Factory#

This file contains the constructor classes and functions for \(p\)-adic rings and fields.

AUTHORS:

David Roe

sage.rings.padics.factory.QpCR(p, prec=None, *args, **kwds)#

A shortcut function to create capped relative \(p\)-adic fields.

Same functionality as Qp(). See documentation for Qp() for a description of the input parameters.

EXAMPLES:

sage: QpCR(5, 40)
5-adic Field with capped relative precision 40

sage.rings.padics.factory.QpER(p, prec=None, halt=None, secure=False, *args, **kwds)#

A shortcut function to create relaxed \(p\)-adic fields.

See ZpER() for more information about this model of precision.

EXAMPLES:

sage: R = QpER(2); R                                                            # needs sage.libs.flint
2-adic Field handled with relaxed arithmetics

sage.rings.padics.factory.QpFP(p, prec=None, *args, **kwds)#

A shortcut function to create floating point \(p\)-adic fields.

Same functionality as Qp(). See documentation for Qp() for a description of the input parameters.

EXAMPLES:

sage: QpFP(5, 40)
5-adic Field with floating precision 40

sage.rings.padics.factory.QpLC(p, prec=None, *args, **kwds)#

A shortcut function to create \(p\)-adic fields with lattice precision.

See ZpLC() for more information about this model of precision.

EXAMPLES:

sage: R = QpLC(2)
sage: R
2-adic Field with lattice-cap precision

sage.rings.padics.factory.QpLF(p, prec=None, *args, **kwds)#

A shortcut function to create \(p\)-adic fields with lattice precision.

See ZpLC() for more information about this model of precision.

EXAMPLES:

sage: R = QpLF(2)
sage: R
2-adic Field with lattice-float precision

class sage.rings.padics.factory.Qp_class#

Bases: UniqueFactory

A creation function for \(p\)-adic fields.

INPUT:

p – integer: the \(p\) in \(\QQ_p\)
prec – integer (default: 20) the precision cap of the field. In the lattice capped case, prec can either be a pair (relative_cap, absolute_cap) or an integer (understood at relative cap). In the relaxed case, prec can be either a pair (default_prec, halting_prec) or an integer (understood at default precision). Except in the floating point case, individual elements keep track of their own precision. See TYPES and PRECISION below.
type – string (default: 'capped-rel') Valid types are 'capped-rel', 'floating-point', 'lattice-cap', 'lattice-float'. See TYPES and PRECISION below
print_mode – string (default: None). Valid modes are ‘series’, ‘val-unit’, ‘terse’, ‘digits’, and ‘bars’. See PRINTING below
names – string or tuple (defaults to a string representation of \(p\)). What to use whenever \(p\) is printed.
ram_name – string. Another way to specify the name; for consistency with the Qq and Zq and extension functions.
print_pos – bool (default None) Whether to only use positive integers in the representations of elements. See PRINTING below.
print_sep – string (default None) The separator character used in the 'bars' mode. See PRINTING below.
print_alphabet – tuple (default None) The encoding into digits for use in the ‘digits’ mode. See PRINTING below.
print_max_terms – integer (default None) The maximum number of terms shown. See PRINTING below.
show_prec – a boolean or a string (default None) Specify how the precision is printed. See PRINTING below.
check – bool (default True) whether to check if \(p\) is prime. Non-prime input may cause seg-faults (but can also be useful for base n expansions for example)
label – string (default None) used for lattice precision to create parents with different lattices.

OUTPUT:

The corresponding \(p\)-adic field.

TYPES AND PRECISION:

There are two main types of precision for a \(p\)-adic element. The first is relative precision, which gives the number of known \(p\)-adic digits:

sage: R = Qp(5, 20, 'capped-rel', 'series'); a = R(675); a
2*5^2 + 5^4 + O(5^22)
sage: a.precision_relative()
20

The second type of precision is absolute precision, which gives the power of \(p\) that this element is defined modulo:

sage: a.precision_absolute()
22

There are several types of \(p\)-adic fields, depending on the methods used for tracking precision. Namely, we have:

capped relative fields (type='capped-rel')
capped absolute fields (type='capped-abs')
fixed modulus fields (type='fixed-mod')
floating point fields (type='floating-point')
lattice precision fields (type='lattice-cap' or type='lattice-float')
exact fields with relaxed arithmetics (type='relaxed')

In the capped relative case, the relative precision of an element is restricted to be at most a certain value, specified at the creation of the field. Individual elements also store their own precision, so the effect of various arithmetic operations on precision is tracked. When you cast an exact element into a capped relative field, it truncates it to the precision cap of the field.

sage: R = Qp(5, 5, 'capped-rel', 'series'); a = R(4006); a
1 + 5 + 2*5^3 + 5^4 + O(5^5)
sage: b = R(4025); b
5^2 + 2*5^3 + 5^4 + 5^5 + O(5^7)
sage: a + b
1 + 5 + 5^2 + 4*5^3 + 2*5^4 + O(5^5)

In the floating point case, elements do not track their precision, but the relative precision of elements is truncated during arithmetic to the precision cap of the field.

In the lattice case, precision on elements is tracked by a global lattice that is updated after every operation, yielding better precision behavior at the cost of higher memory and runtime usage. We refer to the documentation of the function ZpLC() for a small demonstration of the capabilities of this precision model.

Finally, the model for relaxed \(p\)-adics is quite different from any of the other types. In addition to storing a finite approximation, one also stores a method for increasing the precision. A quite interesting feature with relaxed \(p\)-adics is the possibility to create (in some cases) self-referent numbers, that are numbers whose \(n\)-th digit is defined by the previous ones. We refer to the documentation of the function ZpL() for a small demonstration of the capabilities of this precision model.

PRINTING:

There are many different ways to print \(p\)-adic elements. The way elements of a given field print is controlled by options passed in at the creation of the field. There are five basic printing modes (series, val-unit, terse, digits and bars), as well as various options that either hide some information in the print representation or sometimes make print representations more compact. Note that the printing options affect whether different \(p\)-adic fields are considered equal.

series: elements are displayed as series in \(p\).

sage: R = Qp(5, print_mode='series'); a = R(70700); a
3*5^2 + 3*5^4 + 2*5^5 + 4*5^6 + O(5^22)
sage: b = R(-70700); b
2*5^2 + 4*5^3 + 5^4 + 2*5^5 + 4*5^7 + 4*5^8 + 4*5^9 + 4*5^10 + 4*5^11
 + 4*5^12 + 4*5^13 + 4*5^14 + 4*5^15 + 4*5^16 + 4*5^17 + 4*5^18
 + 4*5^19 + 4*5^20 + 4*5^21 + O(5^22)

print_pos controls whether negatives can be used in the coefficients of powers of \(p\).
sage: S = Qp(5, print_mode='series', print_pos=False); a = S(70700); a
-2*5^2 + 5^3 - 2*5^4 - 2*5^5 + 5^7 + O(5^22)
sage: b = S(-70700); b
2*5^2 - 5^3 + 2*5^4 + 2*5^5 - 5^7 + O(5^22)
print_max_terms limits the number of terms that appear.
sage: T = Qp(5, print_mode='series', print_max_terms=4); b = R(-70700); repr(b)
'2*5^2 + 4*5^3 + 5^4 + 2*5^5 + ... + O(5^22)'
names affects how the prime is printed.
sage: U.<p> = Qp(5); p
p + O(p^21)
show_prec determines how the precision is printed. It can be either ‘none’ (or equivalently False), ‘bigoh’ (or equivalently True) or ‘bigoh’. The default is False for the 'floating-point' type and True for all other types.
sage: Qp(5)(6)
1 + 5 + O(5^20)
sage: Qp(5, show_prec='none')(6)
1 + 5

sage: QpFP(5)(6)
1 + 5
print_sep and print_alphabet have no effect in series mode.

Note that print options affect equality:
sage: R == S, R == T, R == U, S == T, S == U, T == U
(False, False, False, False, False, False)

val-unit: elements are displayed as p^k*u:

sage: R = Qp(5, print_mode='val-unit'); a = R(70700); a
5^2 * 2828 + O(5^22)
sage: b = R(-707/5); b
5^-1 * 95367431639918 + O(5^19)

print_pos controls whether to use a balanced representation or not.
sage: S = Qp(5, print_mode='val-unit', print_pos=False); b = S(-70700); b
5^2 * (-2828) + O(5^22)
names affects how the prime is printed.
sage: T = Qp(5, print_mode='val-unit', names='pi'); a = T(70700); a
pi^2 * 2828 + O(pi^22)
show_prec determines how the precision is printed. It can be either ‘none’ (or equivalently False) or ‘bigoh’ (or equivalently True). The default is False for the 'floating-point' type and True for all other types.
sage: Qp(5, print_mode='val-unit', show_prec=False)(30)
5 * 6
print_max_terms, print_sep and print_alphabet have no effect.

Equality again depends on the printing options:
sage: R == S, R == T, S == T
(False, False, False)

terse: elements are displayed as an integer in base 10 or the quotient of an integer by a power of \(p\) (still in base 10):

sage: R = Qp(5, print_mode='terse'); a = R(70700); a
70700 + O(5^22)
sage: b = R(-70700); b
2384185790944925 + O(5^22)
sage: c = R(-707/5); c
95367431639918/5 + O(5^19)

The denominator, as of version 3.3, is always printed explicitly as a power of \(p\), for predictability.
sage: d = R(707/5^2); d
707/5^2 + O(5^18)
print_pos controls whether to use a balanced representation or not.
sage: S = Qp(5, print_mode='terse', print_pos=False); b = S(-70700); b
-70700 + O(5^22)
sage: c = S(-707/5); c
-707/5 + O(5^19)
name affects how the name is printed.
sage: T.<unif> = Qp(5, print_mode='terse'); c = T(-707/5); c
95367431639918/unif + O(unif^19)
sage: d = T(-707/5^10); d
95367431639918/unif^10 + O(unif^10)
show_prec determines how the precision is printed. It can be either ‘none’ (or equivalently False) or ‘bigoh’ (or equivalently True). The default is False for the 'floating-point' type and True for all other types.
sage: Qp(5, print_mode='terse', show_prec=False)(6)
6
print_max_terms, print_sep and print_alphabet have no effect.

Equality depends on printing options:
sage: R == S, R == T, S == T
(False, False, False)

digits: elements are displayed as a string of base \(p\) digits

Restriction: you can only use the digits printing mode for small primes. Namely, \(p\) must be less than the length of the alphabet tuple (default alphabet has length 62).
sage: R = Qp(5, print_mode='digits'); a = R(70700); repr(a)
'...0000000000000004230300'
sage: b = R(-70700); repr(b)
'...4444444444444440214200'
sage: c = R(-707/5); repr(c)
'...4444444444444443413.3'
sage: d = R(-707/5^2); repr(d)
'...444444444444444341.33'
Observe that the significant 0’s are printed even if they are located in front of the number. On the contrary, unknown digits located after the comma appears as question marks. The precision can therefore be read in this mode as well. Here are more examples:
sage: p = 7
sage: K = Qp(p, prec=10, print_mode='digits')
sage: repr(K(1))
'...0000000001'
sage: repr(K(p^2))
'...000000000100'
sage: repr(K(p^-5))
'...00000.00001'
sage: repr(K(p^-20))
'...?.??????????0000000001'
print_max_terms limits the number of digits that are printed. Note that if the valuation of the element is very negative, more digits will be printed.
sage: S = Qp(5, print_max_terms=4); S(-70700)
2*5^2 + 4*5^3 + 5^4 + 2*5^5 + ... + O(5^22)
sage: S(-707/5^2)
3*5^-2 + 3*5^-1 + 1 + 4*5 + ... + O(5^18)
sage: S(-707/5^6)
3*5^-6 + 3*5^-5 + 5^-4 + 4*5^-3 + ... + O(5^14)
sage: S(-707/5^6,absprec=-2)
3*5^-6 + 3*5^-5 + 5^-4 + 4*5^-3 + O(5^-2)
sage: S(-707/5^4)
3*5^-4 + 3*5^-3 + 5^-2 + 4*5^-1 + ... + O(5^16)
print_alphabet controls the symbols used to substitute for digits greater than 9.

Defaults to (‘0’, ‘1’, ‘2’, ‘3’, ‘4’, ‘5’, ‘6’, ‘7’, ‘8’, ‘9’, ‘A’, ‘B’, ‘C’, ‘D’, ‘E’, ‘F’, ‘G’, ‘H’, ‘I’, ‘J’, ‘K’, ‘L’, ‘M’, ‘N’, ‘O’, ‘P’, ‘Q’, ‘R’, ‘S’, ‘T’, ‘U’, ‘V’, ‘W’, ‘X’, ‘Y’, ‘Z’, ‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’, ‘g’, ‘h’, ‘i’, ‘j’, ‘k’, ‘l’, ‘m’, ‘n’, ‘o’, ‘p’, ‘q’, ‘r’, ‘s’, ‘t’, ‘u’, ‘v’, ‘w’, ‘x’, ‘y’, ‘z’):
sage: T = Qp(5, print_mode='digits', print_alphabet=('1','2','3','4','5')); repr(T(-70700))
'...5555555555555551325311'
show_prec determines how the precision is printed. It can be either ‘none’ (or equivalently False), ‘dots’ (or equivalently True) or ‘bigoh’. The default is False for the 'floating-point' type and True for all other types.
sage: repr(Zp(5, print_mode='digits', show_prec=True)(6))
'...00000000000000000011'

sage: repr(Zp(5, print_mode='digits', show_prec='bigoh')(6))
'11 + O(5^20)'
print_pos, name and print_sep have no effect.

Equality depends on printing options:
sage: R == S, R == T, S == T
(False, False, False)

bars: elements are displayed as a string of base \(p\) digits with separators:

sage: R = Qp(5, print_mode='bars'); a = R(70700); repr(a)
'...4|2|3|0|3|0|0'
sage: b = R(-70700); repr(b)
'...4|4|4|4|4|4|4|4|4|4|4|4|4|4|4|0|2|1|4|2|0|0'
sage: d = R(-707/5^2); repr(d)
'...4|4|4|4|4|4|4|4|4|4|4|4|4|4|4|3|4|1|.|3|3'

Again, note that it’s not possible to read off the precision from the representation in this mode.

print_pos controls whether the digits can be negative.
sage: S = Qp(5, print_mode='bars',print_pos=False); b = S(-70700); repr(b)
'...-1|0|2|2|-1|2|0|0'
print_max_terms limits the number of digits that are printed. Note that if the valuation of the element is very negative, more digits will be printed.
sage: T = Qp(5, print_max_terms=4); T(-70700)
2*5^2 + 4*5^3 + 5^4 + 2*5^5 + ... + O(5^22)
sage: T(-707/5^2)
3*5^-2 + 3*5^-1 + 1 + 4*5 + ... + O(5^18)
sage: T(-707/5^6)
3*5^-6 + 3*5^-5 + 5^-4 + 4*5^-3 + ... + O(5^14)
sage: T(-707/5^6,absprec=-2)
3*5^-6 + 3*5^-5 + 5^-4 + 4*5^-3 + O(5^-2)
sage: T(-707/5^4)
3*5^-4 + 3*5^-3 + 5^-2 + 4*5^-1 + ... + O(5^16)
print_sep controls the separation character.
sage: U = Qp(5, print_mode='bars', print_sep=']['); a = U(70700); repr(a)
'...4][2][3][0][3][0][0'
show_prec determines how the precision is printed. It can be either ‘none’ (or equivalently False), ‘dots’ (or equivalently True) or ‘bigoh’ The default is False for the 'floating-point' type and True for all other types.
sage: repr(Qp(5, print_mode='bars', show_prec='bigoh')(6))
'...1|1 + O(5^20)'
name and print_alphabet have no effect.

Equality depends on printing options:
sage: R == S, R == T, R == U, S == T, S == U, T == U
(False, False, False, False, False, False)

EXAMPLES:

sage: K = Qp(15, check=False); a = K(999); a
9 + 6*15 + 4*15^2 + O(15^20)

create_key(p, prec=None, type='capped-rel', print_mode=None, names=None, ram_name=None, print_pos=None, print_sep=None, print_alphabet=None, print_max_terms=None, show_prec=None, check=True, label=None)#

Creates a key from input parameters for Qp.

See the documentation for Qp for more information.

create_object(version, key)#

Creates an object using a given key.

See the documentation for Qp for more information.

sage.rings.padics.factory.Qq(q, prec=None, type='capped-rel', modulus=None, names=None, print_mode=None, ram_name=None, res_name=None, print_pos=None, print_sep=None, print_max_ram_terms=None, print_max_unram_terms=None, print_max_terse_terms=None, show_prec=None, check=True, implementation='FLINT')#

Given a prime power \(q = p^n\), return the unique unramified extension of \(\QQ_p\) of degree \(n\).

INPUT:

q – integer, list, tuple or Factorization object. If q is an integer, it is the prime power \(q\) in \(\QQ_q\). If q is a Factorization object, it is the factorization of the prime power \(q\). As a tuple it is the pair (p, n), and as a list it is a single element list [(p, n)].
prec – integer (default: 20) the precision cap of the field. Individual elements keep track of their own precision. See TYPES and PRECISION below.
type – string (default: 'capped-rel') Valid types are 'capped-rel', 'floating-point', 'lattice-cap' and 'lattice-float'. See TYPES and PRECISION below
modulus – polynomial (default None) A polynomial defining an unramified extension of \(\QQ_p\). See MODULUS below.
names – string or tuple (None is only allowed when \(q=p\)). The name of the generator, reducing to a generator of the residue field.
print_mode – string (default: None). Valid modes are 'series', 'val-unit', 'terse', and 'bars'. See PRINTING below.
ram_name – string (defaults to string representation of \(p\) if None). ram_name controls how the prime is printed. See PRINTING below.
res_name – string (defaults to None, which corresponds to adding a '0' to the end of the name). Controls how elements of the residue field print.
print_pos – bool (default None) Whether to only use positive integers in the representations of elements. See PRINTING below.
print_sep – string (default None) The separator character used in the 'bars' mode. See PRINTING below.
print_max_ram_terms – integer (default None) The maximum number of powers of \(p\) shown. See PRINTING below.
print_max_unram_terms – integer (default None) The maximum number of entries shown in a coefficient of \(p\). See PRINTING below.
print_max_terse_terms – integer (default None) The maximum number of terms in the polynomial representation of an element (using 'terse'). See PRINTING below.
show_prec – bool (default None) whether to show the precision for elements. See PRINTING below.
check – bool (default True) whether to check inputs.

OUTPUT:

The corresponding unramified \(p\)-adic field.

TYPES AND PRECISION:

There are two types of precision for a \(p\)-adic element. The first is relative precision, which gives the number of known \(p\)-adic digits:

sage: R.<a> = Qq(25, 20, 'capped-rel', print_mode='series'); b = 25*a; b        # needs sage.libs.ntl
a*5^2 + O(5^22)
sage: b.precision_relative()                                                    # needs sage.libs.ntl
20

The second type of precision is absolute precision, which gives the power of \(p\) that this element is defined modulo:

sage: b.precision_absolute()                                                    # needs sage.libs.ntl
22

There are two types of unramified \(p\)-adic fields: capped relative fields, floating point fields.

sage: R.<a> = Qq(9, 5, 'capped-rel', print_mode='series'); b = (1+2*a)^4; b     # needs sage.libs.ntl
2 + (2*a + 2)*3 + (2*a + 1)*3^2 + O(3^5)
sage: c = R(3249); c                                                            # needs sage.libs.ntl
3^2 + 3^4 + 3^5 + 3^6 + O(3^7)
sage: b + c                                                                     # needs sage.libs.ntl
2 + (2*a + 2)*3 + (2*a + 2)*3^2 + 3^4 + O(3^5)

In the floating point case, elements do not track their precision, but the relative precision of elements is truncated during arithmetic to the precision cap of the field.

MODULUS:

The modulus needs to define an unramified extension of \(\QQ_p\): when it is reduced to a polynomial over \(\GF{p}\) it should be irreducible.

The modulus can be given in a number of forms.

A polynomial.

The base ring can be \(\ZZ\), \(\QQ\), \(\ZZ_p\), \(\QQ_p\), \(\GF{p}\).

sage: # needs sage.libs.ntl
sage: P.<x> = ZZ[]
sage: R.<a> = Qq(27, modulus = x^3 + 2*x + 1); R.modulus()
(1 + O(3^20))*x^3 + O(3^20)*x^2 + (2 + O(3^20))*x + 1 + O(3^20)
sage: P.<x> = QQ[]
sage: S.<a> = Qq(27, modulus = x^3 + 2*x + 1)
sage: P.<x> = Zp(3)[]
sage: T.<a> = Qq(27, modulus = x^3 + 2*x + 1)
sage: P.<x> = Qp(3)[]
sage: U.<a> = Qq(27, modulus = x^3 + 2*x + 1)
sage: P.<x> = GF(3)[]                                                           # needs sage.rings.finite_rings
sage: V.<a> = Qq(27, modulus = x^3 + 2*x + 1)

Which form the modulus is given in has no effect on the unramified extension produced:

sage: R == S, S == T, T == U, U == V                                            # needs sage.libs.ntl
(True, True, True, False)

unless the precision of the modulus differs. In the case of V, the modulus is only given to precision 1, so the resulting field has a precision cap of 1.

sage: # needs sage.libs.ntl
sage: V.precision_cap()
1
sage: U.precision_cap()
20
sage: P.<x> = Qp(3)[]
sage: modulus = x^3 + (2 + O(3^7))*x + (1 + O(3^10))
sage: modulus
(1 + O(3^20))*x^3 + (2 + O(3^7))*x + 1 + O(3^10)
sage: W.<a> = Qq(27, modulus = modulus); W.precision_cap()
7

The modulus can also be given as a symbolic expression.

sage: x = var('x')                                                              # needs sage.symbolic
sage: X.<a> = Qq(27, modulus = x^3 + 2*x + 1); X.modulus()                      # needs sage.symbolic
(1 + O(3^20))*x^3 + O(3^20)*x^2 + (2 + O(3^20))*x + 1 + O(3^20)
sage: X == R                                                                    # needs sage.libs.ntl sage.symbolic
True

By default, the polynomial chosen is the standard lift of the generator chosen for \(\GF{q}\).

sage: GF(125, 'a').modulus()                                                    # needs sage.rings.finite_rings
x^3 + 3*x + 3
sage: Y.<a> = Qq(125); Y.modulus()                                              # needs sage.libs.ntl
(1 + O(5^20))*x^3 + O(5^20)*x^2 + (3 + O(5^20))*x + 3 + O(5^20)

However, you can choose another polynomial if desired (as long as the reduction to \(\GF{p}[x]\) is irreducible).

sage: P.<x> = ZZ[]
sage: Z.<a> = Qq(125, modulus = x^3 + 3*x^2 + x + 1); Z.modulus()               # needs sage.libs.ntl
(1 + O(5^20))*x^3 + (3 + O(5^20))*x^2 + (1 + O(5^20))*x + 1 + O(5^20)
sage: Y == Z                                                                    # needs sage.libs.ntl
False

PRINTING:

There are many different ways to print \(p\)-adic elements. The way elements of a given field print is controlled by options passed in at the creation of the field. There are four basic printing modes ('series', 'val-unit', 'terse' and 'bars'; 'digits' is not available), as well as various options that either hide some information in the print representation or sometimes make print representations more compact. Note that the printing options affect whether different \(p\)-adic fields are considered equal.

series: elements are displayed as series in \(p\).

sage: R.<a> = Qq(9, 20, 'capped-rel', print_mode='series'); (1+2*a)^4           # needs sage.libs.ntl
2 + (2*a + 2)*3 + (2*a + 1)*3^2 + O(3^20)
sage: -3*(1+2*a)^4                                                              # needs sage.libs.ntl
3 + a*3^2 + 3^3 + (2*a + 2)*3^4 + (2*a + 2)*3^5 + (2*a + 2)*3^6 + (2*a + 2)*3^7
 + (2*a + 2)*3^8 + (2*a + 2)*3^9 + (2*a + 2)*3^10 + (2*a + 2)*3^11
 + (2*a + 2)*3^12 + (2*a + 2)*3^13 + (2*a + 2)*3^14 + (2*a + 2)*3^15
 + (2*a + 2)*3^16 + (2*a + 2)*3^17 + (2*a + 2)*3^18 + (2*a + 2)*3^19
 + (2*a + 2)*3^20 + O(3^21)
sage: ~(3*a+18)                                                                 # needs sage.libs.ntl
(a + 2)*3^-1 + 1 + 2*3 + (a + 1)*3^2 + 3^3 + 2*3^4 + (a + 1)*3^5 + 3^6 + 2*3^7
 + (a + 1)*3^8 + 3^9 + 2*3^10 + (a + 1)*3^11 + 3^12 + 2*3^13 + (a + 1)*3^14
 + 3^15 + 2*3^16 + (a + 1)*3^17 + 3^18 + O(3^19)

print_pos controls whether negatives can be used in the coefficients of powers of \(p\).

sage: S.<b> = Qq(9, print_mode='series', print_pos=False); (1+2*b)^4            # needs sage.libs.ntl
-1 - b*3 - 3^2 + (b + 1)*3^3 + O(3^20)
sage: -3*(1+2*b)^4                                                              # needs sage.libs.ntl
3 + b*3^2 + 3^3 + (-b - 1)*3^4 + O(3^21)

ram_name controls how the prime is printed.

sage: T.<d> = Qq(9, print_mode='series', ram_name='p'); 3*(1+2*d)^4             # needs sage.libs.ntl
2*p + (2*d + 2)*p^2 + (2*d + 1)*p^3 + O(p^21)

print_max_ram_terms limits the number of powers of \(p\) that appear.

sage: U.<e> = Qq(9, print_mode='series', print_max_ram_terms=4); repr(-3*(1+2*e)^4)         # needs sage.libs.ntl
'3 + e*3^2 + 3^3 + (2*e + 2)*3^4 + ... + O(3^21)'

print_max_unram_terms limits the number of terms that appear in a coefficient of a power of \(p\).

sage: # needs sage.libs.ntl
sage: V.<f> = Qq(128, prec = 8, print_mode='series'); repr((1+f)^9)
'(f^3 + 1) + (f^5 + f^4 + f^3 + f^2)*2 + (f^6 + f^5 + f^4 + f + 1)*2^2 + (f^5 + f^4 + f^2 + f + 1)*2^3 + (f^6 + f^5 + f^4 + f^3 + f^2 + f + 1)*2^4 + (f^5 + f^4)*2^5 + (f^6 + f^5 + f^4 + f^3 + f + 1)*2^6 + (f + 1)*2^7 + O(2^8)'
sage: V.<f> = Qq(128, prec = 8, print_mode='series', print_max_unram_terms = 3); repr((1+f)^9)
'(f^3 + 1) + (f^5 + f^4 + ... + f^2)*2 + (f^6 + f^5 + ... + 1)*2^2 + (f^5 + f^4 + ... + 1)*2^3 + (f^6 + f^5 + ... + 1)*2^4 + (f^5 + f^4)*2^5 + (f^6 + f^5 + ... + 1)*2^6 + (f + 1)*2^7 + O(2^8)'
sage: V.<f> = Qq(128, prec = 8, print_mode='series', print_max_unram_terms = 2); repr((1+f)^9)
'(f^3 + 1) + (f^5 + ... + f^2)*2 + (f^6 + ... + 1)*2^2 + (f^5 + ... + 1)*2^3 + (f^6 + ... + 1)*2^4 + (f^5 + f^4)*2^5 + (f^6 + ... + 1)*2^6 + (f + 1)*2^7 + O(2^8)'
sage: V.<f> = Qq(128, prec = 8, print_mode='series', print_max_unram_terms = 1); repr((1+f)^9)
'(f^3 + ...) + (f^5 + ...)*2 + (f^6 + ...)*2^2 + (f^5 + ...)*2^3 + (f^6 + ...)*2^4 + (f^5 + ...)*2^5 + (f^6 + ...)*2^6 + (f + ...)*2^7 + O(2^8)'
sage: V.<f> = Qq(128, prec = 8, print_mode='series', print_max_unram_terms = 0); repr((1+f)^9 - 1 - f^3)
'(...)*2 + (...)*2^2 + (...)*2^3 + (...)*2^4 + (...)*2^5 + (...)*2^6 + (...)*2^7 + O(2^8)'

show_prec determines how the precision is printed. It can be either ‘none’ (or equivalently False), ‘bigoh’ (or equivalently True). The default is False for the 'floating-point' type and True for all other types.

sage: U.<e> = Qq(9, 2, show_prec=False); repr(-3*(1+2*e)^4)                     # needs sage.libs.ntl
'3 + e*3^2'

print_sep and print_max_terse_terms have no effect.

Note that print options affect equality:

sage: R == S, R == T, R == U, R == V, S == T, S == U, S == V, T == U, T == V, U == V        # needs sage.libs.ntl
(False, False, False, False, False, False, False, False, False, False)

val-unit: elements are displayed as \(p^k u\):

sage: R.<a> = Qq(9, 7, print_mode='val-unit'); b = (1+3*a)^9 - 1; b             # needs sage.libs.ntl
3^3 * (15 + 64*a) + O(3^7)
sage: ~b                                                                        # needs sage.libs.ntl
3^-3 * (41 + a) + O(3)

print_pos controls whether to use a balanced representation or not.

sage: S.<a> = Qq(9, 7, print_mode='val-unit', print_pos=False)                  # needs sage.libs.ntl
sage: b = (1+3*a)^9 - 1; b                                                      # needs sage.libs.ntl
3^3 * (15 - 17*a) + O(3^7)
sage: ~b                                                                        # needs sage.libs.ntl
3^-3 * (-40 + a) + O(3)

ram_name affects how the prime is printed.

sage: # needs sage.libs.ntl
sage: A.<x> = Qp(next_prime(10^6), print_mode='val-unit')[]
sage: T.<a> = Qq(next_prime(10^6)^3, 4, print_mode='val-unit', ram_name='p',
....:            modulus=x^3+385831*x^2+106556*x+321036)
sage: b = ~(next_prime(10^6)^2*(a^2 + a - 4)); b
p^-2 * (503009563508519137754940 + 704413692798200940253892*a
         + 968097057817740999537581*a^2) + O(p^2)
sage: b * (a^2 + a - 4)
p^-2 * 1 + O(p^2)

print_max_terse_terms controls how many terms of the polynomial appear in the unit part.

sage: U.<a> = Qq(17^4, 6, print_mode='val-unit', print_max_terse_terms=3)       # needs sage.libs.ntl
sage: b = ~(17*(a^3-a+14)); b                                                   # needs sage.libs.ntl
17^-1 * (22110411 + 11317400*a + 20656972*a^2 + ...) + O(17^5)
sage: b*17*(a^3-a+14)                                                           # needs sage.libs.ntl
1 + O(17^6)

sage: U.<e> = Qq(9, 2, print_mode='val-unit', show_prec=False); repr(-3*(1+2*e)^4)          # needs sage.libs.ntl
'3 * (1 + 3*e)'

print_sep, print_max_ram_terms and print_max_unram_terms have no effect.

Equality again depends on the printing options:

sage: R == S, R == T, R == U, S == T, S == U, T == U                            # needs sage.libs.ntl
(False, False, False, False, False, False)

terse: elements are displayed as a polynomial of degree less than the degree of the extension.

sage: R.<a> = Qq(125, print_mode='terse')                                       # needs sage.libs.ntl
sage: (a+5)^177                                                                 # needs sage.libs.ntl
68210977979428 + 90313850704069*a + 73948093055069*a^2 + O(5^20)
sage: (a/5+1)^177                                                               # needs sage.libs.ntl
68210977979428/5^177 + 90313850704069/5^177*a + 73948093055069/5^177*a^2 + O(5^-157)

As of version 3.3, if coefficients of the polynomial are non-integral, they are always printed with an explicit power of \(p\) in the denominator.

sage: 5*a + a^2/25                                                              # needs sage.libs.ntl
5*a + 1/5^2*a^2 + O(5^18)

print_pos controls whether to use a balanced representation or not.

sage: (a-5)^6                                                                   # needs sage.libs.ntl
22864 + 95367431627998*a + 8349*a^2 + O(5^20)
sage: S.<a> = Qq(125, print_mode='terse', print_pos=False); b = (a-5)^6; b      # needs sage.libs.ntl
22864 - 12627*a + 8349*a^2 + O(5^20)
sage: (a - 1/5)^6                                                               # needs sage.libs.ntl
-20624/5^6 + 18369/5^5*a + 1353/5^3*a^2 + O(5^14)

ram_name affects how the prime is printed.

sage: T.<a> = Qq(125, print_mode='terse', ram_name='p'); (a - 1/5)^6            # needs sage.libs.ntl
95367431620001/p^6 + 18369/p^5*a + 1353/p^3*a^2 + O(p^14)

print_max_terse_terms controls how many terms of the polynomial are shown.

sage: U.<a> = Qq(625, print_mode='terse', print_max_terse_terms=2); (a-1/5)^6   # needs sage.libs.ntl
106251/5^6 + 49994/5^5*a + ... + O(5^14)

sage: U.<e> = Qq(9, 2, print_mode='terse', show_prec=False); repr(-3*(1+2*e)^4)             # needs sage.libs.ntl
'3 + 9*e'

print_sep, print_max_ram_terms and print_max_unram_terms have no effect.

Equality again depends on the printing options:

sage: R == S, R == T, R == U, S == T, S == U, T == U                            # needs sage.libs.ntl
(False, False, False, False, False, False)

digits: This print mode is not available when the residue field is not prime.

It might make sense to have a dictionary for small fields, but this isn’t implemented.

bars: elements are displayed in a similar fashion to series, but more compactly.

sage: R.<a> = Qq(125); (a+5)^6                                                  # needs sage.libs.ntl
(4*a^2 + 3*a + 4) + (3*a^2 + 2*a)*5 + (a^2 + a + 1)*5^2 + (3*a + 2)*5^3
 + (3*a^2 + a + 3)*5^4 + (2*a^2 + 3*a + 2)*5^5 + O(5^20)
sage: R.<a> = Qq(125, print_mode='bars', prec=8); repr((a+5)^6)                 # needs sage.libs.ntl
'...[2, 3, 2]|[3, 1, 3]|[2, 3]|[1, 1, 1]|[0, 2, 3]|[4, 3, 4]'
sage: repr((a-5)^6)                                                             # needs sage.libs.ntl
'...[0, 4]|[1, 4]|[2, 0, 2]|[1, 4, 3]|[2, 3, 1]|[4, 4, 3]|[2, 4, 4]|[4, 3, 4]'

Note that elements with negative valuation are shown with a decimal point at valuation 0.

sage: repr((a+1/5)^6)                                                           # needs sage.libs.ntl
'...[3]|[4, 1, 3]|.|[1, 2, 3]|[3, 3]|[0, 0, 3]|[0, 1]|[0, 1]|[1]'
sage: repr((a+1/5)^2)                                                           # needs sage.libs.ntl
'...[0, 0, 1]|.|[0, 2]|[1]'

If not enough precision is known, '?' is used instead.

sage: repr((a+R(1/5,relprec=3))^7)                                              # needs sage.libs.ntl
'...|.|?|?|?|?|[0, 1, 1]|[0, 2]|[1]'

Note that it’s not possible to read off the precision from the representation in this mode.

sage: # needs sage.libs.ntl
sage: b = a + 3; repr(b)
'...[3, 1]'
sage: c = a + R(3, 4); repr(c)
'...[3, 1]'
sage: b.precision_absolute()
8
sage: c.precision_absolute()
4

print_pos controls whether the digits can be negative.

sage: S.<a> = Qq(125, print_mode='bars', print_pos=False); repr((a-5)^6)        # needs sage.libs.ntl
'...[1, -1, 1]|[2, 1, -2]|[2, 0, -2]|[-2, -1, 2]|[0, 0, -1]|[-2]|[-1, -2, -1]'
sage: repr((a-1/5)^6)                                                           # needs sage.libs.ntl
'...[0, 1, 2]|[-1, 1, 1]|.|[-2, -1, -1]|[2, 2, 1]|[0, 0, -2]|[0, -1]|[0, -1]|[1]'

print_max_ram_terms controls the maximum number of “digits” shown. Note that this puts a cap on the relative precision, not the absolute precision.

sage: T.<a> = Qq(125, print_max_ram_terms=3, print_pos=False); (a-5)^6          # needs sage.libs.ntl
(-a^2 - 2*a - 1) - 2*5 - a^2*5^2 + ... + O(5^20)
sage: 5*(a-5)^6 + 50                                                            # needs sage.libs.ntl
(-a^2 - 2*a - 1)*5 - a^2*5^3 + (2*a^2 - a - 2)*5^4 + ... + O(5^21)

print_sep controls the separating character ('|' by default).

sage: U.<a> = Qq(625, print_mode='bars', print_sep=''); b = (a+5)^6; repr(b)    # needs sage.libs.ntl
'...[0, 1][4, 0, 2][3, 2, 2, 3][4, 2, 2, 4][0, 3][1, 1, 3][3, 1, 4, 1]'

print_max_unram_terms controls how many terms are shown in each “digit”:

sage: # needs sage.libs.ntl
sage: with local_print_mode(U, {'max_unram_terms': 3}): repr(b)
'...[0, 1][4,..., 0, 2][3,..., 2, 3][4,..., 2, 4][0, 3][1,..., 1, 3][3,..., 4, 1]'
sage: with local_print_mode(U, {'max_unram_terms': 2}): repr(b)
'...[0, 1][4,..., 2][3,..., 3][4,..., 4][0, 3][1,..., 3][3,..., 1]'
sage: with local_print_mode(U, {'max_unram_terms': 1}): repr(b)
'...[..., 1][..., 2][..., 3][..., 4][..., 3][..., 3][..., 1]'
sage: with local_print_mode(U, {'max_unram_terms':0}): repr(b-75*a)
'...[...][...][...][...][][...][...]'

show_prec determines how the precision is printed. It can be either ‘none’ (or equivalently False), ‘dots’ (or equivalently True) or ‘bigoh’ The default is False for the 'floating-point' type and True for all other types.

sage: U.<e> = Qq(9, 2, print_mode='bars', show_prec=True); repr(-3*(1+2*e)^4)   # needs sage.libs.ntl
'...[0, 1]|[1]|[]'

ram_name and print_max_terse_terms have no effect.

Equality depends on printing options:

sage: R == S, R == T, R == U, S == T, S == U, T == U                            # needs sage.libs.ntl
(False, False, False, False, False, False)

EXAMPLES:

Unlike for Qp, you can’t create Qq(N) when N is not a prime power.

However, you can use check=False to pass in a pair in order to not have to factor. If you do so, you need to use names explicitly rather than the R.<a> syntax.

sage: p = next_prime(2^123)
sage: k = Qp(p)
sage: R.<x> = k[]                                                               # needs sage.libs.ntl
sage: K = Qq([(p, 5)], modulus=x^5+x+4, names='a', ram_name='p',                # needs sage.libs.ntl
....:        print_pos=False, check=False)
sage: K.0^5                                                                     # needs sage.libs.ntl
(-a - 4) + O(p^20)

In tests on sage.math.washington.edu, the creation of K as above took an average of 1.58ms, while:

sage: K = Qq(p^5, modulus=x^5+x+4, names='a', ram_name='p',                     # needs sage.libs.ntl
....:        print_pos=False, check=True)

took an average of 24.5ms. Of course, with smaller primes these savings disappear.

sage.rings.padics.factory.QqCR(q, prec=None, *args, **kwds)#

A shortcut function to create capped relative unramified \(p\)-adic fields.

Same functionality as Qq(). See documentation for Qq() for a description of the input parameters.

EXAMPLES:

sage: R.<a> = QqCR(25, 40); R                                                   # needs sage.libs.ntl
5-adic Unramified Extension Field in a defined by x^2 + 4*x + 2

sage.rings.padics.factory.QqFP(q, prec=None, *args, **kwds)#

A shortcut function to create floating point unramified \(p\)-adic fields.

Same functionality as Qq(). See documentation for Qq() for a description of the input parameters.

EXAMPLES:

sage: R.<a> = QqFP(25, 40); R                                                   # needs sage.libs.flint
5-adic Unramified Extension Field in a defined by x^2 + 4*x + 2

sage.rings.padics.factory.ZpCA(p, prec=None, *args, **kwds)#

A shortcut function to create capped absolute \(p\)-adic rings.

See documentation for Zp() for a description of the input parameters.

EXAMPLES:

sage: ZpCA(5, 40)
5-adic Ring with capped absolute precision 40

sage.rings.padics.factory.ZpCR(p, prec=None, *args, **kwds)#

A shortcut function to create capped relative \(p\)-adic rings.

Same functionality as Zp(). See documentation for Zp() for a description of the input parameters.

EXAMPLES:

sage: ZpCR(5, 40)
5-adic Ring with capped relative precision 40

sage.rings.padics.factory.ZpER(p, prec=None, halt=None, secure=False, *args, **kwds)#

A shortcut function to create relaxed \(p\)-adic rings.

INPUT:

prec – an integer (default: 20), the default precision
halt – an integer (default: twice prec), the halting precision
secure – a boolean (default: False); if False, consider indistinguishable elements at the working precision as equal; otherwise, raise an error.

See documentation for Zp() for a description of the other input parameters.

A SHORT INTRODUCTION TO RELAXED \(p\)-ADICS:

The model for relaxed \(p\)-adics is quite different from any of the other types of \(p\)-adics. In addition to storing a finite approximation, one also stores a method for increasing the precision.

Relaxed \(p\)-adic rings are created by the constructor ZpER():

sage: R = ZpER(5, print_mode="digits"); R                                       # needs sage.libs.flint
5-adic Ring handled with relaxed arithmetics

The precision is not capped in \(R\):

sage: R.precision_cap()                                                         # needs sage.libs.flint
+Infinity

However, a default precision is fixed. This is the precision at which the elements will be printed:

sage: R.default_prec()                                                          # needs sage.libs.flint
20

A default halting precision is also set. It is the default absolute precision at which the elements will be compared. By default, it is twice the default precision:

sage: R.halting_prec()                                                          # needs sage.libs.flint
40

However, both the default precision and the halting precision can be customized at the creation of the parent as follows:

sage: S = ZpER(5, prec=10, halt=100)                                            # needs sage.libs.flint
sage: S.default_prec()                                                          # needs sage.libs.flint
10
sage: S.halting_prec()                                                          # needs sage.libs.flint
100

One creates elements as usual:

sage: a = R(17/42); a                                                           # needs sage.libs.flint
...00244200244200244201

sage: R.random_element()  # random                                              # needs sage.libs.flint
...21013213133412431402

Here we notice that 20 digits (that is the default precision) are printed. However, the computation model is designed in order to guarantee that more digits of \(a\) will be available on demand. This feature is reflected by the fact that, when we ask for the precision of \(a\), the software answers \(+\infty\):

sage: a.precision_absolute()                                                    # needs sage.libs.flint
+Infinity

Asking for more digits is achieved by the methods at_precision_absolute() and at_precision_relative():

sage: a.at_precision_absolute(30)                                               # needs sage.libs.flint
...?244200244200244200244200244201

As a shortcut, one can use the bracket operator:

sage: a[:30]                                                                    # needs sage.libs.flint
...?244200244200244200244200244201

Of course, standard operations are supported:

sage: # needs sage.libs.flint
sage: b = R(42/17)
sage: a + b
...03232011214322140002
sage: a - b
...42311334324023403400
sage: a * b
...00000000000000000001
sage: a / b
...12442142113021233401
sage: sqrt(a)
...20042333114021142101

We observe again that only 20 digits are printed but, as before, more digits are available on demand:

sage: sqrt(a)[:30]                                                              # needs sage.libs.flint
...?142443342120042333114021142101

Equality tests

Checking equalities between relaxed \(p\)-adics is a bit subtle and can sometimes be puzzling at first glance.

When the parent is created with secure=False (which is the default), elements are compared at the current precision, or at the default halting precision if it is higher:

sage: a == b                                                                    # needs sage.libs.flint
False

sage: a == sqrt(a)^2                                                            # needs sage.libs.flint
True
sage: a == sqrt(a)^2 + 5^50                                                     # needs sage.libs.flint
True

In the above example, the halting precision is \(40\); it is the reason why a congruence modulo \(5^50\) is considered as an equality. However, if both sides of the equalities have been previously computed with more digits, those digits are taken into account. Hence comparing two elements at different times can produce different results:

sage: # needs sage.libs.flint
sage: aa = sqrt(a)^2 + 5^50
sage: a == aa
True
sage: a[:60]
...?244200244200244200244200244200244200244200244200244200244201
sage: aa[:60]
...?244200244300244200244200244200244200244200244200244200244201
sage: a == aa
False

This annoying situation, where the output of a == aa may change depending on previous computations, cannot occur when the parent is created with secure=True. Indeed, in this case, if the equality cannot be decided, an error is raised:

sage: # needs sage.libs.flint
sage: S = ZpER(5, secure=True)
sage: u = S.random_element()
sage: uu = u + 5^50
sage: u == uu
Traceback (most recent call last):
...
PrecisionError: unable to decide equality; try to bound precision

sage: u[:60] == uu                                                              # needs sage.libs.flint
False

Self-referent numbers

A quite interesting feature with relaxed \(p\)-adics is the possibility to create (in some cases) self-referent numbers. Here is an example. We first declare a new variable as follows:

sage: x = R.unknown(); x                                                        # needs sage.libs.flint
...?.0

We then use the method set() to define \(x\) by writing down an equation it satisfies:

sage: x.set(1 + 5*x^2)                                                          # needs sage.libs.flint
True

The variable \(x\) now contains the unique solution of the equation \(x = 1 + 5 x^2\):

sage: x                                                                         # needs sage.libs.flint
...04222412141121000211

This works because the \(n\)-th digit of the right hand size of the defining equation only involves the \(i\)-th digits of \(x\) with \(i < n\) (this is due to the factor \(5\)).

As a comparison, the following does not work:

sage: # needs sage.libs.flint
sage: y = R.unknown()
sage: y.set(1 + 3*y^2)
True
sage: y
...?.0
sage: y[:20]
Traceback (most recent call last):
...
RecursionError: definition looks circular

Self-referent definitions also work with systems of equations:

sage: # needs sage.libs.flint
sage: u = R.unknown()
sage: v = R.unknown()
sage: w = R.unknown()
sage: u.set(1 + 2*v + 3*w^2 + 5*u*v*w)
True
sage: v.set(2 + 4*w + sqrt(1 + 5*u + 10*v + 15*w))
True
sage: w.set(3 + 25*(u*v + v*w + u*w))
True
sage: u
...31203130103131131433
sage: v
...33441043031103114240
sage: w
...30212422041102444403

sage.rings.padics.factory.ZpFM(p, prec=None, *args, **kwds)#

A shortcut function to create fixed modulus \(p\)-adic rings.

See documentation for Zp() for a description of the input parameters.

EXAMPLES:

sage: ZpFM(5, 40)
5-adic Ring of fixed modulus 5^40

sage.rings.padics.factory.ZpFP(p, prec=None, *args, **kwds)#

A shortcut function to create floating point \(p\)-adic rings.

Same functionality as Zp(). See documentation for Zp() for a description of the input parameters.

EXAMPLES:

sage: ZpFP(5, 40)
5-adic Ring with floating precision 40

sage.rings.padics.factory.ZpLC(p, prec=None, *args, **kwds)#

A shortcut function to create \(p\)-adic rings with lattice precision (precision is encoded by a lattice in a large vector space and tracked using automatic differentiation).

See documentation for Zp() for a description of the input parameters.

EXAMPLES:

Below is a small demo of the features by this model of precision:

sage: R = ZpLC(3, print_mode='terse')
sage: R
3-adic Ring with lattice-cap precision

sage: x = R(1,10)

Of course, when we multiply by 3, we gain one digit of absolute precision:

sage: 3*x
3 + O(3^11)

The lattice precision machinery sees this even if we decompose the computation into several steps:

sage: y = x+x
sage: y
2 + O(3^10)
sage: x + y
3 + O(3^11)

The same works for the multiplication:

sage: z = x^2
sage: z
1 + O(3^10)
sage: x*z
1 + O(3^11)

This can be more surprising when we are working with elements given at different precisions:

sage: R = ZpLC(2, print_mode='terse')
sage: x = R(1,10)
sage: y = R(1,5)
sage: z = x+y; z
2 + O(2^5)
sage: t = x-y; t
O(2^5)
sage: z+t  # observe that z+t = 2*x
2 + O(2^11)
sage: z-t  # observe that z-t = 2*y
2 + O(2^6)

sage: x = R(28888,15)
sage: y = R(204,10)
sage: z = x/y; z
242 + O(2^9)
sage: z*y  # which is x
28888 + O(2^15)

The SOMOS sequence is the sequence defined by the recurrence:

\[u_n = \frac {u_{n-1} u_{n-3} + u_{n-2}^2} {u_{n-4}}\]

It is known for its numerical instability. On the one hand, one can show that if the initial values are invertible in \(\ZZ_p\) and known at precision \(O(p^N)\) then all the next terms of the SOMOS sequence will be known at the same precision as well. On the other hand, because of the division, when we unroll the recurrence, we loose a lot of precision. Observe:

sage: R = Zp(2, 30, print_mode='terse')
sage: a,b,c,d = R(1,15), R(1,15), R(1,15), R(3,15)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
4 + O(2^15)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
13 + O(2^15)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
55 + O(2^15)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
21975 + O(2^15)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
6639 + O(2^13)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
7186 + O(2^13)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
569 + O(2^13)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
253 + O(2^13)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
4149 + O(2^13)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
2899 + O(2^12)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
3072 + O(2^12)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
349 + O(2^12)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
619 + O(2^12)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
243 + O(2^12)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
3 + O(2^2)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
2 + O(2^2)

If instead, we use the lattice precision, everything goes well:

sage: R = ZpLC(2, 30, print_mode='terse')
sage: a,b,c,d = R(1,15), R(1,15), R(1,15), R(3,15)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
4 + O(2^15)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
13 + O(2^15)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
55 + O(2^15)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
21975 + O(2^15)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
23023 + O(2^15)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
31762 + O(2^15)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
16953 + O(2^15)
sage: a,b,c,d = b,c,d,(b*d+c*c)/a; print(d)
16637 + O(2^15)

sage: for _ in range(100):
....:     a,b,c,d = b,c,d,(b*d+c*c)/a
sage: a
15519 + O(2^15)
sage: b
32042 + O(2^15)
sage: c
17769 + O(2^15)
sage: d
20949 + O(2^15)

ALGORITHM:

The precision is global. It is encoded by a lattice in a huge vector space whose dimension is the number of elements having this parent. Precision is tracked using automatic differentiation techniques (see [CRV2014] and [CRV2018]).

Concretely, this precision datum is an instance of the class sage.rings.padic.lattice_precision.PrecisionLattice. It is attached to the parent and is created at the same time as the parent. (It is actually a bit more subtle because two different parents may share the same instance; this happens for instance for a \(p\)-adic ring and its field of fractions.)

This precision datum is accessible through the method precision():

sage: R = ZpLC(5, print_mode='terse')
sage: prec = R.precision()
sage: prec
Precision lattice on 0 objects

This instance knows about all elements of the parent. It is automatically updated when a new element (of this parent) is created:

sage: x = R(3513,10)
sage: prec
Precision lattice on 1 object
sage: y = R(176,5)
sage: prec
Precision lattice on 2 objects
sage: z = R.random_element()
sage: prec
Precision lattice on 3 objects

The method tracked_elements() provides the list of all tracked elements:

sage: prec.tracked_elements()
[3513 + O(5^10), 176 + O(5^5), ...]

Similarly, when a variable is collected by the garbage collector, the precision lattice is updated. Note however that the update might be delayed. We can force it with the method del_elements():

sage: z = 0
sage: prec  # random output, could be 2 objects if the garbage collector is fast
Precision lattice on 3 objects
sage: prec.del_elements()
sage: prec
Precision lattice on 2 objects

The method precision_lattice() returns (a matrix defining) the lattice that models the precision. Here we have:

sage: prec.precision_lattice()                                                  # needs sage.geometry.polyhedron
[9765625       0]
[      0    3125]

Observe that \(5^10 = 9765625\) and \(5^5 = 3125\). The above matrix then reflects the precision on \(x\) and \(y\).

Now, observe how the precision lattice changes while performing computations:

sage: x, y = 3*x+2*y, 2*(x-y)
sage: prec.del_elements()
sage: prec.precision_lattice()                                                  # needs sage.geometry.polyhedron
[    3125 48825000]
[       0 48828125]

The matrix we get is no longer diagonal, meaning that some digits of precision are diffused among the two new elements \(x\) and \(y\). They nevertheless show up when we compute for instance \(x+y\):

sage: x
1516 + O(5^5)
sage: y
424 + O(5^5)
sage: x+y
17565 + O(5^11)

These diffused digits of precision (which are tracked but do not appear on the printing) allow to be always sharp on precision.

NOTE:

Each elementary operation requires significant manipulations on the precision lattice and therefore is costly. Precisely:

The creation of a new element has a cost \(O(n)\) where \(n\) is the number of tracked elements.
The destruction of one element has a cost \(O(m^2)\) where \(m\) is the distance between the destroyed element and the last one. Fortunately, it seems that \(m\) tends to be small in general (the dynamics of the list of tracked elements is rather close to that of a stack).

It is nevertheless still possible to manipulate several hundred variables (e.g. square matrices of size 5 or polynomials of degree 20).

The class PrecisionLattice provides several features for introspection, especially concerning timings. See history() and timings() for details.

See also

ZpLC()

class sage.rings.padics.factory.Zp_class#

Bases: UniqueFactory

A creation function for \(p\)-adic rings.

INPUT:

p – integer: the \(p\) in \(\ZZ_p\)
prec – integer (default: 20) the precision cap of the ring. In the lattice capped case, prec can either be a pair (relative_cap, absolute_cap) or an integer (understood as relative cap). In the relaxed case, prec can be either a pair (default_prec, halting_prec) or an integer (understood as default precision). Except for the fixed modulus and floating point cases, individual elements keep track of their own precision. See TYPES and PRECISION below.
type – string (default: 'capped-rel') Valid types are 'capped-rel', 'capped-abs', 'fixed-mod', 'floating-point', 'lattice-cap', 'lattice-float', 'relaxed'. See TYPES and PRECISION below.
print_mode – string (default: None). Valid modes are 'series', 'val-unit', 'terse', 'digits', and 'bars'. See PRINTING below.
names – string or tuple (defaults to a string representation of \(p\)). What to use whenever \(p\) is printed.
print_pos – bool (default None) Whether to only use positive integers in the representations of elements. See PRINTING below.
print_sep – string (default None) The separator character used in the 'bars' mode. See PRINTING below.
print_alphabet – tuple (default None) The encoding into digits for use in the 'digits' mode. See PRINTING below.
print_max_terms – integer (default None) The maximum number of terms shown. See PRINTING below.
show_prec – bool (default None) whether to show the precision for elements. See PRINTING below.
check – bool (default True) whether to check if \(p\) is prime. Non-prime input may cause seg-faults (but can also be useful for base \(n\) expansions for example)
label – string (default None) used for lattice precision to create parents with different lattices.

OUTPUT:

The corresponding \(p\)-adic ring.

TYPES AND PRECISION:

There are two main types of precision. The first is relative precision; it gives the number of known \(p\)-adic digits:

sage: R = Zp(5, 20, 'capped-rel', 'series'); a = R(675); a
2*5^2 + 5^4 + O(5^22)
sage: a.precision_relative()
20

The second type of precision is absolute precision, which gives the power of \(p\) that this element is defined modulo:

sage: a.precision_absolute()
22

There are several types of \(p\)-adic rings, depending on the methods used for tracking precision. Namely, we have:

capped relative rings (type='capped-rel')
capped absolute rings (type='capped-abs')
fixed modulus rings (type='fixed-mod')
floating point rings (type='floating-point')
lattice precision rings (type='lattice-cap' or type='lattice-float')
exact fields with relaxed arithmetics (type='relaxed')

sage: R = Zp(5, 5, 'capped-rel', 'series'); a = R(4006); a
1 + 5 + 2*5^3 + 5^4 + O(5^5)
sage: b = R(4025); b
5^2 + 2*5^3 + 5^4 + 5^5 + O(5^7)
sage: a + b
1 + 5 + 5^2 + 4*5^3 + 2*5^4 + O(5^5)

In the capped absolute type, instead of having a cap on the relative precision of an element there is instead a cap on the absolute precision. Elements still store their own precisions, and as with the capped relative case, exact elements are truncated when cast into the ring.

sage: R = Zp(5, 5, 'capped-abs', 'series'); a = R(4005); a
5 + 2*5^3 + 5^4 + O(5^5)
sage: b = R(4025); b
5^2 + 2*5^3 + 5^4 + O(5^5)
sage: a * b
5^3 + 2*5^4 + O(5^5)
sage: (a * b) // 5^3
1 + 2*5 + O(5^2)

The fixed modulus type is the leanest of the \(p\)-adic rings: it is basically just a wrapper around \(\ZZ / p^n \ZZ\) providing a unified interface with the rest of the \(p\)-adics. This is the type you should use if your sole interest is speed. It does not track precision of elements.

sage: R = Zp(5,5,'fixed-mod','series'); a = R(4005); a
5 + 2*5^3 + 5^4
sage: a // 5
1 + 2*5^2 + 5^3

The floating point case is similar to the fixed modulus type in that elements do not trac their own precision. However, relative precision is truncated with each operation rather than absolute precision.

On the contrary, the lattice type tracks precision using lattices and automatic differentiation. It is rather slow but provides sharp (often optimal) results regarding precision. We refer to the documentation of the function ZpLC() for a small demonstration of the capabilities of this precision model.

PRINTING:

There are many different ways to print \(p\)-adic elements. The way elements of a given ring print is controlled by options passed in at the creation of the ring. There are five basic printing modes ('series', 'val-unit', 'terse', 'digits' and 'bars'), as well as various options that either hide some information in the print representation or sometimes make print representations more compact. Note that the printing options affect whether different \(p\)-adic fields are considered equal.

series: elements are displayed as series in \(p\).

sage: R = Zp(5, print_mode='series'); a = R(70700); a
3*5^2 + 3*5^4 + 2*5^5 + 4*5^6 + O(5^22)
sage: b = R(-70700); b
2*5^2 + 4*5^3 + 5^4 + 2*5^5 + 4*5^7 + 4*5^8 + 4*5^9 + 4*5^10 + 4*5^11
 + 4*5^12 + 4*5^13 + 4*5^14 + 4*5^15 + 4*5^16 + 4*5^17 + 4*5^18
 + 4*5^19 + 4*5^20 + 4*5^21 + O(5^22)

print_pos controls whether negatives can be used in the coefficients of powers of \(p\).
sage: S = Zp(5, print_mode='series', print_pos=False); a = S(70700); a
-2*5^2 + 5^3 - 2*5^4 - 2*5^5 + 5^7 + O(5^22)
sage: b = S(-70700); b
2*5^2 - 5^3 + 2*5^4 + 2*5^5 - 5^7 + O(5^22)
print_max_terms limits the number of terms that appear.
sage: T = Zp(5, print_mode='series', print_max_terms=4); b = R(-70700); b
2*5^2 + 4*5^3 + 5^4 + 2*5^5 + ... + O(5^22)
names affects how the prime is printed.
sage: U.<p> = Zp(5); p
p + O(p^21)
show_prec determines how the precision is printed. It can be either ‘none’ (or equivalently False), ‘bigoh’ (or equivalently True). The default is False for the 'floating-point' and 'fixed-mod' types and True for all other types.
sage: Zp(5, show_prec=False)(6)
1 + 5
print_sep and print_alphabet have no effect.

Note that print options affect equality:
sage: R == S, R == T, R == U, S == T, S == U, T == U
(False, False, False, False, False, False)

val-unit: elements are displayed as \(p^k u\):

sage: R = Zp(5, print_mode='val-unit'); a = R(70700); a
5^2 * 2828 + O(5^22)
sage: b = R(-707*5); b
5 * 95367431639918 + O(5^21)

print_pos controls whether to use a balanced representation or not.
sage: S = Zp(5, print_mode='val-unit', print_pos=False); b = S(-70700); b
5^2 * (-2828) + O(5^22)
names affects how the prime is printed.
sage: T = Zp(5, print_mode='val-unit', names='pi'); a = T(70700); a
pi^2 * 2828 + O(pi^22)
show_prec determines how the precision is printed. It can be either ‘none’ (or equivalently False), ‘bigoh’ (or equivalently True). The default is False for the 'floating-point' and 'fixed-mod' types and True for all other types.
sage: Zp(5, print_mode='val-unit', show_prec=False)(30)
5 * 6
print_max_terms, print_sep and print_alphabet have no effect.

Equality again depends on the printing options:
sage: R == S, R == T, S == T
(False, False, False)

terse: elements are displayed as an integer in base 10:

sage: R = Zp(5, print_mode='terse'); a = R(70700); a
70700 + O(5^22)
sage: b = R(-70700); b
2384185790944925 + O(5^22)

print_pos controls whether to use a balanced representation or not.
sage: S = Zp(5, print_mode='terse', print_pos=False); b = S(-70700); b
-70700 + O(5^22)
name affects how the name is printed. Note that this interacts with the choice of shorter string for denominators.
sage: T.<unif> = Zp(5, print_mode='terse'); c = T(-707); c
95367431639918 + O(unif^20)
show_prec determines how the precision is printed. It can be either ‘none’ (or equivalently False), ‘bigoh’ (or equivalently True). The default is False for the 'floating-point' and 'fixed-mod' types and True for all other types.
sage: Zp(5, print_mode='terse', show_prec=False)(30)
30
print_max_terms, print_sep and print_alphabet have no effect.

Equality depends on printing options:
sage: R == S, R == T, S == T
(False, False, False)

digits: elements are displayed as a string of base \(p\) digits

Restriction: you can only use the digits printing mode for small primes. Namely, \(p\) must be less than the length of the alphabet tuple (default alphabet has length 62).
sage: R = Zp(5, print_mode='digits'); a = R(70700); repr(a)
'...4230300'
sage: b = R(-70700); repr(b)
'...4444444444444440214200'
Note that it’s not possible to read off the precision from the representation in this mode.

print_max_terms limits the number of digits that are printed.
sage: S = Zp(5, print_max_terms=4); S(-70700)
2*5^2 + 4*5^3 + 5^4 + 2*5^5 + ... + O(5^22)
print_alphabet controls the symbols used to substitute for digits greater than 9. Defaults to (‘0’, ‘1’, ‘2’, ‘3’, ‘4’, ‘5’, ‘6’, ‘7’, ‘8’, ‘9’, ‘A’, ‘B’, ‘C’, ‘D’, ‘E’, ‘F’, ‘G’, ‘H’, ‘I’, ‘J’, ‘K’, ‘L’, ‘M’, ‘N’, ‘O’, ‘P’, ‘Q’, ‘R’, ‘S’, ‘T’, ‘U’, ‘V’, ‘W’, ‘X’, ‘Y’, ‘Z’, ‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’, ‘g’, ‘h’, ‘i’, ‘j’, ‘k’, ‘l’, ‘m’, ‘n’, ‘o’, ‘p’, ‘q’, ‘r’, ‘s’, ‘t’, ‘u’, ‘v’, ‘w’, ‘x’, ‘y’, ‘z’):
sage: T = Zp(5, print_mode='digits', print_alphabet=('1','2','3','4','5'))
sage: repr(T(-70700))
'...5555555555555551325311'
show_prec determines how the precision is printed. It can be either 'none' (or equivalently False), 'dots' (or equivalently True) or 'bigoh'. The default is False for the 'floating-point' and 'fixed-mod' types and True for all other types.
sage: repr(Zp(5, 2, print_mode='digits', show_prec=True)(6))
'...11'
sage: repr(Zp(5, 2, print_mode='digits', show_prec='bigoh')(6))
'11 + O(5^2)'
print_pos, name and print_sep have no effect.

Equality depends on printing options:
sage: R == S, R == T, S == T
(False, False, False)

bars: elements are displayed as a string of base \(p\) digits with separators:

sage: R = Zp(5, print_mode='bars'); a = R(70700); repr(a)
'...4|2|3|0|3|0|0'
sage: b = R(-70700); repr(b)
'...4|4|4|4|4|4|4|4|4|4|4|4|4|4|4|0|2|1|4|2|0|0'

Again, note that it’s not possible to read off the precision from the representation in this mode.

print_pos controls whether the digits can be negative.
sage: S = Zp(5, print_mode='bars', print_pos=False); b = S(-70700); repr(b)
'...-1|0|2|2|-1|2|0|0'
print_max_terms limits the number of digits that are printed.
sage: T = Zp(5, print_max_terms=4); T(-70700)
2*5^2 + 4*5^3 + 5^4 + 2*5^5 + ... + O(5^22)
print_sep controls the separation character.
sage: U = Zp(5, print_mode='bars', print_sep=']['); a = U(70700); repr(a)
'...4][2][3][0][3][0][0'
show_prec determines how the precision is printed. It can be either ‘none’ (or equivalently False), ‘dots’ (or equivalently True) or ‘bigoh’. The default is False for the 'floating-point' and 'fixed-mod' types and True for all other types.
sage: repr(Zp(5, 2, print_mode='bars', show_prec=True)(6))
'...1|1'
sage: repr(Zp(5, 2, print_mode='bars', show_prec=False)(6))
'1|1'
name and print_alphabet have no effect.

Equality depends on printing options:
sage: R == S, R == T, R == U, S == T, S == U, T == U
(False, False, False, False, False, False)

EXAMPLES:

We allow non-prime \(p\), but only if check=False. Note that some features will not work.

sage: K = Zp(15, check=False); a = K(999); a
9 + 6*15 + 4*15^2 + O(15^20)

We create rings with various parameters:

sage: Zp(7)
7-adic Ring with capped relative precision 20
sage: Zp(9)
Traceback (most recent call last):
...
ValueError: p must be prime
sage: Zp(17, 5)
17-adic Ring with capped relative precision 5
sage: Zp(17, 5)(-1)
16 + 16*17 + 16*17^2 + 16*17^3 + 16*17^4 + O(17^5)

It works even with a fairly huge cap:

sage: Zp(next_prime(10^50), 100000)
100000000000000000000000000000000000000000000000151-adic Ring
 with capped relative precision 100000

We create each type of ring:

sage: Zp(7, 20, 'capped-rel')
7-adic Ring with capped relative precision 20
sage: Zp(7, 20, 'fixed-mod')
7-adic Ring of fixed modulus 7^20
sage: Zp(7, 20, 'capped-abs')
7-adic Ring with capped absolute precision 20

We create a capped relative ring with each print mode:

sage: k = Zp(7, 8, print_mode='series'); k
7-adic Ring with capped relative precision 8
sage: k(7*(19))
5*7 + 2*7^2 + O(7^9)
sage: k(7*(-19))
2*7 + 4*7^2 + 6*7^3 + 6*7^4 + 6*7^5 + 6*7^6 + 6*7^7 + 6*7^8 + O(7^9)

sage: k = Zp(7, print_mode='val-unit'); k
7-adic Ring with capped relative precision 20
sage: k(7*(19))
7 * 19 + O(7^21)
sage: k(7*(-19))
7 * 79792266297611982 + O(7^21)

sage: k = Zp(7, print_mode='terse'); k
7-adic Ring with capped relative precision 20
sage: k(7*(19))
133 + O(7^21)
sage: k(7*(-19))
558545864083283874 + O(7^21)

Note that \(p\)-adic rings are cached (via weak references):

sage: a = Zp(7); b = Zp(7)
sage: a is b
True

We create some elements in various rings:

sage: R = Zp(5); a = R(4); a
4 + O(5^20)
sage: S = Zp(5, 10, type = 'capped-abs'); b = S(2); b
2 + O(5^10)
sage: a + b
1 + 5 + O(5^10)

Creates a key from input parameters for Zp.

See the documentation for Zp() for more information.

create_object(version, key)#

Creates an object using a given key.

See the documentation for Zp() for more information.

sage.rings.padics.factory.Zq(q, prec=None, type='capped-rel', modulus=None, names=None, print_mode=None, ram_name=None, res_name=None, print_pos=None, print_sep=None, print_max_ram_terms=None, print_max_unram_terms=None, print_max_terse_terms=None, show_prec=None, check=True, implementation='FLINT')#

Given a prime power \(q = p^n\), return the unique unramified extension of \(\ZZ_p\) of degree \(n\).

INPUT:

q – integer, list or tuple: the prime power in \(\QQ_q\). Or a Factorization object, single element list [(p, n)] where p is a prime and n a positive integer, or the pair (p, n).
prec – integer (default: 20) the precision cap of the field. Individual elements keep track of their own precision. See TYPES and PRECISION below.
type – string (default: 'capped-rel') Valid types are 'capped-abs', 'capped-rel', 'fixed-mod', and 'floating-point'. See TYPES and PRECISION below.
modulus – polynomial (default None) A polynomial defining an unramified extension of \(\ZZ_p\). See MODULUS below.
names – string or tuple (None is only allowed when \(q=p\)). The name of the generator, reducing to a generator of the residue field.
print_mode – string (default: None). Valid modes are 'series', 'val-unit', 'terse', and 'bars'. See PRINTING below.
ram_name – string (defaults to string representation of \(p\) if None). ram_name controls how the prime is printed. See PRINTING below.
res_name – string (defaults to None, which corresponds to adding a '0' to the end of the name). Controls how elements of the residue field print.
print_pos – bool (default None) Whether to only use positive integers in the representations of elements. See PRINTING below.
print_sep – string (default None) The separator character used in the 'bars' mode. See PRINTING below.
print_max_ram_terms – integer (default None) The maximum number of powers of \(p\) shown. See PRINTING below.
print_max_unram_terms – integer (default None) The maximum number of entries shown in a coefficient of \(p\). See PRINTING below.
print_max_terse_terms – integer (default None) The maximum number of terms in the polynomial representation of an element (using 'terse'). See PRINTING below.
show_prec – bool (default None) Whether to show the precision for elements. See PRINTING below.
check – bool (default True) whether to check inputs.
implementation – string (default 'FLINT') which implementation to use. 'NTL' is the other option.

OUTPUT:

The corresponding unramified \(p\)-adic ring.

TYPES AND PRECISION:

There are two types of precision for a \(p\)-adic element. The first is relative precision (default), which gives the number of known \(p\)-adic digits:

sage: R.<a> = Zq(25, 20, 'capped-rel', print_mode='series'); b = 25*a; b        # needs sage.libs.ntl
a*5^2 + O(5^22)
sage: b.precision_relative()                                                    # needs sage.libs.ntl
20

The second type of precision is absolute precision, which gives the power of \(p\) that this element is defined modulo:

sage: b.precision_absolute()                                                    # needs sage.libs.ntl
22

There are many types of \(p\)-adic rings: capped relative rings (type='capped-rel'), capped absolute rings (type='capped-abs'), fixed modulus rings (type='fixed-mod'), and floating point rings (type='floating-point').

sage: R.<a> = Zq(9, 5, 'capped-rel', print_mode='series'); b = (1+2*a)^4; b     # needs sage.libs.ntl
2 + (2*a + 2)*3 + (2*a + 1)*3^2 + O(3^5)
sage: c = R(3249); c                                                            # needs sage.libs.ntl
3^2 + 3^4 + 3^5 + 3^6 + O(3^7)
sage: b + c                                                                     # needs sage.libs.ntl
2 + (2*a + 2)*3 + (2*a + 2)*3^2 + 3^4 + O(3^5)

One can invert non-units: the result is in the fraction field.

sage: d = ~(3*b+c); d                                                           # needs sage.libs.ntl
2*3^-1 + (a + 1) + (a + 1)*3 + a*3^3 + O(3^4)
sage: d.parent()                                                                # needs sage.libs.ntl
3-adic Unramified Extension Field in a defined by x^2 + 2*x + 2

The capped absolute case is the same as the capped relative case, except that the cap is on the absolute precision rather than the relative precision.

sage: # needs sage.libs.flint
sage: R.<a> = Zq(9, 5, 'capped-abs', print_mode='series'); b = 3*(1+2*a)^4; b
2*3 + (2*a + 2)*3^2 + (2*a + 1)*3^3 + O(3^5)
sage: c = R(3249); c                                                            # needs sage.libs.ntl
3^2 + 3^4 + O(3^5)
sage: b*c                                                                       # needs sage.libs.ntl
2*3^3 + (2*a + 2)*3^4 + O(3^5)
sage: b*c >> 1                                                                  # needs sage.libs.ntl
2*3^2 + (2*a + 2)*3^3 + O(3^4)

The fixed modulus case is like the capped absolute, except that individual elements don’t track their precision.

sage: # needs sage.libs.flint
sage: R.<a> = Zq(9, 5, 'fixed-mod', print_mode='series'); b = 3*(1+2*a)^4; b
2*3 + (2*a + 2)*3^2 + (2*a + 1)*3^3
sage: c = R(3249); c                                                            # needs sage.libs.ntl
3^2 + 3^4
sage: b*c                                                                       # needs sage.libs.ntl
2*3^3 + (2*a + 2)*3^4
sage: b*c >> 1                                                                  # needs sage.libs.ntl
2*3^2 + (2*a + 2)*3^3

MODULUS:

The modulus needs to define an unramified extension of \(\ZZ_p\): when it is reduced to a polynomial over \(\GF{p}\) it should be irreducible.

The modulus can be given in a number of forms.

A polynomial.

The base ring can be \(\ZZ\), \(\QQ\), \(\ZZ_p\), \(\GF{p}\), or anything that can be converted to \(\ZZ_p\).

sage: # needs sage.libs.ntl
sage: P.<x> = ZZ[]
sage: R.<a> = Zq(27, modulus = x^3 + 2*x + 1); R.modulus()
(1 + O(3^20))*x^3 + O(3^20)*x^2 + (2 + O(3^20))*x + 1 + O(3^20)
sage: P.<x> = QQ[]
sage: S.<a> = Zq(27, modulus = x^3 + 2/7*x + 1)
sage: P.<x> = Zp(3)[]
sage: T.<a> = Zq(27, modulus = x^3 + 2*x + 1)
sage: P.<x> = Qp(3)[]
sage: U.<a> = Zq(27, modulus = x^3 + 2*x + 1)
sage: P.<x> = GF(3)[]                                                           # needs sage.rings.finite_rings
sage: V.<a> = Zq(27, modulus = x^3 + 2*x + 1)

Which form the modulus is given in has no effect on the unramified extension produced:

sage: R == S, R == T, T == U, U == V                                            # needs sage.libs.ntl
(False, True, True, False)

unless the modulus is different, or the precision of the modulus differs. In the case of V, the modulus is only given to precision 1, so the resulting field has a precision cap of 1.

sage: # needs sage.libs.ntl
sage: V.precision_cap()
1
sage: U.precision_cap()
20
sage: P.<x> = Zp(3)[]
sage: modulus = x^3 + (2 + O(3^7))*x + (1 + O(3^10))
sage: modulus
(1 + O(3^20))*x^3 + (2 + O(3^7))*x + 1 + O(3^10)
sage: W.<a> = Zq(27, modulus = modulus); W.precision_cap()
7

The modulus can also be given as a symbolic expression.

sage: x = var('x')                                                              # needs sage.symbolic
sage: X.<a> = Zq(27, modulus = x^3 + 2*x + 1); X.modulus()                      # needs sage.symbolic
(1 + O(3^20))*x^3 + O(3^20)*x^2 + (2 + O(3^20))*x + 1 + O(3^20)
sage: X == R                                                                    # needs sage.libs.ntl sage.symbolic
True

By default, the polynomial chosen is the standard lift of the generator chosen for \(\GF{q}\).

sage: GF(125, 'a').modulus()                                                    # needs sage.rings.finite_rings
x^3 + 3*x + 3
sage: Y.<a> = Zq(125); Y.modulus()                                              # needs sage.libs.ntl
(1 + O(5^20))*x^3 + O(5^20)*x^2 + (3 + O(5^20))*x + 3 + O(5^20)

However, you can choose another polynomial if desired (as long as the reduction to \(\GF{p}[x]\) is irreducible).

sage: P.<x> = ZZ[]
sage: Z.<a> = Zq(125, modulus = x^3 + 3*x^2 + x + 1); Z.modulus()               # needs sage.libs.ntl
(1 + O(5^20))*x^3 + (3 + O(5^20))*x^2 + (1 + O(5^20))*x + 1 + O(5^20)
sage: Y == Z                                                                    # needs sage.libs.ntl
False

PRINTING:

series: elements are displayed as series in \(p\).

sage: # needs sage.libs.ntl
sage: R.<a> = Zq(9, 20, 'capped-rel', print_mode='series'); (1+2*a)^4
2 + (2*a + 2)*3 + (2*a + 1)*3^2 + O(3^20)
sage: -3*(1+2*a)^4
3 + a*3^2 + 3^3 + (2*a + 2)*3^4 + (2*a + 2)*3^5 + (2*a + 2)*3^6 + (2*a + 2)*3^7
  + (2*a + 2)*3^8 + (2*a + 2)*3^9 + (2*a + 2)*3^10 + (2*a + 2)*3^11 + (2*a + 2)*3^12
  + (2*a + 2)*3^13 + (2*a + 2)*3^14 + (2*a + 2)*3^15 + (2*a + 2)*3^16
  + (2*a + 2)*3^17 + (2*a + 2)*3^18 + (2*a + 2)*3^19 + (2*a + 2)*3^20 + O(3^21)
sage: b = ~(3*a+18); b
(a + 2)*3^-1 + 1 + 2*3 + (a + 1)*3^2 + 3^3 + 2*3^4 + (a + 1)*3^5 + 3^6 + 2*3^7
  + (a + 1)*3^8 + 3^9 + 2*3^10 + (a + 1)*3^11 + 3^12 + 2*3^13 + (a + 1)*3^14
  + 3^15 + 2*3^16 + (a + 1)*3^17 + 3^18 + O(3^19)
sage: b.parent() is R.fraction_field()
True

print_pos controls whether negatives can be used in the coefficients of powers of \(p\).

sage: S.<b> = Zq(9, print_mode='series', print_pos=False); (1+2*b)^4            # needs sage.libs.ntl
-1 - b*3 - 3^2 + (b + 1)*3^3 + O(3^20)
sage: -3*(1+2*b)^4                                                              # needs sage.libs.ntl
3 + b*3^2 + 3^3 + (-b - 1)*3^4 + O(3^21)

ram_name controls how the prime is printed.

sage: T.<d> = Zq(9, print_mode='series', ram_name='p'); 3*(1+2*d)^4             # needs sage.libs.ntl
2*p + (2*d + 2)*p^2 + (2*d + 1)*p^3 + O(p^21)

print_max_ram_terms limits the number of powers of \(p\) that appear.

sage: U.<e> = Zq(9, print_mode='series', print_max_ram_terms=4); repr(-3*(1+2*e)^4)         # needs sage.libs.ntl
'3 + e*3^2 + 3^3 + (2*e + 2)*3^4 + ... + O(3^21)'

print_max_unram_terms limits the number of terms that appear in a coefficient of a power of \(p\).

sage: # needs sage.libs.ntl
sage: V.<f> = Zq(128, prec = 8, print_mode='series'); repr((1+f)^9)
'(f^3 + 1) + (f^5 + f^4 + f^3 + f^2)*2 + (f^6 + f^5 + f^4 + f + 1)*2^2 + (f^5 + f^4 + f^2 + f + 1)*2^3 + (f^6 + f^5 + f^4 + f^3 + f^2 + f + 1)*2^4 + (f^5 + f^4)*2^5 + (f^6 + f^5 + f^4 + f^3 + f + 1)*2^6 + (f + 1)*2^7 + O(2^8)'
sage: V.<f> = Zq(128, prec = 8, print_mode='series', print_max_unram_terms = 3); repr((1+f)^9)
'(f^3 + 1) + (f^5 + f^4 + ... + f^2)*2 + (f^6 + f^5 + ... + 1)*2^2 + (f^5 + f^4 + ... + 1)*2^3 + (f^6 + f^5 + ... + 1)*2^4 + (f^5 + f^4)*2^5 + (f^6 + f^5 + ... + 1)*2^6 + (f + 1)*2^7 + O(2^8)'
sage: V.<f> = Zq(128, prec = 8, print_mode='series', print_max_unram_terms = 2); repr((1+f)^9)
'(f^3 + 1) + (f^5 + ... + f^2)*2 + (f^6 + ... + 1)*2^2 + (f^5 + ... + 1)*2^3 + (f^6 + ... + 1)*2^4 + (f^5 + f^4)*2^5 + (f^6 + ... + 1)*2^6 + (f + 1)*2^7 + O(2^8)'
sage: V.<f> = Zq(128, prec = 8, print_mode='series', print_max_unram_terms = 1); repr((1+f)^9)
'(f^3 + ...) + (f^5 + ...)*2 + (f^6 + ...)*2^2 + (f^5 + ...)*2^3 + (f^6 + ...)*2^4 + (f^5 + ...)*2^5 + (f^6 + ...)*2^6 + (f + ...)*2^7 + O(2^8)'
sage: V.<f> = Zq(128, prec = 8, print_mode='series', print_max_unram_terms = 0); repr((1+f)^9 - 1 - f^3)
'(...)*2 + (...)*2^2 + (...)*2^3 + (...)*2^4 + (...)*2^5 + (...)*2^6 + (...)*2^7 + O(2^8)'

show_prec determines how the precision is printed. It can be either 'none' (or equivalently False), 'bigoh' (or equivalently True). The default is False for the 'floating-point' and 'fixed-mod' types and True for all other types.

sage: U.<e> = Zq(9, 2, show_prec=False); repr(-3*(1+2*e)^4)                     # needs sage.libs.ntl
'3 + e*3^2'

print_sep and print_max_terse_terms have no effect.

Note that print options affect equality:

sage: R == S, R == T, R == U, R == V, S == T, S == U, S == V, T == U, T == V, U == V        # needs sage.libs.ntl
(False, False, False, False, False, False, False, False, False, False)

val-unit: elements are displayed as \(p^k u\):

sage: R.<a> = Zq(9, 7, print_mode='val-unit'); b = (1+3*a)^9 - 1; b             # needs sage.libs.ntl
3^3 * (15 + 64*a) + O(3^7)
sage: ~b                                                                        # needs sage.libs.ntl
3^-3 * (41 + a) + O(3)

print_pos controls whether to use a balanced representation or not.

sage: S.<a> = Zq(9, 7, print_mode='val-unit', print_pos=False); b = (1+3*a)^9 - 1; b        # needs sage.libs.ntl
3^3 * (15 - 17*a) + O(3^7)
sage: ~b                                                                                    # needs sage.libs.ntl
3^-3 * (-40 + a) + O(3)

ram_name affects how the prime is printed.

sage: # needs sage.libs.ntl
sage: A.<x> = Zp(next_prime(10^6), print_mode='val-unit')[]
sage: T.<a> = Zq(next_prime(10^6)^3, 4, print_mode='val-unit', ram_name='p',
....:            modulus=x^3+385831*x^2+106556*x+321036)
sage: b = next_prime(10^6)^2*(a^2 + a - 4)^4; b
p^2 * (87996187118837557387483 + 246348888344392418464080*a + 1353538653775332610349*a^2)
 + O(p^6)
sage: b * (a^2 + a - 4)^-4
p^2 * 1 + O(p^6)

print_max_terse_terms controls how many terms of the polynomial appear in the unit part.

sage: # needs sage.libs.ntl
sage: U.<a> = Zq(17^4, 6, print_mode='val-unit', print_max_terse_terms=3)
sage: b = 17*(a^3-a+14)^6; b
17 * (12131797 + 12076378*a + 10809706*a^2 + ...) + O(17^7)

sage: U.<e> = Zq(9, 2, print_mode='val-unit', show_prec=False); repr(-3*(1+2*e)^4)          # needs sage.libs.ntl
'3 * (1 + 3*e)'

print_sep, print_max_ram_terms and print_max_unram_terms have no effect.

Equality again depends on the printing options:

sage: R == S, R == T, R == U, S == T, S == U, T == U                            # needs sage.libs.ntl
(False, False, False, False, False, False)

terse: elements are displayed as a polynomial of degree less than the degree of the extension.

sage: # needs sage.libs.ntl
sage: R.<a> = Zq(125, print_mode='terse')
sage: (a+5)^177
68210977979428 + 90313850704069*a + 73948093055069*a^2 + O(5^20)
sage: (a/5+1)^177
68210977979428/5^177 + 90313850704069/5^177*a + 73948093055069/5^177*a^2 + O(5^-157)

Note that in this last computation, you get one fewer \(p\)-adic digit than one might expect. This is because R is capped absolute, and thus 5 is cast in with relative precision 19.

As of version 3.3, if coefficients of the polynomial are non-integral, they are always printed with an explicit power of \(p\) in the denominator.
sage: # needs sage.libs.ntl
sage: 5*a + a^2/25
5*a + 1/5^2*a^2 + O(5^18)
print_pos controls whether to use a balanced representation or not.
sage: # needs sage.libs.ntl
sage: (a-5)^6
22864 + 95367431627998*a + 8349*a^2 + O(5^20)
sage: S.<a> = Zq(125, print_mode='terse', print_pos=False); b = (a-5)^6; b
22864 - 12627*a + 8349*a^2 + O(5^20)
sage: (a - 1/5)^6
-20624/5^6 + 18369/5^5*a + 1353/5^3*a^2 + O(5^14)
ram_name affects how the prime is printed.
sage: T.<a> = Zq(125, print_mode='terse', ram_name='p'); (a - 1/5)^6            # needs sage.libs.ntl
95367431620001/p^6 + 18369/p^5*a + 1353/p^3*a^2 + O(p^14)
print_max_terse_terms controls how many terms of the polynomial are shown.
sage: U.<a> = Zq(625, print_mode='terse', print_max_terse_terms=2); (a-1/5)^6   # needs sage.libs.ntl
106251/5^6 + 49994/5^5*a + ... + O(5^14)
show_prec determines how the precision is printed. It can be either 'none' (or equivalently False), 'bigoh' (or equivalently True). The default is False for the 'floating-point' and 'fixed-mod' types and True for all other types.
sage: U.<e> = Zq(9, 2, print_mode='terse', show_prec=False); repr(-3*(1+2*e)^4)             # needs sage.libs.ntl
'3 + 9*e'
print_sep, print_max_ram_terms and print_max_unram_terms have no effect.

Equality again depends on the printing options:
sage: R == S, R == T, R == U, S == T, S == U, T == U                            # needs sage.libs.ntl
(False, False, False, False, False, False)

digits: This print mode is not available when the residue field is not prime. It might make sense to have a dictionary for small fields, but this isn’t implemented.

bars: elements are displayed in a similar fashion to series, but more compactly.

sage: # needs sage.libs.ntl
sage: R.<a> = Zq(125); (a+5)^6
(4*a^2 + 3*a + 4) + (3*a^2 + 2*a)*5 + (a^2 + a + 1)*5^2 + (3*a + 2)*5^3
 + (3*a^2 + a + 3)*5^4 + (2*a^2 + 3*a + 2)*5^5 + O(5^20)
sage: R.<a> = Zq(125, print_mode='bars', prec=8); repr((a+5)^6)
'...[2, 3, 2]|[3, 1, 3]|[2, 3]|[1, 1, 1]|[0, 2, 3]|[4, 3, 4]'
sage: repr((a-5)^6)
'...[0, 4]|[1, 4]|[2, 0, 2]|[1, 4, 3]|[2, 3, 1]|[4, 4, 3]|[2, 4, 4]|[4, 3, 4]'

Note that it’s not possible to read off the precision from the representation in this mode.

sage: # needs sage.libs.ntl
sage: b = a + 3; repr(b)
'...[3, 1]'
sage: c = a + R(3, 4); repr(c)
'...[3, 1]'
sage: b.precision_absolute()
8
sage: c.precision_absolute()
4

print_pos controls whether the digits can be negative.

sage: # needs sage.libs.ntl
sage: S.<a> = Zq(125, print_mode='bars', print_pos=False); repr((a-5)^6)
'...[1, -1, 1]|[2, 1, -2]|[2, 0, -2]|[-2, -1, 2]|[0, 0, -1]|[-2]|[-1, -2, -1]'
sage: repr((a-1/5)^6)
'...[0, 1, 2]|[-1, 1, 1]|.|[-2, -1, -1]|[2, 2, 1]|[0, 0, -2]|[0, -1]|[0, -1]|[1]'

print_max_ram_terms controls the maximum number of “digits” shown. Note that this puts a cap on the relative precision, not the absolute precision.

sage: # needs sage.libs.ntl
sage: T.<a> = Zq(125, print_max_ram_terms=3, print_pos=False); (a-5)^6
(-a^2 - 2*a - 1) - 2*5 - a^2*5^2 + ... + O(5^20)
sage: 5*(a-5)^6 + 50
(-a^2 - 2*a - 1)*5 - a^2*5^3 + (2*a^2 - a - 2)*5^4 + ... + O(5^21)
sage: (a-1/5)^6
5^-6 - a*5^-5 - a*5^-4 + ... + O(5^14)

print_sep controls the separating character ('|' by default).

sage: U.<a> = Zq(625, print_mode='bars', print_sep=''); b = (a+5)^6; repr(b)    # needs sage.libs.ntl
'...[0, 1][4, 0, 2][3, 2, 2, 3][4, 2, 2, 4][0, 3][1, 1, 3][3, 1, 4, 1]'

print_max_unram_terms controls how many terms are shown in each 'digit':

sage: # needs sage.libs.ntl
sage: with local_print_mode(U, {'max_unram_terms': 3}): repr(b)
'...[0, 1][4,..., 0, 2][3,..., 2, 3][4,..., 2, 4][0, 3][1,..., 1, 3][3,..., 4, 1]'
sage: with local_print_mode(U, {'max_unram_terms': 2}): repr(b)
'...[0, 1][4,..., 2][3,..., 3][4,..., 4][0, 3][1,..., 3][3,..., 1]'
sage: with local_print_mode(U, {'max_unram_terms': 1}): repr(b)
'...[..., 1][..., 2][..., 3][..., 4][..., 3][..., 3][..., 1]'
sage: with local_print_mode(U, {'max_unram_terms':0}): repr(b-75*a)
'...[...][...][...][...][][...][...]'

show_prec determines how the precision is printed. It can be either 'none' (or equivalently False), 'dots' (or equivalently True) or 'bigoh'. The default is False for the 'floating-point' and 'fixed-mod' types and True for all other types.

sage: U.<e> = Zq(9, 2, print_mode='bars', show_prec='bigoh'); repr(-3*(1+2*e)^4)            # needs sage.libs.ntl
'[0, 1]|[1]|[] + O(3^3)'

ram_name and print_max_terse_terms have no effect.

Equality depends on printing options:

sage: R == S, R == T, R == U, S == T, S == U, T == U                            # needs sage.libs.ntl
(False, False, False, False, False, False)

EXAMPLES:

Unlike for Zp(), you can’t create Zq(N) when N is not a prime power.

However, you can use check=False to pass in a pair in order to not have to factor. If you do so, you need to use names explicitly rather than the R.<a> syntax.

sage: # needs sage.libs.ntl
sage: p = next_prime(2^123)
sage: k = Zp(p)
sage: R.<x> = k[]
sage: K = Zq([(p, 5)], modulus=x^5+x+4, names='a', ram_name='p',
....:        print_pos=False, check=False)
sage: K.0^5
(-a - 4) + O(p^20)

In tests on sage.math, the creation of K as above took an average of 1.58ms, while:

sage: K = Zq(p^5, modulus=x^5+x+4, names='a', ram_name='p',                     # needs sage.libs.ntl
....:        print_pos=False, check=True)

took an average of 24.5ms. Of course, with smaller primes these savings disappear.

sage.rings.padics.factory.ZqCA(q, prec=None, *args, **kwds)#

A shortcut function to create capped absolute unramified \(p\)-adic rings.

See documentation for Zq() for a description of the input parameters.

EXAMPLES:

sage: R.<a> = ZqCA(25, 40); R                                                   # needs sage.libs.flint
5-adic Unramified Extension Ring in a defined by x^2 + 4*x + 2

sage.rings.padics.factory.ZqCR(q, prec=None, *args, **kwds)#

A shortcut function to create capped relative unramified \(p\)-adic rings.

Same functionality as Zq(). See documentation for Zq() for a description of the input parameters.

EXAMPLES:

sage: R.<a> = ZqCR(25, 40); R                                                   # needs sage.libs.ntl
5-adic Unramified Extension Ring in a defined by x^2 + 4*x + 2

sage.rings.padics.factory.ZqFM(q, prec=None, *args, **kwds)#

A shortcut function to create fixed modulus unramified \(p\)-adic rings.

See documentation for Zq() for a description of the input parameters.

EXAMPLES:

sage: R.<a> = ZqFM(25, 40); R                                                   # needs sage.libs.flint
5-adic Unramified Extension Ring in a defined by x^2 + 4*x + 2

sage.rings.padics.factory.ZqFP(q, prec=None, *args, **kwds)#

A shortcut function to create floating point unramified \(p\)-adic rings.

Same functionality as Zq(). See documentation for Zq() for a description of the input parameters.

EXAMPLES:

sage: R.<a> = ZqFP(25, 40); R                                                   # needs sage.libs.flint
5-adic Unramified Extension Ring in a defined by x^2 + 4*x + 2

sage.rings.padics.factory.get_key_base(p, prec, type, print_mode, names, ram_name, print_pos, print_sep, print_alphabet, print_max_terms, show_prec, check, valid_types, label=None)#

This implements create_key for Zp and Qp: moving it here prevents code duplication.

It fills in unspecified values and checks for contradictions in the input. It also standardizes irrelevant options so that duplicate parents are not created.

EXAMPLES:

sage: from sage.rings.padics.factory import get_key_base
sage: get_key_base(11, 5, 'capped-rel', None, None, None, None, ':', None, None, False, True, ['capped-rel'])
(11, 5, 'capped-rel', 'series', '11', True, '|', (), -1, 'none', None)
sage: get_key_base(12, 5, 'capped-rel', 'digits', None, None, None, None, None, None, True, False, ['capped-rel'])
(12,
 5,
 'capped-rel',
 'digits',
 '12',
 True,
 '|',
 ('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B'),
 -1,
 'dots',
 None)

sage.rings.padics.factory.is_eisenstein(poly)#

Return True iff this monic polynomial is Eisenstein.

A polynomial is Eisenstein if it is monic, the constant term has valuation 1 and all other terms have positive valuation.

EXAMPLES:

sage: # needs sage.libs.ntl
sage: R = Zp(5)
sage: S.<x> = R[]
sage: from sage.rings.padics.factory import is_eisenstein
sage: f = x^4 - 75*x + 15
sage: is_eisenstein(f)
True
sage: g = x^4 + 75
sage: is_eisenstein(g)
False
sage: h = x^7 + 27*x -15
sage: is_eisenstein(h)
False

sage.rings.padics.factory.is_unramified(poly)#

Return True iff this monic polynomial is unramified.

A polynomial is unramified if its reduction modulo the maximal ideal is irreducible.

EXAMPLES:

sage: # needs sage.libs.ntl
sage: R = Zp(5)
sage: S.<x> = R[]
sage: from sage.rings.padics.factory import is_unramified
sage: f = x^4 + 14*x + 9
sage: is_unramified(f)
True
sage: g = x^6 + 17*x + 6
sage: is_unramified(g)
False

sage.rings.padics.factory.krasner_check(poly, prec)#

Return True iff poly determines a unique isomorphism class of extensions at precision prec.

Currently just returns True (thus allowing extensions that are not defined to high enough precision in order to specify them up to isomorphism). This will change in the future.

EXAMPLES:

sage: from sage.rings.padics.factory import krasner_check
sage: krasner_check(1,2)  # this is a stupid example.
True

class sage.rings.padics.factory.pAdicExtension_class#

Bases: UniqueFactory

A class for creating extensions of \(p\)-adic rings and fields.

EXAMPLES:

sage: R = Zp(5,3)
sage: S.<x> = ZZ[]
sage: W.<w> = pAdicExtension(R, x^4 - 15); W                                    # needs sage.libs.ntl
5-adic Eisenstein Extension Ring in w defined by x^4 - 15
sage: W.precision_cap()                                                         # needs sage.libs.ntl
12

create_key_and_extra_args(base, modulus, prec=None, print_mode=None, names=None, var_name=None, res_name=None, unram_name=None, ram_name=None, print_pos=None, print_sep=None, print_alphabet=None, print_max_ram_terms=None, print_max_unram_terms=None, print_max_terse_terms=None, show_prec=None, check=True, unram=False, implementation='FLINT')#

Creates a key from input parameters for pAdicExtension.

See the documentation for Qq() for more information.

create_object(version, key, approx_modulus=None, shift_seed=None)#

Creates an object using a given key.

See the documentation for pAdicExtension for more information.

sage.rings.padics.factory.split(poly, prec)#

Given a polynomial poly and a desired precision prec, computes upoly and epoly so that the extension defined by poly is isomorphic to the extension defined by first taking an extension by the unramified polynomial upoly, and then an extension by the Eisenstein polynomial epoly.

We need better \(p\)-adic factoring in Sage before this function can be implemented.

EXAMPLES:

sage: k = Qp(13)
sage: x = polygen(k)                                                            # needs sage.libs.ntl
sage: f = x^2 + 1                                                               # needs sage.libs.ntl
sage: sage.rings.padics.factory.split(f, 10)                                    # needs sage.libs.ntl sage.rings.real_double
Traceback (most recent call last):
...
NotImplementedError: Extensions by general polynomials not yet supported.
Please use an unramified or Eisenstein polynomial.

sage.rings.padics.factory.truncate_to_prec(poly, R, absprec)#

Truncates the unused precision off of a polynomial.

EXAMPLES:

sage: R = Zp(5)
sage: S.<x> = R[]                                                               # needs sage.libs.ntl
sage: from sage.rings.padics.factory import truncate_to_prec
sage: f = x^4 + (3+O(5^6))*x^3 + O(5^4)                                         # needs sage.libs.ntl
sage: truncate_to_prec(f, R, 5)                                                 # needs sage.libs.ntl
(1 + O(5^5))*x^4 + (3 + O(5^5))*x^3 + O(5^5)*x^2 + O(5^5)*x + O(5^4)