, -1, 0), N( 1, -1, 0), N( 1, 0, 0), N(-1, 0, 0), N( 0, 1, -1), N( 0, 1, 1), N( 0, 0, 1), N( 0, 0, -1) in 3-d lattice N sage: np.nabla_polar() is np.dual().Delta_polar() True
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> np = NefPartition([Integer(0), Integer(0), Integer(1), Integer(0), Integer(1), Integer(1)], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} >>> np.nabla_polar().vertices() N(-1, -1, 0), N( 1, -1, 0), N( 1, 0, 0), N(-1, 0, 0), N( 0, 1, -1), N( 0, 1, 1), N( 0, 0, 1), N( 0, 0, -1) in 3-d lattice N >>> np.nabla_polar() is np.dual().Delta_polar() True
- nablas()[source]¶
Return the polytopes \(\nabla_i\) corresponding to
self.OUTPUT: a tuple of
lattice polytopesSee
nef-partitionclass documentation for definitions and notation.EXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: np = NefPartition([0, 0, 1, 0, 1, 1], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} sage: np.Delta_polar().vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M sage: [nabla_i.vertices() for nabla_i in np.nablas()] [M(-1, 0, 0), M( 1, 0, 0), M( 0, 1, 0) in 3-d lattice M, M(0, -1, 0), M(0, 0, -1), M(0, 0, 1) in 3-d lattice M]
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> np = NefPartition([Integer(0), Integer(0), Integer(1), Integer(0), Integer(1), Integer(1)], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} >>> np.Delta_polar().vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M >>> [nabla_i.vertices() for nabla_i in np.nablas()] [M(-1, 0, 0), M( 1, 0, 0), M( 0, 1, 0) in 3-d lattice M, M(0, -1, 0), M(0, 0, -1), M(0, 0, 1) in 3-d lattice M]
- nparts()[source]¶
Return the number of parts in
self.OUTPUT: integer
EXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: np = NefPartition([0, 0, 1, 0, 1, 1], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} sage: np.nparts() 2
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> np = NefPartition([Integer(0), Integer(0), Integer(1), Integer(0), Integer(1), Integer(1)], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} >>> np.nparts() 2
- part(i, all_points=False)[source]¶
Return the
i-th part ofself.INPUT:
i– integerall_points– boolean (default:False); whether to list all lattice points or just vertices
OUTPUT:
a tuple of integers, indices of vertices (or all lattice points) of \(\Delta^\circ\) belonging to \(V_i\).
See
nef-partitionclass documentation for definitions and notation.EXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: np = NefPartition([0, 0, 1, 0, 1, 1], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} sage: np.part(0) (0, 1, 3) sage: np.part(0, all_points=True) # needs palp (0, 1, 3) sage: np.dual().part(0) (0, 1, 2, 3) sage: np.dual().part(0, all_points=True) # needs palp (0, 1, 2, 3, 8)
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> np = NefPartition([Integer(0), Integer(0), Integer(1), Integer(0), Integer(1), Integer(1)], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} >>> np.part(Integer(0)) (0, 1, 3) >>> np.part(Integer(0), all_points=True) # needs palp (0, 1, 3) >>> np.dual().part(Integer(0)) (0, 1, 2, 3) >>> np.dual().part(Integer(0), all_points=True) # needs palp (0, 1, 2, 3, 8)
- part_of(i)[source]¶
Return the index of the part containing the
i-th vertex.INPUT:
i– integer
OUTPUT:
an integer \(j\) such that the
i-th vertex of \(\Delta^\circ\) belongs to \(V_j\).
See
nef-partitionclass documentation for definitions and notation.EXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: np = NefPartition([0, 0, 1, 0, 1, 1], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} sage: np.part_of(3) 0 sage: np.part_of(2) 1
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> np = NefPartition([Integer(0), Integer(0), Integer(1), Integer(0), Integer(1), Integer(1)], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} >>> np.part_of(Integer(3)) 0 >>> np.part_of(Integer(2)) 1
- part_of_point(i)[source]¶
Return the index of the part containing the
i-th point.INPUT:
i– integer
OUTPUT:
an integer \(j\) such that the
i-th point of \(\Delta^\circ\) belongs to \(\nabla_j\).
Note
Since a nef-partition induces a partition on the set of boundary lattice points of \(\Delta^\circ\), the value of \(j\) is well-defined for all \(i\) but the one that corresponds to the origin, in which case this method will raise a
ValueErrorexception. (The origin always belongs to all \(\nabla_j\).)See
nef-partitionclass documentation for definitions and notation.EXAMPLES:
We consider a relatively complicated reflexive polytope #2252 (easily accessible in Sage as
ReflexivePolytope(3, 2252), we create it here explicitly to avoid loading the whole database):sage: p = LatticePolytope([(1,0,0), (0,1,0), (0,0,1), (0,1,-1), ....: (0,-1,1), (-1,1,0), (0,-1,-1), (-1,-1,0), (-1,-1,2)]) sage: np = p.nef_partitions()[0]; np # needs palp Nef-partition {1, 2, 5, 7, 8} ⊔ {0, 3, 4, 6} sage: p.nvertices() 9 sage: p.npoints() # needs palp 15
>>> from sage.all import * >>> p = LatticePolytope([(Integer(1),Integer(0),Integer(0)), (Integer(0),Integer(1),Integer(0)), (Integer(0),Integer(0),Integer(1)), (Integer(0),Integer(1),-Integer(1)), ... (Integer(0),-Integer(1),Integer(1)), (-Integer(1),Integer(1),Integer(0)), (Integer(0),-Integer(1),-Integer(1)), (-Integer(1),-Integer(1),Integer(0)), (-Integer(1),-Integer(1),Integer(2))]) >>> np = p.nef_partitions()[Integer(0)]; np # needs palp Nef-partition {1, 2, 5, 7, 8} ⊔ {0, 3, 4, 6} >>> p.nvertices() 9 >>> p.npoints() # needs palp 15
We see that the polytope has 6 more points in addition to vertices. One of them is the origin:
sage: p.origin() # needs palp 14 sage: np.part_of_point(14) # needs palp Traceback (most recent call last): ... ValueError: the origin belongs to all parts!
>>> from sage.all import * >>> p.origin() # needs palp 14 >>> np.part_of_point(Integer(14)) # needs palp Traceback (most recent call last): ... ValueError: the origin belongs to all parts!
But the remaining 5 are partitioned by
np:sage: [n for n in range(p.npoints()) # needs palp ....: if p.origin() != n and np.part_of_point(n) == 0] [1, 2, 5, 7, 8, 9, 11, 13] sage: [n for n in range(p.npoints()) # needs palp ....: if p.origin() != n and np.part_of_point(n) == 1] [0, 3, 4, 6, 10, 12]
>>> from sage.all import * >>> [n for n in range(p.npoints()) # needs palp ... if p.origin() != n and np.part_of_point(n) == Integer(0)] [1, 2, 5, 7, 8, 9, 11, 13] >>> [n for n in range(p.npoints()) # needs palp ... if p.origin() != n and np.part_of_point(n) == Integer(1)] [0, 3, 4, 6, 10, 12]
- parts(all_points=False)[source]¶
Return all parts of
self.INPUT:
all_points– boolean (default:False); whether to list all lattice points or just vertices
OUTPUT:
a tuple of tuples of integers. The \(i\)-th tuple contains indices of vertices (or all lattice points) of \(\Delta^\circ\) belonging to \(V_i\)
See
nef-partitionclass documentation for definitions and notation.EXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: np = NefPartition([0, 0, 1, 0, 1, 1], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} sage: np.parts() ((0, 1, 3), (2, 4, 5)) sage: np.parts(all_points=True) # needs palp ((0, 1, 3), (2, 4, 5)) sage: np.dual().parts() ((0, 1, 2, 3), (4, 5, 6, 7)) sage: np.dual().parts(all_points=True) # needs palp ((0, 1, 2, 3, 8), (4, 5, 6, 7, 10))
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> np = NefPartition([Integer(0), Integer(0), Integer(1), Integer(0), Integer(1), Integer(1)], o); np Nef-partition {0, 1, 3} ⊔ {2, 4, 5} >>> np.parts() ((0, 1, 3), (2, 4, 5)) >>> np.parts(all_points=True) # needs palp ((0, 1, 3), (2, 4, 5)) >>> np.dual().parts() ((0, 1, 2, 3), (4, 5, 6, 7)) >>> np.dual().parts(all_points=True) # needs palp ((0, 1, 2, 3, 8), (4, 5, 6, 7, 10))
- sage.geometry.lattice_polytope.ReflexivePolytope(dim, n)[source]¶
Return the \(n\)-th 2- or 3-dimensional reflexive polytope.
Note
Numeration starts with zero: \(0 \leq n \leq 15\) for \({\rm dim} = 2\) and \(0 \leq n \leq 4318\) for \({\rm dim} = 3\).
During the first call, all reflexive polytopes of requested dimension are loaded and cached for future use, so the first call for 3-dimensional polytopes can take several seconds, but all consecutive calls are fast.
Equivalent to
ReflexivePolytopes(dim)[n]but checks bounds first.
EXAMPLES:
The 3rd 2-dimensional polytope is “the diamond”:
sage: ReflexivePolytope(2, 3) 2-d reflexive polytope #3 in 2-d lattice M sage: lattice_polytope.ReflexivePolytope(2,3).vertices() M( 1, 0), M( 0, 1), M( 0, -1), M(-1, 0) in 2-d lattice M
>>> from sage.all import * >>> ReflexivePolytope(Integer(2), Integer(3)) 2-d reflexive polytope #3 in 2-d lattice M >>> lattice_polytope.ReflexivePolytope(Integer(2),Integer(3)).vertices() M( 1, 0), M( 0, 1), M( 0, -1), M(-1, 0) in 2-d lattice M
There are 16 reflexive polygons and numeration starts with 0:
sage: ReflexivePolytope(2,16) Traceback (most recent call last): ... ValueError: there are only 16 reflexive polygons!
>>> from sage.all import * >>> ReflexivePolytope(Integer(2),Integer(16)) Traceback (most recent call last): ... ValueError: there are only 16 reflexive polygons!
It is not possible to load a 4-dimensional polytope in this way:
sage: ReflexivePolytope(4,16) Traceback (most recent call last): ... NotImplementedError: only 2- and 3-dimensional reflexive polytopes are available!
>>> from sage.all import * >>> ReflexivePolytope(Integer(4),Integer(16)) Traceback (most recent call last): ... NotImplementedError: only 2- and 3-dimensional reflexive polytopes are available!
- sage.geometry.lattice_polytope.ReflexivePolytopes(dim)[source]¶
Return the sequence of all 2- or 3-dimensional reflexive polytopes.
Note
During the first call the database is loaded and cached for future use, so repetitive calls will return the same object in memory.
INPUT:
dim– integer (2 or 3); dimension of required reflexive polytopes
OUTPUT: list of lattice polytopes
EXAMPLES:
There are 16 reflexive polygons:
sage: len(ReflexivePolytopes(2)) 16
>>> from sage.all import * >>> len(ReflexivePolytopes(Integer(2))) 16
It is not possible to load 4-dimensional polytopes in this way:
sage: ReflexivePolytopes(4) Traceback (most recent call last): ... NotImplementedError: only 2- and 3-dimensional reflexive polytopes are available!
>>> from sage.all import * >>> ReflexivePolytopes(Integer(4)) Traceback (most recent call last): ... NotImplementedError: only 2- and 3-dimensional reflexive polytopes are available!
- class sage.geometry.lattice_polytope.SetOfAllLatticePolytopesClass[source]¶
Bases:
Set_generic
- sage.geometry.lattice_polytope.all_cached_data(polytopes)[source]¶
Compute all cached data for all given
polytopesand their polars.This functions does it MUCH faster than member functions of
LatticePolytopeduring the first run. So it is recommended to use this functions if you work with big sets of data. None of the polytopes in the given sequence should be constructed as the polar polytope to another one.INPUT:
polytopes– a sequence of lattice polytopes
EXAMPLES: This function has no output, it is just a fast way to work with long sequences of polytopes. Of course, you can use short sequences as well:
sage: o = lattice_polytope.cross_polytope(3) sage: lattice_polytope.all_cached_data([o]) # needs palp
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> lattice_polytope.all_cached_data([o]) # needs palp
- sage.geometry.lattice_polytope.all_facet_equations(polytopes)[source]¶
Compute polar polytopes for all reflexive and equations of facets for all non-reflexive
polytopes.all_facet_equationsandall_polarsare synonyms.This functions does it MUCH faster than member functions of
LatticePolytopeduring the first run. So it is recommended to use this functions if you work with big sets of data.INPUT:
polytopes– a sequence of lattice polytopes
EXAMPLES: This function has no output, it is just a fast way to work with long sequences of polytopes. Of course, you can use short sequences as well:
sage: o = lattice_polytope.cross_polytope(3) sage: lattice_polytope.all_polars([o]) # needs palp sage: o.polar() # needs palp 3-d reflexive polytope in 3-d lattice N
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> lattice_polytope.all_polars([o]) # needs palp >>> o.polar() # needs palp 3-d reflexive polytope in 3-d lattice N
- sage.geometry.lattice_polytope.all_nef_partitions(polytopes, keep_symmetric=False)[source]¶
Compute nef-partitions for all given
polytopes.This functions does it MUCH faster than member functions of
LatticePolytopeduring the first run. So it is recommended to use this functions if you work with big sets of data.Note: member function
is_reflexivewill be called separately for each polytope. It is strictly recommended to callall_polarson the sequence ofpolytopesbefore using this function.INPUT:
polytopes– a sequence of lattice polytopes
EXAMPLES: This function has no output, it is just a fast way to work with long sequences of polytopes. Of course, you can use short sequences as well:
sage: o = lattice_polytope.cross_polytope(3) sage: lattice_polytope.all_nef_partitions([o]) # needs palp sage: o.nef_partitions() # needs palp [ Nef-partition {0, 1, 3} ⊔ {2, 4, 5}, Nef-partition {0, 1, 3, 4} ⊔ {2, 5} (direct product), Nef-partition {0, 1, 2} ⊔ {3, 4, 5}, Nef-partition {0, 1, 2, 3} ⊔ {4, 5}, Nef-partition {0, 1, 2, 3, 4} ⊔ {5} (projection) ]
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> lattice_polytope.all_nef_partitions([o]) # needs palp >>> o.nef_partitions() # needs palp [ Nef-partition {0, 1, 3} ⊔ {2, 4, 5}, Nef-partition {0, 1, 3, 4} ⊔ {2, 5} (direct product), Nef-partition {0, 1, 2} ⊔ {3, 4, 5}, Nef-partition {0, 1, 2, 3} ⊔ {4, 5}, Nef-partition {0, 1, 2, 3, 4} ⊔ {5} (projection) ]
You cannot use this function for non-reflexive polytopes:
sage: p = LatticePolytope([(1,0,0), (0,1,0), (0,0,2), ....: (-1,0,0), (0,-1,0), (0,0,-1)]) sage: lattice_polytope.all_nef_partitions([o, p]) # needs palp Traceback (most recent call last): ... ValueError: nef-partitions can be computed for reflexive polytopes only
>>> from sage.all import * >>> p = LatticePolytope([(Integer(1),Integer(0),Integer(0)), (Integer(0),Integer(1),Integer(0)), (Integer(0),Integer(0),Integer(2)), ... (-Integer(1),Integer(0),Integer(0)), (Integer(0),-Integer(1),Integer(0)), (Integer(0),Integer(0),-Integer(1))]) >>> lattice_polytope.all_nef_partitions([o, p]) # needs palp Traceback (most recent call last): ... ValueError: nef-partitions can be computed for reflexive polytopes only
- sage.geometry.lattice_polytope.all_points(polytopes)[source]¶
Compute lattice points for all given
polytopes.This functions does it MUCH faster than member functions of
LatticePolytopeduring the first run. So it is recommended to use this functions if you work with big sets of data.INPUT:
polytopes– a sequence of lattice polytopes
EXAMPLES: This function has no output, it is just a fast way to work with long sequences of polytopes. Of course, you can use short sequences as well:
sage: o = lattice_polytope.cross_polytope(3) sage: lattice_polytope.all_points([o]) # needs palp sage: o.points() # needs palp M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1), M( 0, 0, 0) in 3-d lattice M
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> lattice_polytope.all_points([o]) # needs palp >>> o.points() # needs palp M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1), M( 0, 0, 0) in 3-d lattice M
- sage.geometry.lattice_polytope.all_polars(polytopes)[source]¶
Compute polar polytopes for all reflexive and equations of facets for all non-reflexive
polytopes.all_facet_equationsandall_polarsare synonyms.This functions does it MUCH faster than member functions of
LatticePolytopeduring the first run. So it is recommended to use this functions if you work with big sets of data.INPUT:
polytopes– a sequence of lattice polytopes
EXAMPLES: This function has no output, it is just a fast way to work with long sequences of polytopes. Of course, you can use short sequences as well:
sage: o = lattice_polytope.cross_polytope(3) sage: lattice_polytope.all_polars([o]) # needs palp sage: o.polar() # needs palp 3-d reflexive polytope in 3-d lattice N
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> lattice_polytope.all_polars([o]) # needs palp >>> o.polar() # needs palp 3-d reflexive polytope in 3-d lattice N
- sage.geometry.lattice_polytope.convex_hull(points)[source]¶
Compute the convex hull of the given points.
Note
pointsmight not span the space. Also, it fails for large numbers of vertices in dimensions 4 or greaterINPUT:
points– list that can be converted into vectors of the same dimension over \(\ZZ\)
OUTPUT: list of vertices of the convex hull of the given points (as vectors)
EXAMPLES: Let’s compute the convex hull of several points on a line in the plane:
sage: lattice_polytope.convex_hull([[1,2],[3,4],[5,6],[7,8]]) [(1, 2), (7, 8)]
>>> from sage.all import * >>> lattice_polytope.convex_hull([[Integer(1),Integer(2)],[Integer(3),Integer(4)],[Integer(5),Integer(6)],[Integer(7),Integer(8)]]) [(1, 2), (7, 8)]
- sage.geometry.lattice_polytope.cross_polytope(dim)[source]¶
Return a cross-polytope of the given dimension.
INPUT:
dim– integer
OUTPUT: a
lattice polytopeEXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: o 3-d reflexive polytope in 3-d lattice M sage: o.vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> o 3-d reflexive polytope in 3-d lattice M >>> o.vertices() M( 1, 0, 0), M( 0, 1, 0), M( 0, 0, 1), M(-1, 0, 0), M( 0, -1, 0), M( 0, 0, -1) in 3-d lattice M
- sage.geometry.lattice_polytope.is_LatticePolytope(x)[source]¶
Check if
xis a lattice polytope.INPUT:
x– anything
OUTPUT:
Trueifxis alattice polytope,Falseotherwise.
EXAMPLES:
sage: from sage.geometry.lattice_polytope import is_LatticePolytope sage: is_LatticePolytope(1) doctest:warning... DeprecationWarning: is_LatticePolytope is deprecated, use isinstance instead See https://github.com/sagemath/sage/issues/34307 for details. False sage: p = LatticePolytope([(1,0), (0,1), (-1,-1)]) sage: p # needs palp 2-d reflexive polytope #0 in 2-d lattice M sage: is_LatticePolytope(p) True
>>> from sage.all import * >>> from sage.geometry.lattice_polytope import is_LatticePolytope >>> is_LatticePolytope(Integer(1)) doctest:warning... DeprecationWarning: is_LatticePolytope is deprecated, use isinstance instead See https://github.com/sagemath/sage/issues/34307 for details. False >>> p = LatticePolytope([(Integer(1),Integer(0)), (Integer(0),Integer(1)), (-Integer(1),-Integer(1))]) >>> p # needs palp 2-d reflexive polytope #0 in 2-d lattice M >>> is_LatticePolytope(p) True
- sage.geometry.lattice_polytope.is_NefPartition(x)[source]¶
Check if
xis a nef-partition.INPUT:
x– anything
OUTPUT:
Trueifxis anef-partitionandFalseotherwise.
EXAMPLES:
sage: from sage.geometry.lattice_polytope import NefPartition sage: isinstance(1, NefPartition) False sage: o = lattice_polytope.cross_polytope(3) sage: np = o.nef_partitions()[0]; np # needs palp Nef-partition {0, 1, 3} ⊔ {2, 4, 5} sage: isinstance(np, NefPartition) # needs palp True
>>> from sage.all import * >>> from sage.geometry.lattice_polytope import NefPartition >>> isinstance(Integer(1), NefPartition) False >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> np = o.nef_partitions()[Integer(0)]; np # needs palp Nef-partition {0, 1, 3} ⊔ {2, 4, 5} >>> isinstance(np, NefPartition) # needs palp True
- sage.geometry.lattice_polytope.minkowski_sum(points1, points2)[source]¶
Compute the Minkowski sum of two convex polytopes.
Note
Polytopes might not be of maximal dimension.
INPUT:
points1,points2– lists of objects that can be converted into vectors of the same dimension, treated as vertices of two polytopes.
OUTPUT: list of vertices of the Minkowski sum, given as vectors
EXAMPLES: Let’s compute the Minkowski sum of two line segments:
sage: lattice_polytope.minkowski_sum([[1,0],[-1,0]],[[0,1],[0,-1]]) [(1, 1), (1, -1), (-1, 1), (-1, -1)]
>>> from sage.all import * >>> lattice_polytope.minkowski_sum([[Integer(1),Integer(0)],[-Integer(1),Integer(0)]],[[Integer(0),Integer(1)],[Integer(0),-Integer(1)]]) [(1, 1), (1, -1), (-1, 1), (-1, -1)]
- sage.geometry.lattice_polytope.positive_integer_relations(points)[source]¶
Return relations between given points.
INPUT:
points– lattice points given as columns of a matrix
OUTPUT: matrix of relations between given points with nonnegative integer coefficients
EXAMPLES: This is a 3-dimensional reflexive polytope:
sage: p = LatticePolytope([(1,0,0), (0,1,0), ....: (-1,-1,0), (0,0,1), (-1,0,-1)]) sage: p.points() # needs palp M( 1, 0, 0), M( 0, 1, 0), M(-1, -1, 0), M( 0, 0, 1), M(-1, 0, -1), M( 0, 0, 0) in 3-d lattice M
>>> from sage.all import * >>> p = LatticePolytope([(Integer(1),Integer(0),Integer(0)), (Integer(0),Integer(1),Integer(0)), ... (-Integer(1),-Integer(1),Integer(0)), (Integer(0),Integer(0),Integer(1)), (-Integer(1),Integer(0),-Integer(1))]) >>> p.points() # needs palp M( 1, 0, 0), M( 0, 1, 0), M(-1, -1, 0), M( 0, 0, 1), M(-1, 0, -1), M( 0, 0, 0) in 3-d lattice M
We can compute linear relations between its points in the following way:
sage: p.points().matrix().kernel().echelonized_basis_matrix() # needs palp [ 1 0 0 1 1 0] [ 0 1 1 -1 -1 0] [ 0 0 0 0 0 1]
>>> from sage.all import * >>> p.points().matrix().kernel().echelonized_basis_matrix() # needs palp [ 1 0 0 1 1 0] [ 0 1 1 -1 -1 0] [ 0 0 0 0 0 1]
However, the above relations may contain negative and rational numbers. This function transforms them in such a way, that all coefficients are nonnegative integers:
sage: points = p.points().column_matrix() sage: lattice_polytope.positive_integer_relations(points) # needs palp [1 0 0 1 1 0] [1 1 1 0 0 0] [0 0 0 0 0 1] sage: cm = ReflexivePolytope(2,1).vertices().column_matrix() sage: lattice_polytope.positive_integer_relations(cm) [2 1 1]
>>> from sage.all import * >>> points = p.points().column_matrix() >>> lattice_polytope.positive_integer_relations(points) # needs palp [1 0 0 1 1 0] [1 1 1 0 0 0] [0 0 0 0 0 1] >>> cm = ReflexivePolytope(Integer(2),Integer(1)).vertices().column_matrix() >>> lattice_polytope.positive_integer_relations(cm) [2 1 1]
- sage.geometry.lattice_polytope.read_all_polytopes(file_name)[source]¶
Read all polytopes from the given file.
INPUT:
file_name– string with the name of a file with VERTICES of polytopes
OUTPUT: a sequence of polytopes
EXAMPLES:
We use
poly.xto compute two polar polytopes and read them:sage: # needs palp sage: d = lattice_polytope.cross_polytope(2) sage: o = lattice_polytope.cross_polytope(3) sage: result_name = lattice_polytope._palp("poly.x -fe", [d, o]) sage: with open(result_name) as f: ....: print(f.read()) 4 2 Vertices of P-dual <-> Equations of P -1 1 1 1 -1 -1 1 -1 8 3 Vertices of P-dual <-> Equations of P -1 -1 1 1 -1 1 -1 1 1 1 1 1 -1 -1 -1 1 -1 -1 -1 1 -1 1 1 -1 sage: lattice_polytope.read_all_polytopes(result_name) [2-d reflexive polytope #14 in 2-d lattice M, 3-d reflexive polytope in 3-d lattice M] sage: os.remove(result_name)
>>> from sage.all import * >>> # needs palp >>> d = lattice_polytope.cross_polytope(Integer(2)) >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> result_name = lattice_polytope._palp("poly.x -fe", [d, o]) >>> with open(result_name) as f: ... print(f.read()) 4 2 Vertices of P-dual <-> Equations of P -1 1 1 1 -1 -1 1 -1 8 3 Vertices of P-dual <-> Equations of P -1 -1 1 1 -1 1 -1 1 1 1 1 1 -1 -1 -1 1 -1 -1 -1 1 -1 1 1 -1 >>> lattice_polytope.read_all_polytopes(result_name) [2-d reflexive polytope #14 in 2-d lattice M, 3-d reflexive polytope in 3-d lattice M] >>> os.remove(result_name)
- sage.geometry.lattice_polytope.read_palp_matrix(data, permutation=False)[source]¶
Read and return an integer matrix from a string or an opened file.
First input line must start with two integers m and n, the number of rows and columns of the matrix. The rest of the first line is ignored. The next m lines must contain n numbers each.
If m>n, returns the transposed matrix. If the string is empty or EOF is reached, returns the empty matrix, constructed by
matrix().INPUT:
data– either a string containing the filename or the file itself containing the output by PALPpermutation– boolean (default:False); ifTrue, try to retrieve the permutation output by PALP. This parameter makes sense only when PALP computed the normal form of a lattice polytope.
OUTPUT: a matrix or a tuple of a matrix and a permutation
EXAMPLES:
sage: lattice_polytope.read_palp_matrix("2 3 comment \n 1 2 3 \n 4 5 6") [1 2 3] [4 5 6] sage: lattice_polytope.read_palp_matrix("3 2 Will be transposed \n 1 2 \n 3 4 \n 5 6") [1 3 5] [2 4 6]
>>> from sage.all import * >>> lattice_polytope.read_palp_matrix("2 3 comment \n 1 2 3 \n 4 5 6") [1 2 3] [4 5 6] >>> lattice_polytope.read_palp_matrix("3 2 Will be transposed \n 1 2 \n 3 4 \n 5 6") [1 3 5] [2 4 6]
- sage.geometry.lattice_polytope.set_palp_dimension(d)[source]¶
Set the dimension for PALP calls to
d.INPUT:
d– integer from the list[4,5,6,11]orNone
OUTPUT: none
PALP has many hard-coded limits, which must be specified before compilation, one of them is dimension. Sage includes several versions with different dimension settings (which may also affect other limits and enable certain features of PALP). You can change the version which will be used by calling this function. Such a change is not done automatically for each polytope based on its dimension, since depending on what you are doing it may be necessary to use dimensions higher than that of the input polytope.
EXAMPLES:
Let’s try to work with a 7-dimensional polytope:
sage: p = lattice_polytope.cross_polytope(7) sage: p._palp("poly.x -fv") # needs palp Traceback (most recent call last): ... ValueError: Error executing 'poly.x -fv' for the given polytope! Output: Please increase POLY_Dmax to at least 7
>>> from sage.all import * >>> p = lattice_polytope.cross_polytope(Integer(7)) >>> p._palp("poly.x -fv") # needs palp Traceback (most recent call last): ... ValueError: Error executing 'poly.x -fv' for the given polytope! Output: Please increase POLY_Dmax to at least 7
However, we can work with this polytope by changing PALP dimension to 11:
sage: lattice_polytope.set_palp_dimension(11) sage: p._palp("poly.x -fv") # needs palp '7 14 Vertices of P...'
>>> from sage.all import * >>> lattice_polytope.set_palp_dimension(Integer(11)) >>> p._palp("poly.x -fv") # needs palp '7 14 Vertices of P...'
Let’s go back to default settings:
sage: lattice_polytope.set_palp_dimension(None)
>>> from sage.all import * >>> lattice_polytope.set_palp_dimension(None)
- sage.geometry.lattice_polytope.skip_palp_matrix(data, n=1)[source]¶
Skip matrix data in a file.
INPUT:
data– opened file with blocks of matrix data in the following format: A block consisting of m+1 lines has the number m as the first element of its first line.n– (default: 1) integer, specifies how many blocks should be skipped
If EOF is reached during the process, raises
ValueErrorexception.EXAMPLES: We create a file with vertices of the square and the cube, but read only the second set:
sage: # needs palp sage: d = lattice_polytope.cross_polytope(2) sage: o = lattice_polytope.cross_polytope(3) sage: result_name = lattice_polytope._palp("poly.x -fe", [d, o]) sage: with open(result_name) as f: ....: print(f.read()) 4 2 Vertices of P-dual <-> Equations of P -1 1 1 1 -1 -1 1 -1 8 3 Vertices of P-dual <-> Equations of P -1 -1 1 1 -1 1 -1 1 1 1 1 1 -1 -1 -1 1 -1 -1 -1 1 -1 1 1 -1 sage: f = open(result_name) sage: lattice_polytope.skip_palp_matrix(f) sage: lattice_polytope.read_palp_matrix(f) [-1 1 -1 1 -1 1 -1 1] [-1 -1 1 1 -1 -1 1 1] [ 1 1 1 1 -1 -1 -1 -1] sage: f.close() sage: os.remove(result_name)
>>> from sage.all import * >>> # needs palp >>> d = lattice_polytope.cross_polytope(Integer(2)) >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> result_name = lattice_polytope._palp("poly.x -fe", [d, o]) >>> with open(result_name) as f: ... print(f.read()) 4 2 Vertices of P-dual <-> Equations of P -1 1 1 1 -1 -1 1 -1 8 3 Vertices of P-dual <-> Equations of P -1 -1 1 1 -1 1 -1 1 1 1 1 1 -1 -1 -1 1 -1 -1 -1 1 -1 1 1 -1 >>> f = open(result_name) >>> lattice_polytope.skip_palp_matrix(f) >>> lattice_polytope.read_palp_matrix(f) [-1 1 -1 1 -1 1 -1 1] [-1 -1 1 1 -1 -1 1 1] [ 1 1 1 1 -1 -1 -1 -1] >>> f.close() >>> os.remove(result_name)
- sage.geometry.lattice_polytope.write_palp_matrix(m, ofile=None, comment='', format=None)[source]¶
Write
mintoofilein PALP format.INPUT:
m– a matrix over integers or apoint collectionofile– a file opened for writing (default:stdout)comment– string (default: empty); see output descriptionformat– a format string used to print matrix entries
OUTPUT: nothing is returned, output written to
ofilehas the formatFirst line: number_of_rows number_of_columns comment
Next number_of_rows lines: rows of the matrix.
EXAMPLES:
sage: o = lattice_polytope.cross_polytope(3) sage: lattice_polytope.write_palp_matrix(o.vertices(), comment="3D Octahedron") 3 6 3D Octahedron 1 0 0 -1 0 0 0 1 0 0 -1 0 0 0 1 0 0 -1 sage: lattice_polytope.write_palp_matrix(o.vertices(), format='%4d') 3 6 1 0 0 -1 0 0 0 1 0 0 -1 0 0 0 1 0 0 -1
>>> from sage.all import * >>> o = lattice_polytope.cross_polytope(Integer(3)) >>> lattice_polytope.write_palp_matrix(o.vertices(), comment="3D Octahedron") 3 6 3D Octahedron 1 0 0 -1 0 0 0 1 0 0 -1 0 0 0 1 0 0 -1 >>> lattice_polytope.write_palp_matrix(o.vertices(), format='%4d') 3 6 1 0 0 -1 0 0 0 1 0 0 -1 0 0 0 1 0 0 -1