# Asymptotics of Multivariate Generating Series¶

Let $$F(x) = \sum_{\nu \in \NN^d} F_{\nu} x^\nu$$ be a multivariate power series with complex coefficients that converges in a neighborhood of the origin. Assume that $$F = G/H$$ for some functions $$G$$ and $$H$$ holomorphic in a neighborhood of the origin. Assume also that $$H$$ is a polynomial.

This computes asymptotics for the coefficients $$F_{r \alpha}$$ as $$r \to \infty$$ with $$r \alpha \in \NN^d$$ for $$\alpha$$ in a permissible subset of $$d$$-tuples of positive reals. More specifically, it computes arbitrary terms of the asymptotic expansion for $$F_{r \alpha}$$ when the asymptotics are controlled by a strictly minimal multiple point of the algebraic variety $$H = 0$$.

The algorithms and formulas implemented here come from [RW2008] and [RW2012]. For a general reference take a look in the book [PW2013].

## Introductory Examples¶

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing


A univariate smooth point example:

sage: R.<x> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: H = (x - 1/2)^3
sage: Hfac = H.factor()
sage: G = -1/(x + 3)/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: F
(-1/(x + 3), [(x - 1/2, 3)])
sage: alpha = [1]
sage: decomp = F.asymptotic_decomposition(alpha)
sage: decomp
(0, []) +
(-1/2*r^2*(x^2/(x^5 + 9*x^4 + 27*x^3 + 27*x^2)
+ 6*x/(x^5 + 9*x^4 + 27*x^3 + 27*x^2)
+ 9/(x^5 + 9*x^4 + 27*x^3 + 27*x^2))
- 1/2*r*(5*x^2/(x^5 + 9*x^4 + 27*x^3 + 27*x^2)
+ 24*x/(x^5 + 9*x^4 + 27*x^3 + 27*x^2)
+ 27/(x^5 + 9*x^4 + 27*x^3 + 27*x^2))
- 3*x^2/(x^5 + 9*x^4 + 27*x^3 + 27*x^2)
- 9*x/(x^5 + 9*x^4 + 27*x^3 + 27*x^2)
- 9/(x^5 + 9*x^4 + 27*x^3 + 27*x^2),
[(x - 1/2, 1)])
sage: F1 = decomp[1]
sage: p = {x: 1/2}
sage: asy = F1.asymptotics(p, alpha, 3)
sage: asy
(8/343*(49*r^2 + 161*r + 114)*2^r, 2, 8/7*r^2 + 184/49*r + 912/343)
sage: F.relative_error(asy[0], alpha, [1, 2, 4, 8, 16], asy[1])
[((1,), 7.555555556, [7.556851312], [-0.0001714971672]),
((2,), 14.74074074, [14.74052478], [0.00001465051901]),
((4,), 35.96502058, [35.96501458], [1.667911934e-7]),
((8,), 105.8425656, [105.8425656], [4.399565380e-11]),
((16,), 355.3119534, [355.3119534], [0.0000000000])]


Another smooth point example (Example 5.4 of [RW2008]):

sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: q = 1/2
sage: qq = q.denominator()
sage: H = 1 - q*x + q*x*y - x^2*y
sage: Hfac = H.factor()
sage: G = (1 - q*x)/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: alpha = list(qq*vector([2, 1 - q]))
sage: alpha
[4, 1]
sage: I = F.smooth_critical_ideal(alpha)
sage: I
Ideal (y^2 - 2*y + 1, x + 1/4*y - 5/4) of
Multivariate Polynomial Ring in x, y over Rational Field
sage: s = solve([SR(z) for z in I.gens()],
....:           [SR(z) for z in R.gens()], solution_dict=true)
sage: s == [{SR(x): 1, SR(y): 1}]
True
sage: p = s[0]
sage: asy = F.asymptotics(p, alpha, 1, verbose=True)
Creating auxiliary functions...
Computing derivatives of auxiliary functions...
Computing derivatives of more auxiliary functions...
Computing second order differential operator actions...
sage: asy
(1/24*2^(2/3)*(sqrt(3) + 4/(sqrt(3) + I) + I)*gamma(1/3)/(pi*r^(1/3)),
1,
1/24*2^(2/3)*(sqrt(3) + 4/(sqrt(3) + I) + I)*gamma(1/3)/(pi*r^(1/3)))
sage: r = SR('r')
sage: tuple((a*r^(1/3)).full_simplify() / r^(1/3) for a in asy)  # make nicer coefficients
(1/12*sqrt(3)*2^(2/3)*gamma(1/3)/(pi*r^(1/3)),
1,
1/12*sqrt(3)*2^(2/3)*gamma(1/3)/(pi*r^(1/3)))
sage: F.relative_error(asy[0], alpha, [1, 2, 4, 8, 16], asy[1])
[((4, 1), 0.1875000000, [0.1953794675...], [-0.042023826...]),
((8, 2), 0.1523437500, [0.1550727862...], [-0.017913673...]),
((16, 4), 0.1221771240, [0.1230813519...], [-0.0074009592...]),
((32, 8), 0.09739671811, [0.09768973377...], [-0.0030084757...]),
((64, 16), 0.07744253816, [0.07753639308...], [-0.0012119297...])]


A multiple point example (Example 6.5 of [RW2012]):

sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: H = (1 - 2*x - y)**2 * (1 - x - 2*y)**2
sage: Hfac = H.factor()
sage: G = 1/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: F
(1, [(x + 2*y - 1, 2), (2*x + y - 1, 2)])
sage: I = F.singular_ideal()
sage: I
Ideal (x - 1/3, y - 1/3) of
Multivariate Polynomial Ring in x, y over Rational Field
sage: p = {x: 1/3, y: 1/3}
sage: F.is_convenient_multiple_point(p)
(True, 'convenient in variables [x, y]')
sage: alpha = (var('a'), var('b'))
sage: decomp =  F.asymptotic_decomposition(alpha); decomp
(0, []) +
(-1/9*r^2*(2*a^2/x^2 + 2*b^2/y^2 - 5*a*b/(x*y))
- 1/9*r*(6*a/x^2 + 6*b/y^2 - 5*a/(x*y) - 5*b/(x*y))
- 4/9/x^2 - 4/9/y^2 + 5/9/(x*y),
[(x + 2*y - 1, 1), (2*x + y - 1, 1)])
sage: F1 = decomp[1]
sage: F1.asymptotics(p, alpha, 2)
(-3*((2*a^2 - 5*a*b + 2*b^2)*r^2 + (a + b)*r + 3)*(1/((1/3)^a*(1/3)^b))^r,
1/((1/3)^a*(1/3)^b), -3*(2*a^2 - 5*a*b + 2*b^2)*r^2 - 3*(a + b)*r - 9)
sage: alpha = [4, 3]
sage: decomp =  F.asymptotic_decomposition(alpha)
sage: F1 = decomp[1]
sage: asy = F1.asymptotics(p, alpha, 2)
sage: asy
(3*(10*r^2 - 7*r - 3)*2187^r, 2187, 30*r^2 - 21*r - 9)
sage: F.relative_error(asy[0], alpha, [1, 2, 4, 8], asy[1])
[((4, 3), 30.72702332, [0.0000000000], [1.000000000]),
((8, 6), 111.9315678, [69.00000000], [0.3835519207]),
((16, 12), 442.7813138, [387.0000000], [0.1259793763]),
((32, 24), 1799.879232, [1743.000000], [0.03160169385])]


## Various¶

AUTHORS:

• Alexander Raichev (2008)

• Daniel Krenn (2014, 2016)

## Classes and Methods¶

class sage.rings.asymptotic.asymptotics_multivariate_generating_functions.FractionWithFactoredDenominator(parent, numerator, denominator_factored, reduce=True)

This element represents a fraction with a factored polynomial denominator. See also its parent FractionWithFactoredDenominatorRing for details.

Represents a fraction with factored polynomial denominator (FFPD) $$p/(q_1^{e_1} \cdots q_n^{e_n})$$ by storing the parts $$p$$ and $$[(q_1, e_1), \ldots, (q_n, e_n)]$$. Here $$q_1, \ldots, q_n$$ are elements of a 0- or multi-variate factorial polynomial ring $$R$$ , $$q_1, \ldots, q_n$$ are distinct irreducible elements of $$R$$ , $$e_1, \ldots, e_n$$ are positive integers, and $$p$$ is a function of the indeterminates of $$R$$ (e.g., a Sage symbolic expression). An element $$r$$ with no polynomial denominator is represented as (r, []).

INPUT:

• numerator – an element $$p$$; this can be of any ring from which parent’s base has coercion in

• denominator_factored – a list of the form $$[(q_1, e_1), \ldots, (q_n, e_n)]$$, where the $$q_1, \ldots, q_n$$ are distinct irreducible elements of $$R$$ and the $$e_i$$ are positive integers

• reduce – (optional) if True, then represent $$p/(q_1^{e_1} \cdots q_n^{e_n})$$ in lowest terms, otherwise this won’t attempt to divide $$p$$ by any of the $$q_i$$

OUTPUT:

An element representing the rational expression $$p/(q_1^{e_1} \cdots q_n^{e_n})$$.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: df = [x, 1], [y, 1], [x*y+1, 1]
sage: f = FFPD(x, df)
sage: f
(1, [(y, 1), (x*y + 1, 1)])
sage: ff = FFPD(x, df, reduce=False)
sage: ff
(x, [(y, 1), (x, 1), (x*y + 1, 1)])

sage: f = FFPD(x + y, [(x + y, 1)])
sage: f
(1, [])

sage: R.<x> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: f = 5*x^3 + 1/x + 1/(x-1) + 1/(3*x^2 + 1)
sage: FFPD(f)
(5*x^7 - 5*x^6 + 5/3*x^5 - 5/3*x^4 + 2*x^3 - 2/3*x^2 + 1/3*x - 1/3,
[(x - 1, 1), (x, 1), (x^2 + 1/3, 1)])

sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: f = 2*y/(5*(x^3 - 1)*(y + 1))
sage: FFPD(f)
(2/5*y, [(y + 1, 1), (x - 1, 1), (x^2 + x + 1, 1)])

sage: p = 1/x^2
sage: q = 3*x**2*y
sage: qs = q.factor()
sage: f = FFPD(p/qs.unit(), qs)
sage: f
(1/3/x^2, [(y, 1), (x, 2)])

sage: f = FFPD(cos(x)*x*y^2, [(x, 2), (y, 1)])
sage: f
(x*y^2*cos(x), [(y, 1), (x, 2)])

sage: G = exp(x + y)
sage: H = (1 - 2*x - y) * (1 - x - 2*y)
sage: a = FFPD(G/H)
sage: a
(e^(x + y), [(x + 2*y - 1, 1), (2*x + y - 1, 1)])
sage: a.denominator_ring
Multivariate Polynomial Ring in x, y over Rational Field
sage: b = FFPD(G, H.factor())
sage: b
(e^(x + y), [(x + 2*y - 1, 1), (2*x + y - 1, 1)])
sage: b.denominator_ring
Multivariate Polynomial Ring in x, y over Rational Field


Singular throws a ‘not implemented’ error when trying to factor in a multivariate polynomial ring over an inexact field:

sage: R.<x,y> = PolynomialRing(CC)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: f = (x + 1)/(x*y*(x*y + 1)^2)
sage: FFPD(f)
Traceback (most recent call last):
...
TypeError: Singular error:
? not implemented
? error occurred in or before STDIN line ...:
def sage...=factorize(sage...);


AUTHORS:

• Alexander Raichev (2012-07-26)

• Daniel Krenn (2014-12-01)

algebraic_dependence_certificate()

Return the algebraic dependence certificate of self.

The algebraic dependence certificate is the ideal $$J$$ of annihilating polynomials for the set of polynomials [q^e for (q, e) in self.denominator_factored()], which could be the zero ideal. The ideal $$J$$ lies in a polynomial ring over the field self.denominator_ring.base_ring() that has m = len(self.denominator_factored()) indeterminates.

OUTPUT:

An ideal.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: f = 1/(x^2 * (x*y + 1) * y^3)
sage: ff = FFPD(f)
sage: J = ff.algebraic_dependence_certificate(); J
Ideal (1 - 6*T2 + 15*T2^2 - 20*T2^3 + 15*T2^4 - T0^2*T1^3 -
6*T2^5  + T2^6) of Multivariate Polynomial Ring in
T0, T1, T2 over Rational Field
sage: g = J.gens()[0]
sage: df = ff.denominator_factored()
sage: g(*(q**e for q, e in df)) == 0
True

sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: G = exp(x + y)
sage: H = x^2 * (x*y + 1) * y^3
sage: ff = FFPD(G, H.factor())
sage: J = ff.algebraic_dependence_certificate(); J
Ideal (1 - 6*T2 + 15*T2^2 - 20*T2^3 + 15*T2^4 - T0^2*T1^3 -
6*T2^5 + T2^6) of Multivariate Polynomial Ring in
T0, T1, T2 over Rational Field
sage: g = J.gens()[0]
sage: df = ff.denominator_factored()
sage: g(*(q**e for q, e in df)) == 0
True

sage: f = 1/(x^3 * y^2)
sage: J = FFPD(f).algebraic_dependence_certificate()
sage: J
Ideal (0) of Multivariate Polynomial Ring in T0, T1 over Rational Field

sage: f = sin(1)/(x^3 * y^2)
sage: J = FFPD(f).algebraic_dependence_certificate()
sage: J
Ideal (0) of Multivariate Polynomial Ring in T0, T1 over Rational Field

algebraic_dependence_decomposition(whole_and_parts=True)

Return an algebraic dependence decomposition of self.

Let $$f = p/q$$ where $$q$$ lies in a $$d$$-variate polynomial ring $$K[X]$$ for some field $$K$$. Let $$q_1^{e_1} \cdots q_n^{e_n}$$ be the unique factorization of $$q$$ in $$K[X]$$ into irreducible factors and let $$V_i$$ be the algebraic variety $$\{x \in L^d \mid q_i(x) = 0\}$$ of $$q_i$$ over the algebraic closure $$L$$ of $$K$$. By [Rai2012], $$f$$ can be written as

$(*) \quad \sum_A \frac{p_A}{\prod_{i \in A} q_i^{b_i}},$

where the $$b_i$$ are positive integers, each $$p_A$$ is a products of $$p$$ and an element in $$K[X]$$, and the sum is taken over all subsets $$A \subseteq \{1, \ldots, m\}$$ such that $$|A| \leq d$$ and $$\{q_i \mid i \in A\}$$ is algebraically independent.

We call $$(*)$$ an algebraic dependence decomposition of $$f$$. Algebraic dependence decompositions are not unique.

The algorithm used comes from [Rai2012].

OUTPUT:

An instance of FractionWithFactoredDenominatorSum.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: f = 1/(x^2 * (x*y + 1) * y^3)
sage: ff = FFPD(f)
sage: decomp = ff.algebraic_dependence_decomposition()
sage: decomp
(0, []) + (-x, [(x*y + 1, 1)]) +
(x^2*y^2 - x*y + 1, [(y, 3), (x, 2)])
sage: decomp.sum().quotient() == f
True
sage: for r in decomp:
....:     J = r.algebraic_dependence_certificate()
....:     J is None or J == J.ring().ideal()  # The zero ideal
True
True
True

sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: G = sin(x)
sage: H = x^2 * (x*y + 1) * y^3
sage: f = FFPD(G, H.factor())
sage: decomp = f.algebraic_dependence_decomposition()
sage: decomp
(0, []) + (x^4*y^3*sin(x), [(x*y + 1, 1)]) +
(-(x^5*y^5 - x^4*y^4 + x^3*y^3 - x^2*y^2 + x*y - 1)*sin(x),
[(y, 3), (x, 2)])
sage: bool(decomp.sum().quotient() == G/H)
True
sage: for r in decomp:
....:     J = r.algebraic_dependence_certificate()
....:     J is None or J == J.ring().ideal()
True
True
True

asymptotic_decomposition(alpha, asy_var=None)

Return the asymptotic decomposition of self.

The asymptotic decomposition of $$F$$ is a sum that has the same asymptotic expansion as $$f$$ in the direction alpha but each summand has a denominator factorization of the form $$[(q_1, 1), \ldots, (q_n, 1)]$$, where $$n$$ is at most the dimension() of $$F$$.

INPUT:

• alpha – a $$d$$-tuple of positive integers or symbolic variables

• asy_var – (default: None) a symbolic variable with respect to which to compute asymptotics; if None is given, we set asy_var = var('r')

OUTPUT:

An instance of FractionWithFactoredDenominatorSum.

The output results from a Leinartas decomposition followed by a cohomology decomposition.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: f = (x^2 + 1)/((x - 1)^3*(x + 2))
sage: F = FFPD(f)
sage: alpha = [var('a')]
sage: F.asymptotic_decomposition(alpha)
(0, []) +
(1/54*(5*a^2 + 2*a^2/x + 11*a^2/x^2)*r^2
- 1/54*(5*a - 2*a/x - 33*a/x^2)*r + 11/27/x^2,
[(x - 1, 1)]) + (-5/27, [(x + 2, 1)])

sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: H = (1 - 2*x -y)*(1 - x -2*y)**2
sage: Hfac = H.factor()
sage: G = 1/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: alpha = var('a, b')
sage: F.asymptotic_decomposition(alpha)
(0, []) +
(-1/3*r*(a/x - 2*b/y) - 1/3/x + 2/3/y,
[(x + 2*y - 1, 1), (2*x + y - 1, 1)])

asymptotics(p, alpha, N, asy_var=None, numerical=0, verbose=False)

Return the asymptotics in the given direction.

This function returns the first $$N$$ terms (some of which could be zero) of the asymptotic expansion of the Maclaurin ray coefficients $$F_{r \alpha}$$ of the function $$F$$ represented by self as $$r \to \infty$$, where $$r$$ is asy_var and alpha is a tuple of positive integers of length $$d$$ which is self.dimension(). Assume that

• $$F$$ is holomorphic in a neighborhood of the origin;

• the unique factorization of the denominator $$H$$ of $$F$$ in the local algebraic ring at $$p$$ equals its unique factorization in the local analytic ring at $$p$$;

• the unique factorization of $$H$$ in the local algebraic ring at $$p$$ has at most d irreducible factors, none of which are repeated (one can reduce to this case via asymptotic_decomposition());

• $$p$$ is a convenient strictly minimal smooth or multiple point with all nonzero coordinates that is critical and nondegenerate for alpha.

The algorithms used here come from [RW2008] and [RW2012].

INPUT:

• p – a dictionary with keys that can be coerced to equal self.denominator_ring.gens()

• alpha – a tuple of length self.dimension() of positive integers or, if $$p$$ is a smooth point, possibly of symbolic variables

• N – a positive integer

• asy_var – (default: None) a symbolic variable for the asymptotic expansion; if none is given, then var('r') will be assigned

• numerical – (default: 0) a natural number; if numerical is greater than 0, then return a numerical approximation of $$F_{r \alpha}$$ with numerical digits of precision; otherwise return exact values

• verbose – (default: False) print the current state of the algorithm

OUTPUT:

The tuple (asy, exp_scale, subexp_part). Here asy is the sum of the first $$N$$ terms (some of which might be 0) of the asymptotic expansion of $$F_{r\alpha}$$ as $$r \to \infty$$; exp_scale**r is the exponential factor of asy; subexp_part is the subexponential factor of asy.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing


A smooth point example:

sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: H = (1 - x - y - x*y)**2
sage: Hfac = H.factor()
sage: G = 1/Hfac.unit()
sage: F = FFPD(G, Hfac); print(F)
(1, [(x*y + x + y - 1, 2)])
sage: alpha = [4, 3]
sage: decomp = F.asymptotic_decomposition(alpha); decomp
(0, []) + (-2*r*(1/x + 1) - 1/2/x - 1/2, [(x*y + x + y - 1, 1)])
sage: F1 = decomp[1]
sage: p = {y: 1/3, x: 1/2}
sage: asy = F1.asymptotics(p, alpha, 2, verbose=True)
Creating auxiliary functions...
Computing derivatives of auxiliary functions...
Computing derivatives of more auxiliary functions...
Computing second order differential operator actions...
sage: asy
(1/6000*(3600*sqrt(5)*sqrt(3)*sqrt(2)*sqrt(r)/sqrt(pi)
+ 463*sqrt(5)*sqrt(3)*sqrt(2)/(sqrt(pi)*sqrt(r)))*432^r,
432,
3/5*sqrt(5)*sqrt(3)*sqrt(2)*sqrt(r)/sqrt(pi)
+ 463/6000*sqrt(5)*sqrt(3)*sqrt(2)/(sqrt(pi)*sqrt(r)))
sage: F.relative_error(asy[0], alpha, [1, 2, 4, 8, 16], asy[1])  # abs tol 1e-10
[((4, 3), 2.083333333, [2.092576110], [-0.004436533009]),
((8, 6), 2.787374614, [2.790732875], [-0.001204811281]),
((16, 12), 3.826259447, [3.827462310], [-0.0003143703383]),
((32, 24), 5.328112821, [5.328540787], [-0.00008032230388]),
((64, 48), 7.475927885, [7.476079664], [-0.00002030232879])]


A multiple point example:

sage: R.<x,y,z>= PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: H = (4 - 2*x - y - z)**2*(4 - x - 2*y - z)
sage: Hfac = H.factor()
sage: G = 16/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: F
(-16, [(x + 2*y + z - 4, 1), (2*x + y + z - 4, 2)])
sage: alpha = [3, 3, 2]
sage: decomp = F.asymptotic_decomposition(alpha); decomp
(0, []) +
(16*r*(3/x - 2/z) + 16/x - 16/z,
[(x + 2*y + z - 4, 1), (2*x + y + z - 4, 1)])
sage: F1 = decomp[1]
sage: p = {x: 1, y: 1, z: 1}
sage: asy = F1.asymptotics(p, alpha, 2, verbose=True) # long time
Creating auxiliary functions...
Computing derivatives of auxiliary functions...
Computing derivatives of more auxiliary functions...
Computing second-order differential operator actions...
sage: asy # long time
(4/3*sqrt(3)*sqrt(r)/sqrt(pi) + 47/216*sqrt(3)/(sqrt(pi)*sqrt(r)),
1, 4/3*sqrt(3)*sqrt(r)/sqrt(pi) + 47/216*sqrt(3)/(sqrt(pi)*sqrt(r)))
sage: F.relative_error(asy[0], alpha, [1, 2, 4, 8], asy[1]) # long time
[((3, 3, 2), 0.9812164307, [1.515572606], [-0.54458543...]),
((6, 6, 4), 1.576181132, [1.992989399], [-0.26444185...]),
((12, 12, 8), 2.485286378, [2.712196351], [-0.091301338...]),
((24, 24, 16), 3.700576827, [3.760447895], [-0.016178847...])]

asymptotics_multiple(p, alpha, N, asy_var, coordinate=None, numerical=0, verbose=False)

Return the asymptotics in the given direction of a multiple point nondegenerate for alpha.

This is the same as asymptotics(), but only in the case of a convenient multiple point nondegenerate for alpha. Assume also that self.dimension >= 2 and that the p.values() are not symbolic variables.

The formulas used for computing the asymptotic expansion are Theorem 3.4 and Theorem 3.7 of [RW2012].

INPUT:

• p – a dictionary with keys that can be coerced to equal self.denominator_ring.gens()

• alpha – a tuple of length d = self.dimension() of positive integers or, if $$p$$ is a smooth point, possibly of symbolic variables

• N – a positive integer

• asy_var – (optional; default: None) a symbolic variable; the variable of the asymptotic expansion, if none is given, var('r') will be assigned

• coordinate – (optional; default: None) an integer in $$\{0, \ldots, d-1\}$$ indicating a convenient coordinate to base the asymptotic calculations on; if None is assigned, then choose coordinate=d-1

• numerical – (optional; default: 0) a natural number; if numerical is greater than 0, then return a numerical approximation of the Maclaurin ray coefficients of self with numerical digits of precision; otherwise return exact values

• verbose – (default: False) print the current state of the algorithm

OUTPUT:

The asymptotic expansion.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y,z>= PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: H = (4 - 2*x - y - z)*(4 - x -2*y - z)
sage: Hfac = H.factor()
sage: G = 16/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: F
(16, [(x + 2*y + z - 4, 1), (2*x + y + z - 4, 1)])
sage: p = {x: 1, y: 1, z: 1}
sage: alpha = [3, 3, 2]
sage: F.asymptotics_multiple(p, alpha, 2, var('r'), verbose=True) # long time
Creating auxiliary functions...
Computing derivatives of auxiliary functions...
Computing derivatives of more auxiliary functions...
Computing second-order differential operator actions...
(4/3*sqrt(3)/(sqrt(pi)*sqrt(r)) - 25/216*sqrt(3)/(sqrt(pi)*r^(3/2)),
1,
4/3*sqrt(3)/(sqrt(pi)*sqrt(r)) - 25/216*sqrt(3)/(sqrt(pi)*r^(3/2)))

sage: H = (1 - x*(1 + y))*(1 - z*x**2*(1 + 2*y))
sage: Hfac = H.factor()
sage: G = 1/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: F
(1, [(x*y + x - 1, 1), (2*x^2*y*z + x^2*z - 1, 1)])
sage: p = {x: 1/2, z: 4/3, y: 1}
sage: alpha = [8, 3, 3]
sage: F.asymptotics_multiple(p, alpha, 2, var('r'), coordinate=1, verbose=True) # long time
Creating auxiliary functions...
Computing derivatives of auxiliary functions...
Computing derivatives of more auxiliary functions...
Computing second-order differential operator actions...
(1/172872*108^r*(24696*sqrt(7)*sqrt(3)/(sqrt(pi)*sqrt(r))
- 1231*sqrt(7)*sqrt(3)/(sqrt(pi)*r^(3/2))),
108,
1/7*sqrt(7)*sqrt(3)/(sqrt(pi)*sqrt(r))
- 1231/172872*sqrt(7)*sqrt(3)/(sqrt(pi)*r^(3/2)))

sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: H = (1 - 2*x - y) * (1 - x - 2*y)
sage: Hfac = H.factor()
sage: G = exp(x + y)/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: F
(e^(x + y), [(x + 2*y - 1, 1), (2*x + y - 1, 1)])
sage: p = {x: 1/3, y: 1/3}
sage: alpha = (var('a'), var('b'))
sage: F.asymptotics_multiple(p, alpha, 2, var('r')) # long time
(3*(1/((1/3)^a*(1/3)^b))^r*e^(2/3), 1/((1/3)^a*(1/3)^b), 3*e^(2/3))

asymptotics_smooth(p, alpha, N, asy_var, coordinate=None, numerical=0, verbose=False)

Return the asymptotics in the given direction of a smooth point.

This is the same as asymptotics(), but only in the case of a convenient smooth point.

The formulas used for computing the asymptotic expansions are Theorems 3.2 and 3.3 [RW2008] with the exponent of $$H$$ equal to 1. Theorem 3.2 is a specialization of Theorem 3.4 of [RW2012] with $$n = 1$$.

INPUT:

• p – a dictionary with keys that can be coerced to equal self.denominator_ring.gens()

• alpha – a tuple of length d = self.dimension() of positive integers or, if $$p$$ is a smooth point, possibly of symbolic variables

• N – a positive integer

• asy_var – (optional; default: None) a symbolic variable; the variable of the asymptotic expansion, if none is given, var('r') will be assigned

• coordinate – (optional; default: None) an integer in $$\{0, \ldots, d-1\}$$ indicating a convenient coordinate to base the asymptotic calculations on; if None is assigned, then choose coordinate=d-1

• numerical – (optional; default: 0) a natural number; if numerical is greater than 0, then return a numerical approximation of the Maclaurin ray coefficients of self with numerical digits of precision; otherwise return exact values

• verbose – (default: False) print the current state of the algorithm

OUTPUT:

The asymptotic expansion.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: H = 2 - 3*x
sage: Hfac = H.factor()
sage: G = 1/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: F
(-1/3, [(x - 2/3, 1)])
sage: alpha = [2]
sage: p = {x: 2/3}
sage: asy = F.asymptotics_smooth(p, alpha, 3, asy_var=var('r'))
sage: asy
(1/2*(9/4)^r, 9/4, 1/2)

sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: H = 1-x-y-x*y
sage: Hfac = H.factor()
sage: G = 1/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: alpha = [3, 2]
sage: p = {y: 1/2*sqrt(13) - 3/2, x: 1/3*sqrt(13) - 2/3}
sage: F.asymptotics_smooth(p, alpha, 2, var('r'), numerical=3, verbose=True)
Creating auxiliary functions...
Computing derivatives of auxiliary functions...
Computing derivatives of more auxiliary functions...
Computing second order differential operator actions...
(71.2^r*(0.369/sqrt(r) - 0.018.../r^(3/2)), 71.2, 0.369/sqrt(r) - 0.018.../r^(3/2))

sage: q = 1/2
sage: qq = q.denominator()
sage: H = 1 - q*x + q*x*y - x^2*y
sage: Hfac = H.factor()
sage: G = (1 - q*x)/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: alpha = list(qq*vector([2, 1 - q]))
sage: alpha
[4, 1]
sage: p = {x: 1, y: 1}
sage: F.asymptotics_smooth(p, alpha, 5, var('r'), verbose=True) # not tested (140 seconds)
Creating auxiliary functions...
Computing derivatives of auxiliary functions...
Computing derivatives of more auxiliary functions...
Computing second order differential operator actions...
(1/12*sqrt(3)*2^(2/3)*gamma(1/3)/(pi*r^(1/3))
- 1/96*sqrt(3)*2^(1/3)*gamma(2/3)/(pi*r^(5/3)),
1,
1/12*sqrt(3)*2^(2/3)*gamma(1/3)/(pi*r^(1/3))
- 1/96*sqrt(3)*2^(1/3)*gamma(2/3)/(pi*r^(5/3)))

cohomology_decomposition()

Return the cohomology decomposition of self.

Let $$p / (q_1^{e_1} \cdots q_n^{e_n})$$ be the fraction represented by self and let $$K[x_1, \ldots, x_d]$$ be the polynomial ring in which the $$q_i$$ lie. Assume that $$n \leq d$$ and that the gradients of the $$q_i$$ are linearly independent at all points in the intersection $$V_1 \cap \ldots \cap V_n$$ of the algebraic varieties $$V_i = \{x \in L^d \mid q_i(x) = 0 \}$$, where $$L$$ is the algebraic closure of the field $$K$$. Return a FractionWithFactoredDenominatorSum $$f$$ such that the differential form $$f dx_1 \wedge \cdots \wedge dx_d$$ is de Rham cohomologous to the differential form $$p / (q_1^{e_1} \cdots q_n^{e_n}) dx_1 \wedge \cdots \wedge dx_d$$ and such that the denominator of each summand of $$f$$ contains no repeated irreducible factors.

The algorithm used here comes from the proof of Theorem 17.4 of [AY1983].

OUTPUT:

An instance of FractionWithFactoredDenominatorSum.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: f = 1/(x^2 + x + 1)^3
sage: decomp = FFPD(f).cohomology_decomposition()
sage: decomp
(0, []) + (2/3, [(x^2 + x + 1, 1)])

sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: FFPD(1, [(x, 1), (y, 2)]).cohomology_decomposition()
(0, [])


The following example was fixed in trac ticket #29465:

sage: p = 1
sage: qs = [(x*y - 1, 1), (x**2 + y**2 - 1, 2)]
sage: f = FFPD(p, qs)
sage: f.cohomology_decomposition()
(0, []) + (-4/3*x*y, [(x^2 + y^2 - 1, 1)]) +
(1/3, [(x*y - 1, 1), (x^2 + y^2 - 1, 1)])

critical_cone(p, coordinate=None)

Return the critical cone of the convenient multiple point p.

INPUT:

• p – a dictionary with keys that can be coerced to equal self.denominator_ring.gens() and values in a field

• coordinate – (optional; default: None) a natural number

OUTPUT:

A list of vectors.

This list of vectors generate the critical cone of p and the cone itself, which is None if the values of p don’t lie in $$\QQ$$. Divide logarithmic gradients by their component coordinate entries. If coordinate = None, then search from $$d-1$$ down to 0 for the first index j such that for all i we have self.log_grads()[i][j] != 0 and set coordinate = j.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y,z> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: G = 1
sage: H = (1 - x*(1 + y)) * (1 - z*x**2*(1 + 2*y))
sage: Hfac = H.factor()
sage: G = 1/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: p = {x: 1/2, y: 1, z: 4/3}
sage: F.critical_cone(p)
([(2, 1, 0), (3, 1, 3/2)], 2-d cone in 3-d lattice N)

denominator()

Return the denominator of self.

OUTPUT:

The denominator (i.e., the product of the factored denominator).

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: H = (1 - x - y - x*y)**2*(1-x)
sage: Hfac = H.factor()
sage: G = exp(y)/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: F.denominator()
x^3*y^2 + 2*x^3*y + x^2*y^2 + x^3 - 2*x^2*y - x*y^2 - 3*x^2 - 2*x*y
- y^2 + 3*x + 2*y - 1

denominator_factored()

Return the factorization in self.denominator_ring of the denominator of self but without the unit part.

OUTPUT:

The factored denominator as a list of tuple (f, m), where $$f$$ is a factor and $$m$$ its multiplicity.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: H = (1 - x - y - x*y)**2*(1-x)
sage: Hfac = H.factor()
sage: G = exp(y)/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: F.denominator_factored()
[(x - 1, 1), (x*y + x + y - 1, 2)]

denominator_ring

Return the ring of the denominator.

OUTPUT:

A ring.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: H = (1 - x - y - x*y)**2*(1-x)
sage: Hfac = H.factor()
sage: G = exp(y)/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: F.denominator_ring
Multivariate Polynomial Ring in x, y over Rational Field
sage: F = FFPD(G/H)
sage: F
(e^y, [(x - 1, 1), (x*y + x + y - 1, 2)])
sage: F.denominator_ring
Multivariate Polynomial Ring in x, y over Rational Field

dimension()

Return the number of indeterminates of self.denominator_ring.

OUTPUT:

An integer.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: H = (1 - x - y - x*y)**2*(1-x)
sage: Hfac = H.factor()
sage: G = exp(y)/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: F.dimension()
2


Return a list of the gradients of the polynomials [q for (q, e) in self.denominator_factored()] evaluated at p.

INPUT:

• p – (optional; default: None) a dictionary whose keys are the generators of self.denominator_ring

OUTPUT:

A list.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: p = exp(x)
sage: df = [(x^3 + 3*y^2, 5), (x*y, 2), (y, 1)]
sage: f = FFPD(p, df)
sage: f
(e^x, [(y, 1), (x*y, 2), (x^3 + 3*y^2, 5)])
sage: R.gens()
(x, y)
sage: p = None
[(0, 1), (y, x), (3*x^2, 6*y)]

sage: p = {x: sqrt(2), y: var('a')}
[(0, 1), (a, sqrt(2)), (6, 6*a)]

is_convenient_multiple_point(p)

Tests if p is a convenient multiple point of self.

In case p is a convenient multiple point, verdict = True and comment is a string stating which variables it’s convenient to use. In case p is not, verdict = False and comment is a string explaining why p fails to be a convenient multiple point.

See [RW2012] for more details.

INPUT:

• p – a dictionary with keys that can be coerced to equal self.denominator_ring.gens()

OUTPUT:

A pair (verdict, comment).

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y,z> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: H = (1 - x*(1 + y)) * (1 - z*x**2*(1 + 2*y))
sage: df = H.factor()
sage: G = 1 / df.unit()
sage: F = FFPD(G, df)
sage: p1 = {x: 1/2, y: 1, z: 4/3}
sage: p2 = {x: 1, y: 2, z: 1/2}
sage: F.is_convenient_multiple_point(p1)
(True, 'convenient in variables [x, y]')
sage: F.is_convenient_multiple_point(p2)
(False, 'not a singular point')

leinartas_decomposition()

Return a Leinartas decomposition of self.

Let $$f = p/q$$ where $$q$$ lies in a $$d$$ -variate polynomial ring $$K[X]$$ for some field $$K$$. Let $$q_1^{e_1} \cdots q_n^{e_n}$$ be the unique factorization of $$q$$ in $$K[X]$$ into irreducible factors and let $$V_i$$ be the algebraic variety $$\{x\in L^d \mid q_i(x) = 0\}$$ of $$q_i$$ over the algebraic closure $$L$$ of $$K$$. By [Rai2012], $$f$$ can be written as

$(*) \quad \sum_A \frac{p_A}{\prod_{i \in A} q_i^{b_i}},$

where the $$b_i$$ are positive integers, each $$p_A$$ is a product of $$p$$ and an element of $$K[X]$$, and the sum is taken over all subsets $$A \subseteq \{1, \ldots, m\}$$ such that

1. $$|A| \le d$$,

2. $$\bigcap_{i\in A} T_i \neq \emptyset$$, and

3. $$\{q_i \mid i\in A\}$$ is algebraically independent.

In particular, any rational expression in $$d$$ variables can be represented as a sum of rational expressions whose denominators each contain at most $$d$$ distinct irreducible factors.

We call $$(*)$$ a Leinartas decomposition of $$f$$. Leinartas decompositions are not unique.

The algorithm used comes from [Rai2012].

OUTPUT:

An instance of FractionWithFactoredDenominatorSum.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: f = (x^2 + 1)/((x + 2)*(x - 1)*(x^2 + x + 1))
sage: decomp = FFPD(f).leinartas_decomposition()
sage: decomp
(0, []) + (2/9, [(x - 1, 1)]) +
(-5/9, [(x + 2, 1)]) + (1/3*x, [(x^2 + x + 1, 1)])
sage: decomp.sum().quotient() == f
True

sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: f = 1/x + 1/y + 1/(x*y + 1)
sage: decomp = FFPD(f).leinartas_decomposition()
sage: decomp
(0, []) + (1, [(x*y + 1, 1)]) + (x + y, [(y, 1), (x, 1)])
sage: decomp.sum().quotient() == f
True
sage: def check_decomp(r):
....:     L = r.nullstellensatz_certificate()
....:     J = r.algebraic_dependence_certificate()
....:     return L is None and (J is None or J == J.ring().ideal())
sage: all(check_decomp(r) for r in decomp)
True

sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: f = sin(x)/x + 1/y + 1/(x*y + 1)
sage: G = f.numerator()
sage: H = R(f.denominator())
sage: ff = FFPD(G, H.factor())
sage: decomp = ff.leinartas_decomposition()
sage: decomp
(0, []) +
(-(x*y^2*sin(x) + x^2*y + x*y + y*sin(x) + x)*y, [(y, 1)]) +
((x*y^2*sin(x) + x^2*y + x*y + y*sin(x) + x)*x*y, [(x*y + 1, 1)]) +
(x*y^2*sin(x) + x^2*y + x*y + y*sin(x) + x, [(y, 1), (x, 1)])
sage: bool(decomp.sum().quotient() == f)
True
sage: all(check_decomp(r) for r in decomp)
True

sage: R.<x,y,z>= PolynomialRing(GF(2, 'a'))
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: f = 1/(x * y * z * (x*y + z))
sage: decomp = FFPD(f).leinartas_decomposition()
sage: decomp
(0, []) + (1, [(z, 2), (x*y + z, 1)]) +
(1, [(z, 2), (y, 1), (x, 1)])
sage: decomp.sum().quotient() == f
True


Return a list of the logarithmic gradients of the polynomials [q for (q, e) in self.denominator_factored()] evaluated at p.

The logarithmic gradient of a function $$f$$ at point $$p$$ is the vector $$(x_1 \partial_1 f(x), \ldots, x_d \partial_d f(x) )$$ evaluated at $$p$$.

INPUT:

• p – (optional; default: None) a dictionary whose keys are the generators of self.denominator_ring

OUTPUT:

A list.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: p = exp(x)
sage: df = [(x^3 + 3*y^2, 5), (x*y, 2), (y, 1)]
sage: f = FFPD(p, df)
sage: f
(e^x, [(y, 1), (x*y, 2), (x^3 + 3*y^2, 5)])
sage: R.gens()
(x, y)
sage: p = None
[(0, y), (x*y, x*y), (3*x^3, 6*y^2)]

sage: p = {x: sqrt(2), y: var('a')}
[(0, a), (sqrt(2)*a, sqrt(2)*a), (6*sqrt(2), 6*a^2)]

maclaurin_coefficients(multi_indices, numerical=0)

Return the Maclaurin coefficients of self with given multi_indices.

INPUT:

• multi_indices – a list of tuples of positive integers, where each tuple has length self.dimension()

• numerical – (optional; default: 0) a natural number; if positive, return numerical approximations of coefficients with numerical digits of accuracy

OUTPUT:

A dictionary whose value of the key nu are the Maclaurin coefficient of index nu of self.

Note

Uses iterated univariate Maclaurin expansions. Slow.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: H = 2 - 3*x
sage: Hfac = H.factor()
sage: G = 1 / Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: F
(-1/3, [(x - 2/3, 1)])
sage: F.maclaurin_coefficients([(2*k,) for k in range(6)])
{(0,): 1/2,
(2,): 9/8,
(4,): 81/32,
(6,): 729/128,
(8,): 6561/512,
(10,): 59049/2048}

sage: R.<x,y,z> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: H = (4 - 2*x - y - z) * (4 - x - 2*y - z)
sage: Hfac = H.factor()
sage: G = 16 / Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: alpha = vector([3, 3, 2])
sage: interval = [1, 2, 4]
sage: S = [r*alpha for r in interval]
sage: F.maclaurin_coefficients(S, numerical=10)
{(3, 3, 2): 0.7849731445,
(6, 6, 4): 0.7005249476,
(12, 12, 8): 0.5847732654}

nullstellensatz_certificate()

Return a Nullstellensatz certificate of self if it exists.

Let $$[(q_1, e_1), \ldots, (q_n, e_n)]$$ be the denominator factorization of self. The Nullstellensatz certificate is a list of polynomials $$h_1, \ldots, h_m$$ in self.denominator_ring that satisfies $$h_1 q_1 + \cdots + h_m q_n = 1$$ if it exists.

Note

Only works for multivariate base rings.

OUTPUT:

A list of polynomials or None if no Nullstellensatz certificate exists.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: G = sin(x)
sage: H = x^2 * (x*y + 1)
sage: f = FFPD(G, H.factor())
sage: L = f.nullstellensatz_certificate()
sage: L
[y^2, -x*y + 1]
sage: df = f.denominator_factored()
sage: sum(L[i]*df[i][0]**df[i][1] for i in range(len(df))) == 1
True

sage: f = 1/(x*y)
sage: L = FFPD(f).nullstellensatz_certificate()
sage: L is None
True

nullstellensatz_decomposition()

Return a Nullstellensatz decomposition of self.

Let $$f = p/q$$ where $$q$$ lies in a $$d$$ -variate polynomial ring $$K[X]$$ for some field $$K$$ and $$d \geq 1$$. Let $$q_1^{e_1} \cdots q_n^{e_n}$$ be the unique factorization of $$q$$ in $$K[X]$$ into irreducible factors and let $$V_i$$ be the algebraic variety $$\{x \in L^d \mid q_i(x) = 0\}$$ of $$q_i$$ over the algebraic closure $$L$$ of $$K$$. By [Rai2012], $$f$$ can be written as

$(*) \quad \sum_A \frac{p_A}{\prod_{i \in A} q_i^{e_i}},$

where the $$p_A$$ are products of $$p$$ and elements in $$K[X]$$ and the sum is taken over all subsets $$A \subseteq \{1, \ldots, m\}$$ such that $$\bigcap_{i\in A} T_i \neq \emptyset$$.

We call $$(*)$$ a Nullstellensatz decomposition of $$f$$. Nullstellensatz decompositions are not unique.

The algorithm used comes from [Rai2012].

Note

Recursive. Only works for multivariate self.

OUTPUT:

An instance of FractionWithFactoredDenominatorSum.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import *
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: f = 1/(x*(x*y + 1))
sage: decomp = FFPD(f).nullstellensatz_decomposition()
sage: decomp
(0, []) + (1, [(x, 1)]) + (-y, [(x*y + 1, 1)])
sage: decomp.sum().quotient() == f
True
sage: [r.nullstellensatz_certificate() is None for r in decomp]
[True, True, True]

sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: G = sin(y)
sage: H = x*(x*y + 1)
sage: f = FFPD(G, H.factor())
sage: decomp = f.nullstellensatz_decomposition()
sage: decomp
(0, []) + (sin(y), [(x, 1)]) + (-y*sin(y), [(x*y + 1, 1)])
sage: bool(decomp.sum().quotient() == G/H)
True
sage: [r.nullstellensatz_certificate() is None for r in decomp]
[True, True, True]

numerator()

Return the numerator of self.

OUTPUT:

The numerator.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: H = (1 - x - y - x*y)**2*(1-x)
sage: Hfac = H.factor()
sage: G = exp(y)/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: F.numerator()
-e^y

numerator_ring

Return the ring of the numerator.

OUTPUT:

A ring.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: H = (1 - x - y - x*y)**2*(1-x)
sage: Hfac = H.factor()
sage: G = exp(y)/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: F.numerator_ring
Symbolic Ring
sage: F = FFPD(G/H)
sage: F
(e^y, [(x - 1, 1), (x*y + x + y - 1, 2)])
sage: F.numerator_ring
Symbolic Ring

quotient()

Convert self into a quotient.

OUTPUT:

An element.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: H = (1 - x - y - x*y)**2*(1-x)
sage: Hfac = H.factor()
sage: G = exp(y)/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: F
(-e^y, [(x - 1, 1), (x*y + x + y - 1, 2)])
sage: F.quotient()
-e^y/(x^3*y^2 + 2*x^3*y + x^2*y^2 + x^3 - 2*x^2*y - x*y^2 - 3*x^2 -
2*x*y - y^2 + 3*x + 2*y - 1)

relative_error(approx, alpha, interval, exp_scale=1, digits=10)

Return the relative error between the values of the Maclaurin coefficients of self with multi-indices r alpha for r in interval and the values of the functions (of the variable r) in approx.

INPUT:

• approx – an individual or list of symbolic expressions in one variable

• alpha - a list of positive integers of length self.denominator_ring.ngens()

• interval – a list of positive integers

• exp_scale – (optional; default: 1) a number

OUTPUT:

A list of tuples with properties described below.

This outputs a list whose entries are a tuple (r*alpha, a_r, b_r, err_r) for r in interval. Here r*alpha is a tuple; a_r is the r*alpha (multi-index) coefficient of the Maclaurin series for self divided by exp_scale**r; b_r is a list of the values of the functions in approx evaluated at r and divided by exp_scale**m; err_r is the list of relative errors (a_r - f)/a_r for f in b_r. All outputs are decimal approximations.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: H = 1 - x - y - x*y
sage: Hfac = H.factor()
sage: G = 1 / Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: alpha = [1, 1]
sage: r = var('r')
sage: a1 = (0.573/sqrt(r))*5.83^r
sage: a2 = (0.573/sqrt(r) - 0.0674/r^(3/2))*5.83^r
sage: es = 5.83
sage: F.relative_error([a1, a2], alpha, [1, 2, 4, 8], es) # long time
[((1, 1), 0.5145797599,
[0.5730000000, 0.5056000000], [-0.1135300000, 0.01745066667]),
((2, 2), 0.3824778089,
[0.4051721856, 0.3813426871], [-0.05933514614, 0.002967810973]),
((4, 4), 0.2778630595,
[0.2865000000, 0.2780750000], [-0.03108344267, -0.0007627515584]),
((8, 8), 0.1991088276,
[0.2025860928, 0.1996074055], [-0.01746414394, -0.002504047242])]

singular_ideal()

Return the singular ideal of self.

Let $$R$$ be the ring of self and $$H$$ its denominator. Let $$H_{red}$$ be the reduction (square-free part) of $$H$$. Return the ideal in $$R$$ generated by $$H_{red}$$ and its partial derivatives. If the coefficient field of $$R$$ is algebraically closed, then the output is the ideal of the singular locus (which is a variety) of the variety of $$H$$.

OUTPUT:

An ideal.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y,z> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: H = (1 - x*(1 + y))^3 * (1 - z*x**2*(1 + 2*y))
sage: df = H.factor()
sage: G = 1 / df.unit()
sage: F = FFPD(G, df)
sage: F.singular_ideal()
Ideal (x*y + x - 1, y^2 - 2*y*z + 2*y - z + 1, x*z + y - 2*z + 1) of
Multivariate Polynomial Ring in x, y, z over Rational Field

smooth_critical_ideal(alpha)

Return the smooth critical ideal of self.

Let $$R$$ be the ring of self and $$H$$ its denominator. Return the ideal in $$R$$ of smooth critical points of the variety of $$H$$ for the direction alpha. If the variety $$V$$ of $$H$$ has no smooth points, then return the ideal in $$R$$ of $$V$$.

See [RW2012] for more details.

INPUT:

• alpha – a tuple of positive integers and/or symbolic entries of length self.denominator_ring.ngens()

OUTPUT:

An ideal.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: H = (1 - x - y - x*y)^2
sage: Hfac = H.factor()
sage: G = 1/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: alpha = var('a1, a2')
sage: F.smooth_critical_ideal(alpha)
Ideal (y^2 + 2*a1/a2*y - 1, x + ((-a2)/a1)*y + (-a1 + a2)/a1) of
Multivariate Polynomial Ring in x, y over Fraction Field of
Multivariate Polynomial Ring in a1, a2 over Rational Field

sage: H = (1-x-y-x*y)^2
sage: Hfac = H.factor()
sage: G = 1/Hfac.unit()
sage: F = FFPD(G, Hfac)
sage: alpha = [7/3, var('a')]
sage: F.smooth_critical_ideal(alpha)
Ideal (y^2 + 14/3/a*y - 1, x + (-3/7*a)*y + 3/7*a - 1) of Multivariate Polynomial Ring in x, y over Fraction Field of Univariate Polynomial Ring in a over Rational Field

univariate_decomposition()

Return the usual univariate partial fraction decomposition of self.

Assume that the numerator of self lies in the same univariate factorial polynomial ring as the factors of the denominator.

Let $$f = p/q$$ be a rational expression where $$p$$ and $$q$$ lie in a univariate factorial polynomial ring $$R$$. Let $$q_1^{e_1} \cdots q_n^{e_n}$$ be the unique factorization of $$q$$ in $$R$$ into irreducible factors. Then $$f$$ can be written uniquely as:

$(*) \quad p_0 + \sum_{i=1}^{m} \frac{p_i}{q_i^{e_i}},$

for some $$p_j \in R$$. We call $$(*)$$ the usual partial fraction decomposition of $$f$$.

Note

This partial fraction decomposition can be computed using partial_fraction() or partial_fraction_decomposition() as well. However, here we use the already obtained/cached factorization of the denominator. This gives a speed up for non-small instances.

OUTPUT:

An instance of FractionWithFactoredDenominatorSum.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing


One variable:

sage: R.<x> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: f = 5*x^3 + 1/x + 1/(x-1) + 1/(3*x^2 + 1)
sage: f
(5*x^7 - 5*x^6 + 5/3*x^5 - 5/3*x^4 + 2*x^3 - 2/3*x^2 + 1/3*x - 1/3)/(x^4 - x^3 + 1/3*x^2 - 1/3*x)
sage: decomp = FFPD(f).univariate_decomposition()
sage: decomp
(5*x^3, []) +
(1, [(x - 1, 1)]) +
(1, [(x, 1)]) +
(1/3, [(x^2 + 1/3, 1)])
sage: decomp.sum().quotient() == f
True


One variable with numerator in symbolic ring:

sage: R.<x> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: f = 5*x^3 + 1/x + 1/(x-1) + exp(x)/(3*x^2 + 1)
sage: f
(5*x^5 - 5*x^4 + 2*x - 1)/(x^2 - x) + e^x/(3*x^2 + 1)
sage: decomp = FFPD(f).univariate_decomposition()
sage: decomp
(0, []) +
(15/4*x^7 - 15/4*x^6 + 5/4*x^5 - 5/4*x^4 + 3/2*x^3 + 1/4*x^2*e^x -
3/4*x^2 - 1/4*x*e^x + 1/2*x - 1/4, [(x - 1, 1)]) +
(-15*x^7 + 15*x^6 - 5*x^5 + 5*x^4 - 6*x^3 -
x^2*e^x + 3*x^2 + x*e^x - 2*x + 1, [(x, 1)]) +
(1/4*(15*x^7 - 15*x^6 + 5*x^5 - 5*x^4 + 6*x^3 + x^2*e^x -
3*x^2 - x*e^x + 2*x - 1)*(3*x - 1), [(x^2 + 1/3, 1)])


One variable over a finite field:

sage: R.<x> = PolynomialRing(GF(2))
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: f = 5*x^3 + 1/x + 1/(x-1) + 1/(3*x^2 + 1)
sage: f
(x^6 + x^4 + 1)/(x^3 + x)
sage: decomp = FFPD(f).univariate_decomposition()
sage: decomp
(x^3, []) + (1, [(x, 1)]) + (x, [(x + 1, 2)])
sage: decomp.sum().quotient() == f
True


One variable over an inexact field:

sage: R.<x> = PolynomialRing(CC)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: f = 5*x^3 + 1/x + 1/(x-1) + 1/(3*x^2 + 1)
sage: f
(5.00000000000000*x^7 - 5.00000000000000*x^6 + 1.66666666666667*x^5 - 1.66666666666667*x^4 + 2.00000000000000*x^3 - 0.666666666666667*x^2 + 0.333333333333333*x - 0.333333333333333)/(x^4 - x^3 + 0.333333333333333*x^2 - 0.333333333333333*x)
sage: decomp = FFPD(f).univariate_decomposition()
sage: decomp
(5.00000000000000*x^3, []) +
(1.00000000000000, [(x - 1.00000000000000, 1)]) +
(-0.288675134594813*I, [(x - 0.577350269189626*I, 1)]) +
(1.00000000000000, [(x, 1)]) +
(0.288675134594813*I, [(x + 0.577350269189626*I, 1)])
sage: decomp.sum().quotient() == f # Rounding error coming
False


AUTHORS:

• Robert Bradshaw (2007-05-31)

• Alexander Raichev (2012-06-25)

• Daniel Krenn (2014-12-01)

class sage.rings.asymptotic.asymptotics_multivariate_generating_functions.FractionWithFactoredDenominatorRing(denominator_ring, numerator_ring=None, category=None)

This is the ring of fractions with factored denominator.

INPUT:

• denominator_ring – the base ring (a polynomial ring)

• numerator_ring – (optional) the numerator ring; the default is the denominator_ring

• category – (default: Rings) the category

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: df = [x, 1], [y, 1], [x*y+1, 1]
sage: f = FFPD(x, df)  # indirect doctest
sage: f
(1, [(y, 1), (x*y + 1, 1)])


AUTHORS:

• Daniel Krenn (2014-12-01)

Element
base_ring()

Returns the base ring.

OUTPUT:

A ring.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing
sage: P.<X, Y> = ZZ[]
sage: F = FractionWithFactoredDenominatorRing(P); F
Ring of fractions with factored denominator
over Multivariate Polynomial Ring in X, Y over Integer Ring
sage: F.base_ring()
Integer Ring
sage: F.base()
Multivariate Polynomial Ring in X, Y over Integer Ring

class sage.rings.asymptotic.asymptotics_multivariate_generating_functions.FractionWithFactoredDenominatorSum

Bases: list

A list representing the sum of FractionWithFactoredDenominator objects with distinct denominator factorizations.

AUTHORS:

• Alexander Raichev (2012-06-25)

• Daniel Krenn (2014-12-01)

denominator_ring

Return the polynomial ring of the denominators of self.

OUTPUT:

A ring or None if the list is empty.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing, FractionWithFactoredDenominatorSum
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: f = FFPD(x + y, [(y, 1), (x, 1)])
sage: s = FractionWithFactoredDenominatorSum([f])
sage: s.denominator_ring
Multivariate Polynomial Ring in x, y over Rational Field
sage: g = FFPD(x + y, [])
sage: t = FractionWithFactoredDenominatorSum([g])
sage: t.denominator_ring
Multivariate Polynomial Ring in x, y over Rational Field

sum()

Return the sum of the elements in self.

OUTPUT:

An instance of FractionWithFactoredDenominator.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing, FractionWithFactoredDenominatorSum
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: df = (x, 1), (y, 1), (x*y + 1, 1)
sage: f = FFPD(2, df)
sage: g = FFPD(2*x*y, df)
sage: FractionWithFactoredDenominatorSum([f, g])
(2, [(y, 1), (x, 1), (x*y + 1, 1)]) + (2, [(x*y + 1, 1)])
sage: FractionWithFactoredDenominatorSum([f, g]).sum()
(2, [(y, 1), (x, 1)])

sage: f = FFPD(cos(x), [(x, 2)])
sage: g = FFPD(cos(y), [(x, 1), (y, 2)])
sage: FractionWithFactoredDenominatorSum([f, g])
(cos(x), [(x, 2)]) + (cos(y), [(y, 2), (x, 1)])
sage: FractionWithFactoredDenominatorSum([f, g]).sum()
(y^2*cos(x) + x*cos(y), [(y, 2), (x, 2)])

whole_and_parts()

Rewrite self as a sum of a (possibly zero) polynomial followed by reduced rational expressions.

OUTPUT:

An instance of FractionWithFactoredDenominatorSum.

Only useful for multivariate decompositions.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing, FractionWithFactoredDenominatorSum
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R, SR)
sage: f = x**2 + 3*y + 1/x + 1/y
sage: f = FFPD(f); f
(x^3*y + 3*x*y^2 + x + y, [(y, 1), (x, 1)])
sage: FractionWithFactoredDenominatorSum([f]).whole_and_parts()
(x^2 + 3*y, []) + (x + y, [(y, 1), (x, 1)])

sage: f = cos(x)**2 + 3*y + 1/x + 1/y; f
cos(x)^2 + 3*y + 1/x + 1/y
sage: G = f.numerator()
sage: H = R(f.denominator())
sage: f = FFPD(G, H.factor()); f
(x*y*cos(x)^2 + 3*x*y^2 + x + y, [(y, 1), (x, 1)])
sage: FractionWithFactoredDenominatorSum([f]).whole_and_parts()
(0, []) + (x*y*cos(x)^2 + 3*x*y^2 + x + y, [(y, 1), (x, 1)])

sage.rings.asymptotic.asymptotics_multivariate_generating_functions.coerce_point(R, p)

Coerce the keys of the dictionary p into the ring R.

Warning

This method assumes that it is possible.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import FractionWithFactoredDenominatorRing, coerce_point
sage: R.<x,y> = PolynomialRing(QQ)
sage: FFPD = FractionWithFactoredDenominatorRing(R)
sage: f = FFPD()
sage: p = {SR(x): 1, SR(y): 7/8}
sage: for k in sorted(p, key=str):
....:     print("{} {} {}".format(k, k.parent(), p[k]))
x Symbolic Ring 1
y Symbolic Ring 7/8
sage: q = coerce_point(R, p)
sage: for k in sorted(q, key=str):
....:     print("{} {} {}".format(k, k.parent(), q[k]))
x Multivariate Polynomial Ring in x, y over Rational Field 1
y Multivariate Polynomial Ring in x, y over Rational Field 7/8

sage.rings.asymptotic.asymptotics_multivariate_generating_functions.diff_all(f, V, n, ending=[], sub=None, sub_final=None, zero_order=0, rekey=None)

Return a dictionary of representative mixed partial derivatives of $$f$$ from order 1 up to order $$n$$ with respect to the variables in $$V$$.

The default is to key the dictionary by all nondecreasing sequences in $$V$$ of length 1 up to length $$n$$.

INPUT:

• f – an individual or list of $$\mathcal{C}^{n+1}$$ functions

• V – a list of variables occurring in $$f$$

• n – a natural number

• ending – a list of variables in $$V$$

• sub – an individual or list of dictionaries

• sub_final – an individual or list of dictionaries

• rekey – a callable symbolic function in $$V$$ or list thereof

• zero_order – a natural number

OUTPUT:

The dictionary {s_1:deriv_1, ..., sr:deriv_r}.

Here s_1, ..., s_r is a listing of all nondecreasing sequences of length 1 up to length $$n$$ over the alphabet $$V$$, where $$w > v$$ in $$X$$ if and only if str(w) > str(v), and deriv_j is the derivative of $$f$$ with respect to the derivative sequence s_j and simplified with respect to the substitutions in sub and evaluated at sub_final. Moreover, all derivatives with respect to sequences of length less than zero_order (derivatives of order less than zero_order ) will be made zero.

If rekey is nonempty, then s_1, ..., s_r will be replaced by the symbolic derivatives of the functions in rekey.

If ending is nonempty, then every derivative sequence s_j will be suffixed by ending.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import diff_all
sage: f = function('f')(x)
sage: dd = diff_all(f, [x], 3)
sage: dd[(x, x, x)]
diff(f(x), x, x, x)

sage: d1 = {diff(f, x): 4*x^3}
sage: dd = diff_all(f, [x], 3, sub=d1)
sage: dd[(x, x, x)]
24*x

sage: dd = diff_all(f, [x], 3, sub=d1, rekey=f)
sage: dd[diff(f, x, 3)]
24*x

sage: a = {x:1}
sage: dd = diff_all(f, [x], 3, sub=d1, rekey=f, sub_final=a)
sage: dd[diff(f, x, 3)]
24

sage: X = var('x, y, z')
sage: f = function('f')(*X)
sage: dd = diff_all(f, X, 2, ending=[y, y, y])
sage: dd[(z, y, y, y)]
diff(f(x, y, z), y, y, y, z)

sage: g = function('g')(*X)
sage: dd = diff_all([f, g], X, 2)
sage: dd[(0, y, z)]
diff(f(x, y, z), y, z)

sage: dd[(1, z, z)]
diff(g(x, y, z), z, z)

sage: f = exp(x*y*z)
sage: ff = function('ff')(*X)
sage: dd = diff_all(f, X, 2, rekey=ff)
sage: dd[diff(ff, x, z)]
x*y^2*z*e^(x*y*z) + y*e^(x*y*z)

sage.rings.asymptotic.asymptotics_multivariate_generating_functions.diff_op(A, B, AB_derivs, V, M, r, N)

Return the derivatives $$DD^{(l+k)}(A[j] B^l)$$ evaluated at a point $$p$$ for various natural numbers $$j, k, l$$ which depend on $$r$$ and $$N$$.

Here $$DD$$ is a specific second-order linear differential operator that depends on $$M$$ , $$A$$ is a list of symbolic functions, $$B$$ is symbolic function, and AB_derivs contains all the derivatives of $$A$$ and $$B$$ evaluated at $$p$$ that are necessary for the computation.

INPUT:

• A – a single or length r list of symbolic functions in the variables V

• B – a symbolic function in the variables V.

• AB_derivs – a dictionary whose keys are the (symbolic) derivatives of A[0], ..., A[r-1] up to order 2 * N-2 and the (symbolic) derivatives of B up to order 2 * N; the values of the dictionary are complex numbers that are the keys evaluated at a common point $$p$$

• V – the variables of the A[j] and B

• M – a symmetric $$l \times l$$ matrix, where $$l$$ is the length of V

• r, N – natural numbers

OUTPUT:

A dictionary.

The output is a dictionary whose keys are natural number tuples of the form $$(j, k, l)$$, where $$l \leq 2k$$, $$j \leq r-1$$, and $$j+k \leq N-1$$, and whose values are $$DD^(l+k)(A[j] B^l)$$ evaluated at a point $$p$$, where $$DD$$ is the linear second-order differential operator $$-\sum_{i=0}^{l-1} \sum_{j=0}^{l-1} M[i][j] \partial^2 /(\partial V[j] \partial V[i])$$.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import diff_op
sage: T = var('x, y')
sage: A = function('A')(*tuple(T))
sage: B = function('B')(*tuple(T))
sage: AB_derivs = {}
sage: M = matrix([[1, 2],[2, 1]])
sage: DD = diff_op(A, B, AB_derivs, T, M, 1, 2)
sage: sorted(DD)
[(0, 0, 0), (0, 1, 0), (0, 1, 1), (0, 1, 2)]
sage: DD[(0, 1, 2)].number_of_operands()
246

sage.rings.asymptotic.asymptotics_multivariate_generating_functions.diff_op_simple(A, B, AB_derivs, x, v, a, N)

Return $$DD^(e k + v l)(A B^l)$$ evaluated at a point $$p$$ for various natural numbers $$e, k, l$$ that depend on $$v$$ and $$N$$.

Here $$DD$$ is a specific linear differential operator that depends on $$a$$ and $$v$$ , $$A$$ and $$B$$ are symbolic functions, and $$AB_derivs$$ contains all the derivatives of $$A$$ and $$B$$ evaluated at $$p$$ that are necessary for the computation.

INPUT:

• A, B – Symbolic functions in the variable x

• AB_derivs - a dictionary whose keys are the (symbolic) derivatives of A up to order 2 * N if v is even or N if v is odd and the (symbolic) derivatives of B up to order 2 * N + v if v is even or N + v if v is odd; the values of the dictionary are complex numbers that are the keys evaluated at a common point $$p$$

• x – a symbolic variable

• a – a complex number

• v, N – natural numbers

OUTPUT:

A dictionary.

The output is a dictionary whose keys are natural number pairs of the form $$(k, l)$$, where $$k < N$$ and $$l \leq 2k$$ and whose values are $$DD^(e k + v l)(A B^l)$$ evaluated at a point $$p$$. Here $$e=2$$ if $$v$$ is even, $$e=1$$ if $$v$$ is odd, and $$DD$$ is the linear differential operator $$(a^{-1/v} d/dt)$$ if $$v$$ is even and $$(|a|^{-1/v} i \text{sgn}(a) d/dt)$$ if $$v$$ is odd.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import diff_op_simple
sage: A = function('A')(x)
sage: B = function('B')(x)
sage: AB_derivs = {}
sage: sorted(diff_op_simple(A, B, AB_derivs, x, 3, 2, 2).items())
[((0, 0), A(x)),
((1, 0), 1/2*I*2^(2/3)*diff(A(x), x)),
((1, 1),
1/4*2^(2/3)*(B(x)*diff(A(x), x, x, x, x) + 4*diff(A(x), x, x, x)*diff(B(x), x) + 6*diff(A(x), x, x)*diff(B(x), x, x) + 4*diff(A(x), x)*diff(B(x), x, x, x) + A(x)*diff(B(x), x, x, x, x)))]

sage.rings.asymptotic.asymptotics_multivariate_generating_functions.diff_prod(f_derivs, u, g, X, interval, end, uderivs, atc)

Take various derivatives of the equation $$f = ug$$, evaluate them at a point $$c$$, and solve for the derivatives of $$u$$.

INPUT:

• f_derivs – a dictionary whose keys are all tuples of the form s + end, where s is a sequence of variables from X whose length lies in interval, and whose values are the derivatives of a function $$f$$ evaluated at $$c$$

• u – a callable symbolic function

• g – an expression or callable symbolic function

• X – a list of symbolic variables

• interval – a list of positive integers Call the first and last values $$n$$ and $$nn$$, respectively

• end – a possibly empty list of repetitions of the variable z, where z is the last element of X

• uderivs – a dictionary whose keys are the symbolic derivatives of order 0 to order $$n-1$$ of u evaluated at $$c$$ and whose values are the corresponding derivatives evaluated at $$c$$

• atc – a dictionary whose keys are the keys of $$c$$ and all the symbolic derivatives of order 0 to order $$nn$$ of g evaluated $$c$$ and whose values are the corresponding derivatives evaluated at $$c$$

OUTPUT:

A dictionary whose keys are the derivatives of u up to order $$nn$$ and whose values are those derivatives evaluated at $$c$$.

This function works by differentiating the equation $$f = ug$$ with respect to the variable sequence s + end, for all tuples s of X of lengths in interval, evaluating at the point $$c$$ , and solving for the remaining derivatives of u. This function assumes that u never appears in the differentiations of $$f = ug$$ after evaluating at $$c$$.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import diff_prod
sage: u = function('u')(x)
sage: g = function('g')(x)
sage: fd = {(x,):1,(x, x):1}
sage: ud = {u(x=2): 1}
sage: atc = {x: 2, g(x=2): 3, diff(g, x)(x=2): 5}
sage: atc[diff(g, x, x)(x=2)] = 7
sage: dd = diff_prod(fd, u, g, [x], [1, 2], [], ud, atc)
sage: dd[diff(u, x, 2)(x=2)]
22/9

sage.rings.asymptotic.asymptotics_multivariate_generating_functions.diff_seq(V, s)

Given a list s of tuples of natural numbers, return the list of elements of V with indices the elements of the elements of s.

INPUT:

• V – a list

• s – a list of tuples of natural numbers in the interval range(len(V))

OUTPUT:

The tuple tuple([V[tt] for tt in sorted(t)]), where t is the list of elements of the elements of s.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import diff_seq
sage: V = list(var('x, t, z'))
sage: diff_seq(V,([0, 1],[0, 2, 1],[0, 0]))
(x, x, x, x, t, t, z)


Note

This function is for internal use by diff_op().

sage.rings.asymptotic.asymptotics_multivariate_generating_functions.direction(v, coordinate=None)

Return [vv/v[coordinate] for vv in v] where coordinate is the last index of v if not specified otherwise.

INPUT:

• v – a vector

• coordinate – (optional; default: None) an index for v

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import direction
sage: direction([2, 3, 5])
(2/5, 3/5, 1)
sage: direction([2, 3, 5], 0)
(1, 3/2, 5/2)

sage.rings.asymptotic.asymptotics_multivariate_generating_functions.permutation_sign(s, u)

This function returns the sign of the permutation on 1, ..., len(u) that is induced by the sublist s of u.

Note

This function was intended for internal use and is deprecated now (trac ticket #29465).

INPUT:

• s – a sublist of u

• u – a list

OUTPUT:

The sign of the permutation obtained by taking indices within u of the list s + sc, where sc is u with the elements of s removed.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import permutation_sign
sage: u = ['a', 'b', 'c', 'd', 'e']
sage: s = ['b', 'd']
sage: permutation_sign(s, u)
doctest:...: DeprecationWarning: the function permutation_sign is deprecated
See https://trac.sagemath.org/29465 for details.
-1
sage: s = ['d', 'b']
sage: permutation_sign(s, u)
1

sage.rings.asymptotic.asymptotics_multivariate_generating_functions.subs_all(f, sub, simplify=False)

Return the items of $$f$$ substituted by the dictionaries of sub in order of their appearance in sub.

INPUT:

• f – an individual or list of symbolic expressions or dictionaries

• sub – an individual or list of dictionaries

• simplify – (default: False) boolean; set to True to simplify the result

OUTPUT:

The items of f substituted by the dictionaries of sub in order of their appearance in sub. The subs() command is used. If simplify is True, then simplify() is used after substitution.

EXAMPLES:

sage: from sage.rings.asymptotic.asymptotics_multivariate_generating_functions import subs_all
sage: var('x, y, z')
(x, y, z)
sage: a = {x:1}
sage: b = {y:2}
sage: c = {z:3}
sage: subs_all(x + y + z, a)
y + z + 1
sage: subs_all(x + y + z, [c, a])
y + 4
sage: subs_all([x + y + z, y^2], b)
[x + z + 2, 4]
sage: subs_all([x + y + z, y^2], [b, c])
[x + 5, 4]

sage: var('x, y')
(x, y)
sage: a = {'foo': x**2 + y**2, 'bar': x - y}
sage: b = {x: 1 , y: 2}
sage: subs_all(a, b)
{'bar': -1, 'foo': 5}