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"""Square-free decomposition algorithms and related tools. """
from sympy.polys.densearith import (
dup_neg, dmp_neg,
dup_sub, dmp_sub,
dup_mul,
dup_quo, dmp_quo,
dup_mul_ground, dmp_mul_ground)
from sympy.polys.densebasic import (
dup_strip,
dup_LC, dmp_ground_LC,
dmp_zero_p,
dmp_ground,
dup_degree, dmp_degree,
dmp_raise, dmp_inject,
dup_convert)
from sympy.polys.densetools import (
dup_diff, dmp_diff, dmp_diff_in,
dup_shift, dmp_compose,
dup_monic, dmp_ground_monic,
dup_primitive, dmp_ground_primitive)
from sympy.polys.euclidtools import (
dup_inner_gcd, dmp_inner_gcd,
dup_gcd, dmp_gcd,
dmp_resultant)
from sympy.polys.galoistools import (
gf_sqf_list, gf_sqf_part)
from sympy.polys.polyerrors import (
MultivariatePolynomialError,
DomainError)
def dup_sqf_p(f, K):
"""
Return ``True`` if ``f`` is a square-free polynomial in ``K[x]``.
Examples
========
>>> from sympy.polys import ring, ZZ
>>> R, x = ring("x", ZZ)
>>> R.dup_sqf_p(x**2 - 2*x + 1)
False
>>> R.dup_sqf_p(x**2 - 1)
True
"""
if not f:
return True
else:
return not dup_degree(dup_gcd(f, dup_diff(f, 1, K), K))
def dmp_sqf_p(f, u, K):
"""
Return ``True`` if ``f`` is a square-free polynomial in ``K[X]``.
Examples
========
>>> from sympy.polys import ring, ZZ
>>> R, x,y = ring("x,y", ZZ)
>>> R.dmp_sqf_p(x**2 + 2*x*y + y**2)
False
>>> R.dmp_sqf_p(x**2 + y**2)
True
"""
if dmp_zero_p(f, u):
return True
else:
return not dmp_degree(dmp_gcd(f, dmp_diff(f, 1, u, K), u, K), u)
def dup_sqf_norm(f, K):
"""
Square-free norm of ``f`` in ``K[x]``, useful over algebraic domains.
Returns ``s``, ``f``, ``r``, such that ``g(x) = f(x-sa)`` and ``r(x) = Norm(g(x))``
is a square-free polynomial over K, where ``a`` is the algebraic extension of ``K``.
Examples
========
>>> from sympy.polys import ring, QQ
>>> from sympy import sqrt
>>> K = QQ.algebraic_field(sqrt(3))
>>> R, x = ring("x", K)
>>> _, X = ring("x", QQ)
>>> s, f, r = R.dup_sqf_norm(x**2 - 2)
>>> s == 1
True
>>> f == x**2 + K([QQ(-2), QQ(0)])*x + 1
True
>>> r == X**4 - 10*X**2 + 1
True
"""
if not K.is_Algebraic:
raise DomainError("ground domain must be algebraic")
s, g = 0, dmp_raise(K.mod.rep, 1, 0, K.dom)
while True:
h, _ = dmp_inject(f, 0, K, front=True)
r = dmp_resultant(g, h, 1, K.dom)
if dup_sqf_p(r, K.dom):
break
else:
f, s = dup_shift(f, -K.unit, K), s + 1
return s, f, r
def dmp_sqf_norm(f, u, K):
"""
Square-free norm of ``f`` in ``K[X]``, useful over algebraic domains.
Returns ``s``, ``f``, ``r``, such that ``g(x) = f(x-sa)`` and ``r(x) = Norm(g(x))``
is a square-free polynomial over K, where ``a`` is the algebraic extension of ``K``.
Examples
========
>>> from sympy.polys import ring, QQ
>>> from sympy import I
>>> K = QQ.algebraic_field(I)
>>> R, x, y = ring("x,y", K)
>>> _, X, Y = ring("x,y", QQ)
>>> s, f, r = R.dmp_sqf_norm(x*y + y**2)
>>> s == 1
True
>>> f == x*y + y**2 + K([QQ(-1), QQ(0)])*y
True
>>> r == X**2*Y**2 + 2*X*Y**3 + Y**4 + Y**2
True
"""
if not u:
return dup_sqf_norm(f, K)
if not K.is_Algebraic:
raise DomainError("ground domain must be algebraic")
g = dmp_raise(K.mod.rep, u + 1, 0, K.dom)
F = dmp_raise([K.one, -K.unit], u, 0, K)
s = 0
while True:
h, _ = dmp_inject(f, u, K, front=True)
r = dmp_resultant(g, h, u + 1, K.dom)
if dmp_sqf_p(r, u, K.dom):
break
else:
f, s = dmp_compose(f, F, u, K), s + 1
return s, f, r
def dmp_norm(f, u, K):
"""
Norm of ``f`` in ``K[X1, ..., Xn]``, often not square-free.
"""
if not K.is_Algebraic:
raise DomainError("ground domain must be algebraic")
g = dmp_raise(K.mod.rep, u + 1, 0, K.dom)
h, _ = dmp_inject(f, u, K, front=True)
return dmp_resultant(g, h, u + 1, K.dom)
def dup_gf_sqf_part(f, K):
"""Compute square-free part of ``f`` in ``GF(p)[x]``. """
f = dup_convert(f, K, K.dom)
g = gf_sqf_part(f, K.mod, K.dom)
return dup_convert(g, K.dom, K)
def dmp_gf_sqf_part(f, u, K):
"""Compute square-free part of ``f`` in ``GF(p)[X]``. """
raise NotImplementedError('multivariate polynomials over finite fields')
def dup_sqf_part(f, K):
"""
Returns square-free part of a polynomial in ``K[x]``.
Examples
========
>>> from sympy.polys import ring, ZZ
>>> R, x = ring("x", ZZ)
>>> R.dup_sqf_part(x**3 - 3*x - 2)
x**2 - x - 2
"""
if K.is_FiniteField:
return dup_gf_sqf_part(f, K)
if not f:
return f
if K.is_negative(dup_LC(f, K)):
f = dup_neg(f, K)
gcd = dup_gcd(f, dup_diff(f, 1, K), K)
sqf = dup_quo(f, gcd, K)
if K.is_Field:
return dup_monic(sqf, K)
else:
return dup_primitive(sqf, K)[1]
def dmp_sqf_part(f, u, K):
"""
Returns square-free part of a polynomial in ``K[X]``.
Examples
========
>>> from sympy.polys import ring, ZZ
>>> R, x,y = ring("x,y", ZZ)
>>> R.dmp_sqf_part(x**3 + 2*x**2*y + x*y**2)
x**2 + x*y
"""
if not u:
return dup_sqf_part(f, K)
if K.is_FiniteField:
return dmp_gf_sqf_part(f, u, K)
if dmp_zero_p(f, u):
return f
if K.is_negative(dmp_ground_LC(f, u, K)):
f = dmp_neg(f, u, K)
gcd = f
for i in range(u+1):
gcd = dmp_gcd(gcd, dmp_diff_in(f, 1, i, u, K), u, K)
sqf = dmp_quo(f, gcd, u, K)
if K.is_Field:
return dmp_ground_monic(sqf, u, K)
else:
return dmp_ground_primitive(sqf, u, K)[1]
def dup_gf_sqf_list(f, K, all=False):
"""Compute square-free decomposition of ``f`` in ``GF(p)[x]``. """
f = dup_convert(f, K, K.dom)
coeff, factors = gf_sqf_list(f, K.mod, K.dom, all=all)
for i, (f, k) in enumerate(factors):
factors[i] = (dup_convert(f, K.dom, K), k)
return K.convert(coeff, K.dom), factors
def dmp_gf_sqf_list(f, u, K, all=False):
"""Compute square-free decomposition of ``f`` in ``GF(p)[X]``. """
raise NotImplementedError('multivariate polynomials over finite fields')
def dup_sqf_list(f, K, all=False):
"""
Return square-free decomposition of a polynomial in ``K[x]``.
Examples
========
>>> from sympy.polys import ring, ZZ
>>> R, x = ring("x", ZZ)
>>> f = 2*x**5 + 16*x**4 + 50*x**3 + 76*x**2 + 56*x + 16
>>> R.dup_sqf_list(f)
(2, [(x + 1, 2), (x + 2, 3)])
>>> R.dup_sqf_list(f, all=True)
(2, [(1, 1), (x + 1, 2), (x + 2, 3)])
"""
if K.is_FiniteField:
return dup_gf_sqf_list(f, K, all=all)
if K.is_Field:
coeff = dup_LC(f, K)
f = dup_monic(f, K)
else:
coeff, f = dup_primitive(f, K)
if K.is_negative(dup_LC(f, K)):
f = dup_neg(f, K)
coeff = -coeff
if dup_degree(f) <= 0:
return coeff, []
result, i = [], 1
h = dup_diff(f, 1, K)
g, p, q = dup_inner_gcd(f, h, K)
while True:
d = dup_diff(p, 1, K)
h = dup_sub(q, d, K)
if not h:
result.append((p, i))
break
g, p, q = dup_inner_gcd(p, h, K)
if all or dup_degree(g) > 0:
result.append((g, i))
i += 1
return coeff, result
def dup_sqf_list_include(f, K, all=False):
"""
Return square-free decomposition of a polynomial in ``K[x]``.
Examples
========
>>> from sympy.polys import ring, ZZ
>>> R, x = ring("x", ZZ)
>>> f = 2*x**5 + 16*x**4 + 50*x**3 + 76*x**2 + 56*x + 16
>>> R.dup_sqf_list_include(f)
[(2, 1), (x + 1, 2), (x + 2, 3)]
>>> R.dup_sqf_list_include(f, all=True)
[(2, 1), (x + 1, 2), (x + 2, 3)]
"""
coeff, factors = dup_sqf_list(f, K, all=all)
if factors and factors[0][1] == 1:
g = dup_mul_ground(factors[0][0], coeff, K)
return [(g, 1)] + factors[1:]
else:
g = dup_strip([coeff])
return [(g, 1)] + factors
def dmp_sqf_list(f, u, K, all=False):
"""
Return square-free decomposition of a polynomial in ``K[X]``.
Examples
========
>>> from sympy.polys import ring, ZZ
>>> R, x,y = ring("x,y", ZZ)
>>> f = x**5 + 2*x**4*y + x**3*y**2
>>> R.dmp_sqf_list(f)
(1, [(x + y, 2), (x, 3)])
>>> R.dmp_sqf_list(f, all=True)
(1, [(1, 1), (x + y, 2), (x, 3)])
"""
if not u:
return dup_sqf_list(f, K, all=all)
if K.is_FiniteField:
return dmp_gf_sqf_list(f, u, K, all=all)
if K.is_Field:
coeff = dmp_ground_LC(f, u, K)
f = dmp_ground_monic(f, u, K)
else:
coeff, f = dmp_ground_primitive(f, u, K)
if K.is_negative(dmp_ground_LC(f, u, K)):
f = dmp_neg(f, u, K)
coeff = -coeff
if dmp_degree(f, u) <= 0:
return coeff, []
result, i = [], 1
h = dmp_diff(f, 1, u, K)
g, p, q = dmp_inner_gcd(f, h, u, K)
while True:
d = dmp_diff(p, 1, u, K)
h = dmp_sub(q, d, u, K)
if dmp_zero_p(h, u):
result.append((p, i))
break
g, p, q = dmp_inner_gcd(p, h, u, K)
if all or dmp_degree(g, u) > 0:
result.append((g, i))
i += 1
return coeff, result
def dmp_sqf_list_include(f, u, K, all=False):
"""
Return square-free decomposition of a polynomial in ``K[x]``.
Examples
========
>>> from sympy.polys import ring, ZZ
>>> R, x,y = ring("x,y", ZZ)
>>> f = x**5 + 2*x**4*y + x**3*y**2
>>> R.dmp_sqf_list_include(f)
[(1, 1), (x + y, 2), (x, 3)]
>>> R.dmp_sqf_list_include(f, all=True)
[(1, 1), (x + y, 2), (x, 3)]
"""
if not u:
return dup_sqf_list_include(f, K, all=all)
coeff, factors = dmp_sqf_list(f, u, K, all=all)
if factors and factors[0][1] == 1:
g = dmp_mul_ground(factors[0][0], coeff, u, K)
return [(g, 1)] + factors[1:]
else:
g = dmp_ground(coeff, u)
return [(g, 1)] + factors
def dup_gff_list(f, K):
"""
Compute greatest factorial factorization of ``f`` in ``K[x]``.
Examples
========
>>> from sympy.polys import ring, ZZ
>>> R, x = ring("x", ZZ)
>>> R.dup_gff_list(x**5 + 2*x**4 - x**3 - 2*x**2)
[(x, 1), (x + 2, 4)]
"""
if not f:
raise ValueError("greatest factorial factorization doesn't exist for a zero polynomial")
f = dup_monic(f, K)
if not dup_degree(f):
return []
else:
g = dup_gcd(f, dup_shift(f, K.one, K), K)
H = dup_gff_list(g, K)
for i, (h, k) in enumerate(H):
g = dup_mul(g, dup_shift(h, -K(k), K), K)
H[i] = (h, k + 1)
f = dup_quo(f, g, K)
if not dup_degree(f):
return H
else:
return [(f, 1)] + H
def dmp_gff_list(f, u, K):
"""
Compute greatest factorial factorization of ``f`` in ``K[X]``.
Examples
========
>>> from sympy.polys import ring, ZZ
>>> R, x,y = ring("x,y", ZZ)
"""
if not u:
return dup_gff_list(f, K)
else:
raise MultivariatePolynomialError(f)
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