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1503 lines
38 KiB
1503 lines
38 KiB
"""Polynomial factorization routines in characteristic zero. """
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from sympy.core.random import _randint
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from sympy.polys.galoistools import (
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gf_from_int_poly, gf_to_int_poly,
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gf_lshift, gf_add_mul, gf_mul,
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gf_div, gf_rem,
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gf_gcdex,
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gf_sqf_p,
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gf_factor_sqf, gf_factor)
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from sympy.polys.densebasic import (
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dup_LC, dmp_LC, dmp_ground_LC,
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dup_TC,
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dup_convert, dmp_convert,
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dup_degree, dmp_degree,
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dmp_degree_in, dmp_degree_list,
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dmp_from_dict,
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dmp_zero_p,
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dmp_one,
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dmp_nest, dmp_raise,
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dup_strip,
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dmp_ground,
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dup_inflate,
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dmp_exclude, dmp_include,
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dmp_inject, dmp_eject,
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dup_terms_gcd, dmp_terms_gcd)
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from sympy.polys.densearith import (
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dup_neg, dmp_neg,
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dup_add, dmp_add,
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dup_sub, dmp_sub,
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dup_mul, dmp_mul,
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dup_sqr,
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dmp_pow,
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dup_div, dmp_div,
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dup_quo, dmp_quo,
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dmp_expand,
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dmp_add_mul,
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dup_sub_mul, dmp_sub_mul,
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dup_lshift,
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dup_max_norm, dmp_max_norm,
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dup_l1_norm,
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dup_mul_ground, dmp_mul_ground,
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dup_quo_ground, dmp_quo_ground)
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from sympy.polys.densetools import (
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dup_clear_denoms, dmp_clear_denoms,
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dup_trunc, dmp_ground_trunc,
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dup_content,
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dup_monic, dmp_ground_monic,
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dup_primitive, dmp_ground_primitive,
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dmp_eval_tail,
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dmp_eval_in, dmp_diff_eval_in,
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dmp_compose,
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dup_shift, dup_mirror)
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from sympy.polys.euclidtools import (
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dmp_primitive,
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dup_inner_gcd, dmp_inner_gcd)
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from sympy.polys.sqfreetools import (
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dup_sqf_p,
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dup_sqf_norm, dmp_sqf_norm,
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dup_sqf_part, dmp_sqf_part)
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from sympy.polys.polyutils import _sort_factors
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from sympy.polys.polyconfig import query
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from sympy.polys.polyerrors import (
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ExtraneousFactors, DomainError, CoercionFailed, EvaluationFailed)
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from sympy.utilities import subsets
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from math import ceil as _ceil, log as _log
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def dup_trial_division(f, factors, K):
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"""
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Determine multiplicities of factors for a univariate polynomial
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using trial division.
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"""
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result = []
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for factor in factors:
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k = 0
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while True:
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q, r = dup_div(f, factor, K)
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if not r:
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f, k = q, k + 1
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else:
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break
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result.append((factor, k))
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return _sort_factors(result)
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def dmp_trial_division(f, factors, u, K):
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"""
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Determine multiplicities of factors for a multivariate polynomial
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using trial division.
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"""
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result = []
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for factor in factors:
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k = 0
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while True:
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q, r = dmp_div(f, factor, u, K)
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if dmp_zero_p(r, u):
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f, k = q, k + 1
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else:
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break
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result.append((factor, k))
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return _sort_factors(result)
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def dup_zz_mignotte_bound(f, K):
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"""
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The Knuth-Cohen variant of Mignotte bound for
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univariate polynomials in `K[x]`.
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Examples
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========
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>>> from sympy.polys import ring, ZZ
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>>> R, x = ring("x", ZZ)
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>>> f = x**3 + 14*x**2 + 56*x + 64
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>>> R.dup_zz_mignotte_bound(f)
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152
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By checking `factor(f)` we can see that max coeff is 8
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Also consider a case that `f` is irreducible for example `f = 2*x**2 + 3*x + 4`
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To avoid a bug for these cases, we return the bound plus the max coefficient of `f`
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>>> f = 2*x**2 + 3*x + 4
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>>> R.dup_zz_mignotte_bound(f)
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6
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Lastly,To see the difference between the new and the old Mignotte bound
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consider the irreducible polynomial::
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>>> f = 87*x**7 + 4*x**6 + 80*x**5 + 17*x**4 + 9*x**3 + 12*x**2 + 49*x + 26
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>>> R.dup_zz_mignotte_bound(f)
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744
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The new Mignotte bound is 744 whereas the old one (SymPy 1.5.1) is 1937664.
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References
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==========
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..[1] [Abbott2013]_
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"""
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from sympy.functions.combinatorial.factorials import binomial
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d = dup_degree(f)
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delta = _ceil(d / 2)
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delta2 = _ceil(delta / 2)
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# euclidean-norm
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eucl_norm = K.sqrt( sum( [cf**2 for cf in f] ) )
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# biggest values of binomial coefficients (p. 538 of reference)
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t1 = binomial(delta - 1, delta2)
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t2 = binomial(delta - 1, delta2 - 1)
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lc = K.abs(dup_LC(f, K)) # leading coefficient
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bound = t1 * eucl_norm + t2 * lc # (p. 538 of reference)
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bound += dup_max_norm(f, K) # add max coeff for irreducible polys
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bound = _ceil(bound / 2) * 2 # round up to even integer
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return bound
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def dmp_zz_mignotte_bound(f, u, K):
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"""Mignotte bound for multivariate polynomials in `K[X]`. """
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a = dmp_max_norm(f, u, K)
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b = abs(dmp_ground_LC(f, u, K))
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n = sum(dmp_degree_list(f, u))
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return K.sqrt(K(n + 1))*2**n*a*b
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def dup_zz_hensel_step(m, f, g, h, s, t, K):
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"""
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One step in Hensel lifting in `Z[x]`.
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Given positive integer `m` and `Z[x]` polynomials `f`, `g`, `h`, `s`
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and `t` such that::
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f = g*h (mod m)
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s*g + t*h = 1 (mod m)
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lc(f) is not a zero divisor (mod m)
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lc(h) = 1
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deg(f) = deg(g) + deg(h)
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deg(s) < deg(h)
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deg(t) < deg(g)
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returns polynomials `G`, `H`, `S` and `T`, such that::
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f = G*H (mod m**2)
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S*G + T*H = 1 (mod m**2)
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References
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==========
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.. [1] [Gathen99]_
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"""
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M = m**2
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e = dup_sub_mul(f, g, h, K)
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e = dup_trunc(e, M, K)
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q, r = dup_div(dup_mul(s, e, K), h, K)
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q = dup_trunc(q, M, K)
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r = dup_trunc(r, M, K)
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u = dup_add(dup_mul(t, e, K), dup_mul(q, g, K), K)
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G = dup_trunc(dup_add(g, u, K), M, K)
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H = dup_trunc(dup_add(h, r, K), M, K)
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u = dup_add(dup_mul(s, G, K), dup_mul(t, H, K), K)
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b = dup_trunc(dup_sub(u, [K.one], K), M, K)
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c, d = dup_div(dup_mul(s, b, K), H, K)
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c = dup_trunc(c, M, K)
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d = dup_trunc(d, M, K)
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u = dup_add(dup_mul(t, b, K), dup_mul(c, G, K), K)
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S = dup_trunc(dup_sub(s, d, K), M, K)
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T = dup_trunc(dup_sub(t, u, K), M, K)
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return G, H, S, T
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def dup_zz_hensel_lift(p, f, f_list, l, K):
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r"""
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Multifactor Hensel lifting in `Z[x]`.
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Given a prime `p`, polynomial `f` over `Z[x]` such that `lc(f)`
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is a unit modulo `p`, monic pair-wise coprime polynomials `f_i`
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over `Z[x]` satisfying::
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f = lc(f) f_1 ... f_r (mod p)
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and a positive integer `l`, returns a list of monic polynomials
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`F_1,\ F_2,\ \dots,\ F_r` satisfying::
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f = lc(f) F_1 ... F_r (mod p**l)
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F_i = f_i (mod p), i = 1..r
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References
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==========
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.. [1] [Gathen99]_
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"""
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r = len(f_list)
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lc = dup_LC(f, K)
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if r == 1:
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F = dup_mul_ground(f, K.gcdex(lc, p**l)[0], K)
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return [ dup_trunc(F, p**l, K) ]
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m = p
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k = r // 2
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d = int(_ceil(_log(l, 2)))
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g = gf_from_int_poly([lc], p)
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for f_i in f_list[:k]:
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g = gf_mul(g, gf_from_int_poly(f_i, p), p, K)
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h = gf_from_int_poly(f_list[k], p)
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for f_i in f_list[k + 1:]:
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h = gf_mul(h, gf_from_int_poly(f_i, p), p, K)
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s, t, _ = gf_gcdex(g, h, p, K)
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g = gf_to_int_poly(g, p)
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h = gf_to_int_poly(h, p)
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s = gf_to_int_poly(s, p)
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t = gf_to_int_poly(t, p)
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for _ in range(1, d + 1):
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(g, h, s, t), m = dup_zz_hensel_step(m, f, g, h, s, t, K), m**2
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return dup_zz_hensel_lift(p, g, f_list[:k], l, K) \
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+ dup_zz_hensel_lift(p, h, f_list[k:], l, K)
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def _test_pl(fc, q, pl):
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if q > pl // 2:
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q = q - pl
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if not q:
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return True
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return fc % q == 0
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def dup_zz_zassenhaus(f, K):
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"""Factor primitive square-free polynomials in `Z[x]`. """
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n = dup_degree(f)
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if n == 1:
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return [f]
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from sympy.ntheory import isprime
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fc = f[-1]
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A = dup_max_norm(f, K)
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b = dup_LC(f, K)
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B = int(abs(K.sqrt(K(n + 1))*2**n*A*b))
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C = int((n + 1)**(2*n)*A**(2*n - 1))
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gamma = int(_ceil(2*_log(C, 2)))
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bound = int(2*gamma*_log(gamma))
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a = []
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# choose a prime number `p` such that `f` be square free in Z_p
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# if there are many factors in Z_p, choose among a few different `p`
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# the one with fewer factors
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for px in range(3, bound + 1):
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if not isprime(px) or b % px == 0:
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continue
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px = K.convert(px)
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F = gf_from_int_poly(f, px)
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if not gf_sqf_p(F, px, K):
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continue
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fsqfx = gf_factor_sqf(F, px, K)[1]
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a.append((px, fsqfx))
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if len(fsqfx) < 15 or len(a) > 4:
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break
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p, fsqf = min(a, key=lambda x: len(x[1]))
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l = int(_ceil(_log(2*B + 1, p)))
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modular = [gf_to_int_poly(ff, p) for ff in fsqf]
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g = dup_zz_hensel_lift(p, f, modular, l, K)
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sorted_T = range(len(g))
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T = set(sorted_T)
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factors, s = [], 1
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pl = p**l
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while 2*s <= len(T):
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for S in subsets(sorted_T, s):
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# lift the constant coefficient of the product `G` of the factors
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# in the subset `S`; if it is does not divide `fc`, `G` does
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# not divide the input polynomial
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if b == 1:
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q = 1
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for i in S:
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q = q*g[i][-1]
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q = q % pl
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if not _test_pl(fc, q, pl):
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continue
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else:
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G = [b]
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for i in S:
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G = dup_mul(G, g[i], K)
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G = dup_trunc(G, pl, K)
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G = dup_primitive(G, K)[1]
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q = G[-1]
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if q and fc % q != 0:
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continue
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H = [b]
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S = set(S)
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T_S = T - S
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if b == 1:
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G = [b]
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for i in S:
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G = dup_mul(G, g[i], K)
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G = dup_trunc(G, pl, K)
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for i in T_S:
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H = dup_mul(H, g[i], K)
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H = dup_trunc(H, pl, K)
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G_norm = dup_l1_norm(G, K)
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H_norm = dup_l1_norm(H, K)
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if G_norm*H_norm <= B:
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T = T_S
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sorted_T = [i for i in sorted_T if i not in S]
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G = dup_primitive(G, K)[1]
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f = dup_primitive(H, K)[1]
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factors.append(G)
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b = dup_LC(f, K)
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break
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else:
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s += 1
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return factors + [f]
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def dup_zz_irreducible_p(f, K):
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"""Test irreducibility using Eisenstein's criterion. """
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lc = dup_LC(f, K)
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tc = dup_TC(f, K)
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e_fc = dup_content(f[1:], K)
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if e_fc:
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from sympy.ntheory import factorint
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e_ff = factorint(int(e_fc))
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for p in e_ff.keys():
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if (lc % p) and (tc % p**2):
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return True
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def dup_cyclotomic_p(f, K, irreducible=False):
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"""
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Efficiently test if ``f`` is a cyclotomic polynomial.
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Examples
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========
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>>> from sympy.polys import ring, ZZ
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>>> R, x = ring("x", ZZ)
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>>> f = x**16 + x**14 - x**10 + x**8 - x**6 + x**2 + 1
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>>> R.dup_cyclotomic_p(f)
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False
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>>> g = x**16 + x**14 - x**10 - x**8 - x**6 + x**2 + 1
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>>> R.dup_cyclotomic_p(g)
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True
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References
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==========
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Bradford, Russell J., and James H. Davenport. "Effective tests for
|
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cyclotomic polynomials." In International Symposium on Symbolic and
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Algebraic Computation, pp. 244-251. Springer, Berlin, Heidelberg, 1988.
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"""
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if K.is_QQ:
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try:
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K0, K = K, K.get_ring()
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f = dup_convert(f, K0, K)
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except CoercionFailed:
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return False
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elif not K.is_ZZ:
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return False
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lc = dup_LC(f, K)
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tc = dup_TC(f, K)
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if lc != 1 or (tc != -1 and tc != 1):
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return False
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if not irreducible:
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coeff, factors = dup_factor_list(f, K)
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if coeff != K.one or factors != [(f, 1)]:
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return False
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n = dup_degree(f)
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g, h = [], []
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for i in range(n, -1, -2):
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g.insert(0, f[i])
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for i in range(n - 1, -1, -2):
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h.insert(0, f[i])
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g = dup_sqr(dup_strip(g), K)
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h = dup_sqr(dup_strip(h), K)
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F = dup_sub(g, dup_lshift(h, 1, K), K)
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if K.is_negative(dup_LC(F, K)):
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F = dup_neg(F, K)
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if F == f:
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return True
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g = dup_mirror(f, K)
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if K.is_negative(dup_LC(g, K)):
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g = dup_neg(g, K)
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if F == g and dup_cyclotomic_p(g, K):
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return True
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G = dup_sqf_part(F, K)
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if dup_sqr(G, K) == F and dup_cyclotomic_p(G, K):
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return True
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return False
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def dup_zz_cyclotomic_poly(n, K):
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"""Efficiently generate n-th cyclotomic polynomial. """
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|
from sympy.ntheory import factorint
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h = [K.one, -K.one]
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|
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for p, k in factorint(n).items():
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h = dup_quo(dup_inflate(h, p, K), h, K)
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h = dup_inflate(h, p**(k - 1), K)
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return h
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|
|
def _dup_cyclotomic_decompose(n, K):
|
|
from sympy.ntheory import factorint
|
|
|
|
H = [[K.one, -K.one]]
|
|
|
|
for p, k in factorint(n).items():
|
|
Q = [ dup_quo(dup_inflate(h, p, K), h, K) for h in H ]
|
|
H.extend(Q)
|
|
|
|
for i in range(1, k):
|
|
Q = [ dup_inflate(q, p, K) for q in Q ]
|
|
H.extend(Q)
|
|
|
|
return H
|
|
|
|
|
|
def dup_zz_cyclotomic_factor(f, K):
|
|
"""
|
|
Efficiently factor polynomials `x**n - 1` and `x**n + 1` in `Z[x]`.
|
|
|
|
Given a univariate polynomial `f` in `Z[x]` returns a list of factors
|
|
of `f`, provided that `f` is in the form `x**n - 1` or `x**n + 1` for
|
|
`n >= 1`. Otherwise returns None.
|
|
|
|
Factorization is performed using cyclotomic decomposition of `f`,
|
|
which makes this method much faster that any other direct factorization
|
|
approach (e.g. Zassenhaus's).
|
|
|
|
References
|
|
==========
|
|
|
|
.. [1] [Weisstein09]_
|
|
|
|
"""
|
|
lc_f, tc_f = dup_LC(f, K), dup_TC(f, K)
|
|
|
|
if dup_degree(f) <= 0:
|
|
return None
|
|
|
|
if lc_f != 1 or tc_f not in [-1, 1]:
|
|
return None
|
|
|
|
if any(bool(cf) for cf in f[1:-1]):
|
|
return None
|
|
|
|
n = dup_degree(f)
|
|
F = _dup_cyclotomic_decompose(n, K)
|
|
|
|
if not K.is_one(tc_f):
|
|
return F
|
|
else:
|
|
H = []
|
|
|
|
for h in _dup_cyclotomic_decompose(2*n, K):
|
|
if h not in F:
|
|
H.append(h)
|
|
|
|
return H
|
|
|
|
|
|
def dup_zz_factor_sqf(f, K):
|
|
"""Factor square-free (non-primitive) polynomials in `Z[x]`. """
|
|
cont, g = dup_primitive(f, K)
|
|
|
|
n = dup_degree(g)
|
|
|
|
if dup_LC(g, K) < 0:
|
|
cont, g = -cont, dup_neg(g, K)
|
|
|
|
if n <= 0:
|
|
return cont, []
|
|
elif n == 1:
|
|
return cont, [g]
|
|
|
|
if query('USE_IRREDUCIBLE_IN_FACTOR'):
|
|
if dup_zz_irreducible_p(g, K):
|
|
return cont, [g]
|
|
|
|
factors = None
|
|
|
|
if query('USE_CYCLOTOMIC_FACTOR'):
|
|
factors = dup_zz_cyclotomic_factor(g, K)
|
|
|
|
if factors is None:
|
|
factors = dup_zz_zassenhaus(g, K)
|
|
|
|
return cont, _sort_factors(factors, multiple=False)
|
|
|
|
|
|
def dup_zz_factor(f, K):
|
|
"""
|
|
Factor (non square-free) polynomials in `Z[x]`.
|
|
|
|
Given a univariate polynomial `f` in `Z[x]` computes its complete
|
|
factorization `f_1, ..., f_n` into irreducibles over integers::
|
|
|
|
f = content(f) f_1**k_1 ... f_n**k_n
|
|
|
|
The factorization is computed by reducing the input polynomial
|
|
into a primitive square-free polynomial and factoring it using
|
|
Zassenhaus algorithm. Trial division is used to recover the
|
|
multiplicities of factors.
|
|
|
|
The result is returned as a tuple consisting of::
|
|
|
|
(content(f), [(f_1, k_1), ..., (f_n, k_n))
|
|
|
|
Examples
|
|
========
|
|
|
|
Consider the polynomial `f = 2*x**4 - 2`::
|
|
|
|
>>> from sympy.polys import ring, ZZ
|
|
>>> R, x = ring("x", ZZ)
|
|
|
|
>>> R.dup_zz_factor(2*x**4 - 2)
|
|
(2, [(x - 1, 1), (x + 1, 1), (x**2 + 1, 1)])
|
|
|
|
In result we got the following factorization::
|
|
|
|
f = 2 (x - 1) (x + 1) (x**2 + 1)
|
|
|
|
Note that this is a complete factorization over integers,
|
|
however over Gaussian integers we can factor the last term.
|
|
|
|
By default, polynomials `x**n - 1` and `x**n + 1` are factored
|
|
using cyclotomic decomposition to speedup computations. To
|
|
disable this behaviour set cyclotomic=False.
|
|
|
|
References
|
|
==========
|
|
|
|
.. [1] [Gathen99]_
|
|
|
|
"""
|
|
cont, g = dup_primitive(f, K)
|
|
|
|
n = dup_degree(g)
|
|
|
|
if dup_LC(g, K) < 0:
|
|
cont, g = -cont, dup_neg(g, K)
|
|
|
|
if n <= 0:
|
|
return cont, []
|
|
elif n == 1:
|
|
return cont, [(g, 1)]
|
|
|
|
if query('USE_IRREDUCIBLE_IN_FACTOR'):
|
|
if dup_zz_irreducible_p(g, K):
|
|
return cont, [(g, 1)]
|
|
|
|
g = dup_sqf_part(g, K)
|
|
H = None
|
|
|
|
if query('USE_CYCLOTOMIC_FACTOR'):
|
|
H = dup_zz_cyclotomic_factor(g, K)
|
|
|
|
if H is None:
|
|
H = dup_zz_zassenhaus(g, K)
|
|
|
|
factors = dup_trial_division(f, H, K)
|
|
return cont, factors
|
|
|
|
|
|
def dmp_zz_wang_non_divisors(E, cs, ct, K):
|
|
"""Wang/EEZ: Compute a set of valid divisors. """
|
|
result = [ cs*ct ]
|
|
|
|
for q in E:
|
|
q = abs(q)
|
|
|
|
for r in reversed(result):
|
|
while r != 1:
|
|
r = K.gcd(r, q)
|
|
q = q // r
|
|
|
|
if K.is_one(q):
|
|
return None
|
|
|
|
result.append(q)
|
|
|
|
return result[1:]
|
|
|
|
|
|
def dmp_zz_wang_test_points(f, T, ct, A, u, K):
|
|
"""Wang/EEZ: Test evaluation points for suitability. """
|
|
if not dmp_eval_tail(dmp_LC(f, K), A, u - 1, K):
|
|
raise EvaluationFailed('no luck')
|
|
|
|
g = dmp_eval_tail(f, A, u, K)
|
|
|
|
if not dup_sqf_p(g, K):
|
|
raise EvaluationFailed('no luck')
|
|
|
|
c, h = dup_primitive(g, K)
|
|
|
|
if K.is_negative(dup_LC(h, K)):
|
|
c, h = -c, dup_neg(h, K)
|
|
|
|
v = u - 1
|
|
|
|
E = [ dmp_eval_tail(t, A, v, K) for t, _ in T ]
|
|
D = dmp_zz_wang_non_divisors(E, c, ct, K)
|
|
|
|
if D is not None:
|
|
return c, h, E
|
|
else:
|
|
raise EvaluationFailed('no luck')
|
|
|
|
|
|
def dmp_zz_wang_lead_coeffs(f, T, cs, E, H, A, u, K):
|
|
"""Wang/EEZ: Compute correct leading coefficients. """
|
|
C, J, v = [], [0]*len(E), u - 1
|
|
|
|
for h in H:
|
|
c = dmp_one(v, K)
|
|
d = dup_LC(h, K)*cs
|
|
|
|
for i in reversed(range(len(E))):
|
|
k, e, (t, _) = 0, E[i], T[i]
|
|
|
|
while not (d % e):
|
|
d, k = d//e, k + 1
|
|
|
|
if k != 0:
|
|
c, J[i] = dmp_mul(c, dmp_pow(t, k, v, K), v, K), 1
|
|
|
|
C.append(c)
|
|
|
|
if not all(J):
|
|
raise ExtraneousFactors # pragma: no cover
|
|
|
|
CC, HH = [], []
|
|
|
|
for c, h in zip(C, H):
|
|
d = dmp_eval_tail(c, A, v, K)
|
|
lc = dup_LC(h, K)
|
|
|
|
if K.is_one(cs):
|
|
cc = lc//d
|
|
else:
|
|
g = K.gcd(lc, d)
|
|
d, cc = d//g, lc//g
|
|
h, cs = dup_mul_ground(h, d, K), cs//d
|
|
|
|
c = dmp_mul_ground(c, cc, v, K)
|
|
|
|
CC.append(c)
|
|
HH.append(h)
|
|
|
|
if K.is_one(cs):
|
|
return f, HH, CC
|
|
|
|
CCC, HHH = [], []
|
|
|
|
for c, h in zip(CC, HH):
|
|
CCC.append(dmp_mul_ground(c, cs, v, K))
|
|
HHH.append(dmp_mul_ground(h, cs, 0, K))
|
|
|
|
f = dmp_mul_ground(f, cs**(len(H) - 1), u, K)
|
|
|
|
return f, HHH, CCC
|
|
|
|
|
|
def dup_zz_diophantine(F, m, p, K):
|
|
"""Wang/EEZ: Solve univariate Diophantine equations. """
|
|
if len(F) == 2:
|
|
a, b = F
|
|
|
|
f = gf_from_int_poly(a, p)
|
|
g = gf_from_int_poly(b, p)
|
|
|
|
s, t, G = gf_gcdex(g, f, p, K)
|
|
|
|
s = gf_lshift(s, m, K)
|
|
t = gf_lshift(t, m, K)
|
|
|
|
q, s = gf_div(s, f, p, K)
|
|
|
|
t = gf_add_mul(t, q, g, p, K)
|
|
|
|
s = gf_to_int_poly(s, p)
|
|
t = gf_to_int_poly(t, p)
|
|
|
|
result = [s, t]
|
|
else:
|
|
G = [F[-1]]
|
|
|
|
for f in reversed(F[1:-1]):
|
|
G.insert(0, dup_mul(f, G[0], K))
|
|
|
|
S, T = [], [[1]]
|
|
|
|
for f, g in zip(F, G):
|
|
t, s = dmp_zz_diophantine([g, f], T[-1], [], 0, p, 1, K)
|
|
T.append(t)
|
|
S.append(s)
|
|
|
|
result, S = [], S + [T[-1]]
|
|
|
|
for s, f in zip(S, F):
|
|
s = gf_from_int_poly(s, p)
|
|
f = gf_from_int_poly(f, p)
|
|
|
|
r = gf_rem(gf_lshift(s, m, K), f, p, K)
|
|
s = gf_to_int_poly(r, p)
|
|
|
|
result.append(s)
|
|
|
|
return result
|
|
|
|
|
|
def dmp_zz_diophantine(F, c, A, d, p, u, K):
|
|
"""Wang/EEZ: Solve multivariate Diophantine equations. """
|
|
if not A:
|
|
S = [ [] for _ in F ]
|
|
n = dup_degree(c)
|
|
|
|
for i, coeff in enumerate(c):
|
|
if not coeff:
|
|
continue
|
|
|
|
T = dup_zz_diophantine(F, n - i, p, K)
|
|
|
|
for j, (s, t) in enumerate(zip(S, T)):
|
|
t = dup_mul_ground(t, coeff, K)
|
|
S[j] = dup_trunc(dup_add(s, t, K), p, K)
|
|
else:
|
|
n = len(A)
|
|
e = dmp_expand(F, u, K)
|
|
|
|
a, A = A[-1], A[:-1]
|
|
B, G = [], []
|
|
|
|
for f in F:
|
|
B.append(dmp_quo(e, f, u, K))
|
|
G.append(dmp_eval_in(f, a, n, u, K))
|
|
|
|
C = dmp_eval_in(c, a, n, u, K)
|
|
|
|
v = u - 1
|
|
|
|
S = dmp_zz_diophantine(G, C, A, d, p, v, K)
|
|
S = [ dmp_raise(s, 1, v, K) for s in S ]
|
|
|
|
for s, b in zip(S, B):
|
|
c = dmp_sub_mul(c, s, b, u, K)
|
|
|
|
c = dmp_ground_trunc(c, p, u, K)
|
|
|
|
m = dmp_nest([K.one, -a], n, K)
|
|
M = dmp_one(n, K)
|
|
|
|
for k in K.map(range(0, d)):
|
|
if dmp_zero_p(c, u):
|
|
break
|
|
|
|
M = dmp_mul(M, m, u, K)
|
|
C = dmp_diff_eval_in(c, k + 1, a, n, u, K)
|
|
|
|
if not dmp_zero_p(C, v):
|
|
C = dmp_quo_ground(C, K.factorial(k + 1), v, K)
|
|
T = dmp_zz_diophantine(G, C, A, d, p, v, K)
|
|
|
|
for i, t in enumerate(T):
|
|
T[i] = dmp_mul(dmp_raise(t, 1, v, K), M, u, K)
|
|
|
|
for i, (s, t) in enumerate(zip(S, T)):
|
|
S[i] = dmp_add(s, t, u, K)
|
|
|
|
for t, b in zip(T, B):
|
|
c = dmp_sub_mul(c, t, b, u, K)
|
|
|
|
c = dmp_ground_trunc(c, p, u, K)
|
|
|
|
S = [ dmp_ground_trunc(s, p, u, K) for s in S ]
|
|
|
|
return S
|
|
|
|
|
|
def dmp_zz_wang_hensel_lifting(f, H, LC, A, p, u, K):
|
|
"""Wang/EEZ: Parallel Hensel lifting algorithm. """
|
|
S, n, v = [f], len(A), u - 1
|
|
|
|
H = list(H)
|
|
|
|
for i, a in enumerate(reversed(A[1:])):
|
|
s = dmp_eval_in(S[0], a, n - i, u - i, K)
|
|
S.insert(0, dmp_ground_trunc(s, p, v - i, K))
|
|
|
|
d = max(dmp_degree_list(f, u)[1:])
|
|
|
|
for j, s, a in zip(range(2, n + 2), S, A):
|
|
G, w = list(H), j - 1
|
|
|
|
I, J = A[:j - 2], A[j - 1:]
|
|
|
|
for i, (h, lc) in enumerate(zip(H, LC)):
|
|
lc = dmp_ground_trunc(dmp_eval_tail(lc, J, v, K), p, w - 1, K)
|
|
H[i] = [lc] + dmp_raise(h[1:], 1, w - 1, K)
|
|
|
|
m = dmp_nest([K.one, -a], w, K)
|
|
M = dmp_one(w, K)
|
|
|
|
c = dmp_sub(s, dmp_expand(H, w, K), w, K)
|
|
|
|
dj = dmp_degree_in(s, w, w)
|
|
|
|
for k in K.map(range(0, dj)):
|
|
if dmp_zero_p(c, w):
|
|
break
|
|
|
|
M = dmp_mul(M, m, w, K)
|
|
C = dmp_diff_eval_in(c, k + 1, a, w, w, K)
|
|
|
|
if not dmp_zero_p(C, w - 1):
|
|
C = dmp_quo_ground(C, K.factorial(k + 1), w - 1, K)
|
|
T = dmp_zz_diophantine(G, C, I, d, p, w - 1, K)
|
|
|
|
for i, (h, t) in enumerate(zip(H, T)):
|
|
h = dmp_add_mul(h, dmp_raise(t, 1, w - 1, K), M, w, K)
|
|
H[i] = dmp_ground_trunc(h, p, w, K)
|
|
|
|
h = dmp_sub(s, dmp_expand(H, w, K), w, K)
|
|
c = dmp_ground_trunc(h, p, w, K)
|
|
|
|
if dmp_expand(H, u, K) != f:
|
|
raise ExtraneousFactors # pragma: no cover
|
|
else:
|
|
return H
|
|
|
|
|
|
def dmp_zz_wang(f, u, K, mod=None, seed=None):
|
|
r"""
|
|
Factor primitive square-free polynomials in `Z[X]`.
|
|
|
|
Given a multivariate polynomial `f` in `Z[x_1,...,x_n]`, which is
|
|
primitive and square-free in `x_1`, computes factorization of `f` into
|
|
irreducibles over integers.
|
|
|
|
The procedure is based on Wang's Enhanced Extended Zassenhaus
|
|
algorithm. The algorithm works by viewing `f` as a univariate polynomial
|
|
in `Z[x_2,...,x_n][x_1]`, for which an evaluation mapping is computed::
|
|
|
|
x_2 -> a_2, ..., x_n -> a_n
|
|
|
|
where `a_i`, for `i = 2, \dots, n`, are carefully chosen integers. The
|
|
mapping is used to transform `f` into a univariate polynomial in `Z[x_1]`,
|
|
which can be factored efficiently using Zassenhaus algorithm. The last
|
|
step is to lift univariate factors to obtain true multivariate
|
|
factors. For this purpose a parallel Hensel lifting procedure is used.
|
|
|
|
The parameter ``seed`` is passed to _randint and can be used to seed randint
|
|
(when an integer) or (for testing purposes) can be a sequence of numbers.
|
|
|
|
References
|
|
==========
|
|
|
|
.. [1] [Wang78]_
|
|
.. [2] [Geddes92]_
|
|
|
|
"""
|
|
from sympy.ntheory import nextprime
|
|
|
|
randint = _randint(seed)
|
|
|
|
ct, T = dmp_zz_factor(dmp_LC(f, K), u - 1, K)
|
|
|
|
b = dmp_zz_mignotte_bound(f, u, K)
|
|
p = K(nextprime(b))
|
|
|
|
if mod is None:
|
|
if u == 1:
|
|
mod = 2
|
|
else:
|
|
mod = 1
|
|
|
|
history, configs, A, r = set(), [], [K.zero]*u, None
|
|
|
|
try:
|
|
cs, s, E = dmp_zz_wang_test_points(f, T, ct, A, u, K)
|
|
|
|
_, H = dup_zz_factor_sqf(s, K)
|
|
|
|
r = len(H)
|
|
|
|
if r == 1:
|
|
return [f]
|
|
|
|
configs = [(s, cs, E, H, A)]
|
|
except EvaluationFailed:
|
|
pass
|
|
|
|
eez_num_configs = query('EEZ_NUMBER_OF_CONFIGS')
|
|
eez_num_tries = query('EEZ_NUMBER_OF_TRIES')
|
|
eez_mod_step = query('EEZ_MODULUS_STEP')
|
|
|
|
while len(configs) < eez_num_configs:
|
|
for _ in range(eez_num_tries):
|
|
A = [ K(randint(-mod, mod)) for _ in range(u) ]
|
|
|
|
if tuple(A) not in history:
|
|
history.add(tuple(A))
|
|
else:
|
|
continue
|
|
|
|
try:
|
|
cs, s, E = dmp_zz_wang_test_points(f, T, ct, A, u, K)
|
|
except EvaluationFailed:
|
|
continue
|
|
|
|
_, H = dup_zz_factor_sqf(s, K)
|
|
|
|
rr = len(H)
|
|
|
|
if r is not None:
|
|
if rr != r: # pragma: no cover
|
|
if rr < r:
|
|
configs, r = [], rr
|
|
else:
|
|
continue
|
|
else:
|
|
r = rr
|
|
|
|
if r == 1:
|
|
return [f]
|
|
|
|
configs.append((s, cs, E, H, A))
|
|
|
|
if len(configs) == eez_num_configs:
|
|
break
|
|
else:
|
|
mod += eez_mod_step
|
|
|
|
s_norm, s_arg, i = None, 0, 0
|
|
|
|
for s, _, _, _, _ in configs:
|
|
_s_norm = dup_max_norm(s, K)
|
|
|
|
if s_norm is not None:
|
|
if _s_norm < s_norm:
|
|
s_norm = _s_norm
|
|
s_arg = i
|
|
else:
|
|
s_norm = _s_norm
|
|
|
|
i += 1
|
|
|
|
_, cs, E, H, A = configs[s_arg]
|
|
orig_f = f
|
|
|
|
try:
|
|
f, H, LC = dmp_zz_wang_lead_coeffs(f, T, cs, E, H, A, u, K)
|
|
factors = dmp_zz_wang_hensel_lifting(f, H, LC, A, p, u, K)
|
|
except ExtraneousFactors: # pragma: no cover
|
|
if query('EEZ_RESTART_IF_NEEDED'):
|
|
return dmp_zz_wang(orig_f, u, K, mod + 1)
|
|
else:
|
|
raise ExtraneousFactors(
|
|
"we need to restart algorithm with better parameters")
|
|
|
|
result = []
|
|
|
|
for f in factors:
|
|
_, f = dmp_ground_primitive(f, u, K)
|
|
|
|
if K.is_negative(dmp_ground_LC(f, u, K)):
|
|
f = dmp_neg(f, u, K)
|
|
|
|
result.append(f)
|
|
|
|
return result
|
|
|
|
|
|
def dmp_zz_factor(f, u, K):
|
|
r"""
|
|
Factor (non square-free) polynomials in `Z[X]`.
|
|
|
|
Given a multivariate polynomial `f` in `Z[x]` computes its complete
|
|
factorization `f_1, \dots, f_n` into irreducibles over integers::
|
|
|
|
f = content(f) f_1**k_1 ... f_n**k_n
|
|
|
|
The factorization is computed by reducing the input polynomial
|
|
into a primitive square-free polynomial and factoring it using
|
|
Enhanced Extended Zassenhaus (EEZ) algorithm. Trial division
|
|
is used to recover the multiplicities of factors.
|
|
|
|
The result is returned as a tuple consisting of::
|
|
|
|
(content(f), [(f_1, k_1), ..., (f_n, k_n))
|
|
|
|
Consider polynomial `f = 2*(x**2 - y**2)`::
|
|
|
|
>>> from sympy.polys import ring, ZZ
|
|
>>> R, x,y = ring("x,y", ZZ)
|
|
|
|
>>> R.dmp_zz_factor(2*x**2 - 2*y**2)
|
|
(2, [(x - y, 1), (x + y, 1)])
|
|
|
|
In result we got the following factorization::
|
|
|
|
f = 2 (x - y) (x + y)
|
|
|
|
References
|
|
==========
|
|
|
|
.. [1] [Gathen99]_
|
|
|
|
"""
|
|
if not u:
|
|
return dup_zz_factor(f, K)
|
|
|
|
if dmp_zero_p(f, u):
|
|
return K.zero, []
|
|
|
|
cont, g = dmp_ground_primitive(f, u, K)
|
|
|
|
if dmp_ground_LC(g, u, K) < 0:
|
|
cont, g = -cont, dmp_neg(g, u, K)
|
|
|
|
if all(d <= 0 for d in dmp_degree_list(g, u)):
|
|
return cont, []
|
|
|
|
G, g = dmp_primitive(g, u, K)
|
|
|
|
factors = []
|
|
|
|
if dmp_degree(g, u) > 0:
|
|
g = dmp_sqf_part(g, u, K)
|
|
H = dmp_zz_wang(g, u, K)
|
|
factors = dmp_trial_division(f, H, u, K)
|
|
|
|
for g, k in dmp_zz_factor(G, u - 1, K)[1]:
|
|
factors.insert(0, ([g], k))
|
|
|
|
return cont, _sort_factors(factors)
|
|
|
|
|
|
def dup_qq_i_factor(f, K0):
|
|
"""Factor univariate polynomials into irreducibles in `QQ_I[x]`. """
|
|
# Factor in QQ<I>
|
|
K1 = K0.as_AlgebraicField()
|
|
f = dup_convert(f, K0, K1)
|
|
coeff, factors = dup_factor_list(f, K1)
|
|
factors = [(dup_convert(fac, K1, K0), i) for fac, i in factors]
|
|
coeff = K0.convert(coeff, K1)
|
|
return coeff, factors
|
|
|
|
|
|
def dup_zz_i_factor(f, K0):
|
|
"""Factor univariate polynomials into irreducibles in `ZZ_I[x]`. """
|
|
# First factor in QQ_I
|
|
K1 = K0.get_field()
|
|
f = dup_convert(f, K0, K1)
|
|
coeff, factors = dup_qq_i_factor(f, K1)
|
|
|
|
new_factors = []
|
|
for fac, i in factors:
|
|
# Extract content
|
|
fac_denom, fac_num = dup_clear_denoms(fac, K1)
|
|
fac_num_ZZ_I = dup_convert(fac_num, K1, K0)
|
|
content, fac_prim = dmp_ground_primitive(fac_num_ZZ_I, 0, K1)
|
|
|
|
coeff = (coeff * content ** i) // fac_denom ** i
|
|
new_factors.append((fac_prim, i))
|
|
|
|
factors = new_factors
|
|
coeff = K0.convert(coeff, K1)
|
|
return coeff, factors
|
|
|
|
|
|
def dmp_qq_i_factor(f, u, K0):
|
|
"""Factor multivariate polynomials into irreducibles in `QQ_I[X]`. """
|
|
# Factor in QQ<I>
|
|
K1 = K0.as_AlgebraicField()
|
|
f = dmp_convert(f, u, K0, K1)
|
|
coeff, factors = dmp_factor_list(f, u, K1)
|
|
factors = [(dmp_convert(fac, u, K1, K0), i) for fac, i in factors]
|
|
coeff = K0.convert(coeff, K1)
|
|
return coeff, factors
|
|
|
|
|
|
def dmp_zz_i_factor(f, u, K0):
|
|
"""Factor multivariate polynomials into irreducibles in `ZZ_I[X]`. """
|
|
# First factor in QQ_I
|
|
K1 = K0.get_field()
|
|
f = dmp_convert(f, u, K0, K1)
|
|
coeff, factors = dmp_qq_i_factor(f, u, K1)
|
|
|
|
new_factors = []
|
|
for fac, i in factors:
|
|
# Extract content
|
|
fac_denom, fac_num = dmp_clear_denoms(fac, u, K1)
|
|
fac_num_ZZ_I = dmp_convert(fac_num, u, K1, K0)
|
|
content, fac_prim = dmp_ground_primitive(fac_num_ZZ_I, u, K1)
|
|
|
|
coeff = (coeff * content ** i) // fac_denom ** i
|
|
new_factors.append((fac_prim, i))
|
|
|
|
factors = new_factors
|
|
coeff = K0.convert(coeff, K1)
|
|
return coeff, factors
|
|
|
|
|
|
def dup_ext_factor(f, K):
|
|
"""Factor univariate polynomials over algebraic number fields. """
|
|
n, lc = dup_degree(f), dup_LC(f, K)
|
|
|
|
f = dup_monic(f, K)
|
|
|
|
if n <= 0:
|
|
return lc, []
|
|
if n == 1:
|
|
return lc, [(f, 1)]
|
|
|
|
f, F = dup_sqf_part(f, K), f
|
|
s, g, r = dup_sqf_norm(f, K)
|
|
|
|
factors = dup_factor_list_include(r, K.dom)
|
|
|
|
if len(factors) == 1:
|
|
return lc, [(f, n//dup_degree(f))]
|
|
|
|
H = s*K.unit
|
|
|
|
for i, (factor, _) in enumerate(factors):
|
|
h = dup_convert(factor, K.dom, K)
|
|
h, _, g = dup_inner_gcd(h, g, K)
|
|
h = dup_shift(h, H, K)
|
|
factors[i] = h
|
|
|
|
factors = dup_trial_division(F, factors, K)
|
|
return lc, factors
|
|
|
|
|
|
def dmp_ext_factor(f, u, K):
|
|
"""Factor multivariate polynomials over algebraic number fields. """
|
|
if not u:
|
|
return dup_ext_factor(f, K)
|
|
|
|
lc = dmp_ground_LC(f, u, K)
|
|
f = dmp_ground_monic(f, u, K)
|
|
|
|
if all(d <= 0 for d in dmp_degree_list(f, u)):
|
|
return lc, []
|
|
|
|
f, F = dmp_sqf_part(f, u, K), f
|
|
s, g, r = dmp_sqf_norm(f, u, K)
|
|
|
|
factors = dmp_factor_list_include(r, u, K.dom)
|
|
|
|
if len(factors) == 1:
|
|
factors = [f]
|
|
else:
|
|
H = dmp_raise([K.one, s*K.unit], u, 0, K)
|
|
|
|
for i, (factor, _) in enumerate(factors):
|
|
h = dmp_convert(factor, u, K.dom, K)
|
|
h, _, g = dmp_inner_gcd(h, g, u, K)
|
|
h = dmp_compose(h, H, u, K)
|
|
factors[i] = h
|
|
|
|
return lc, dmp_trial_division(F, factors, u, K)
|
|
|
|
|
|
def dup_gf_factor(f, K):
|
|
"""Factor univariate polynomials over finite fields. """
|
|
f = dup_convert(f, K, K.dom)
|
|
|
|
coeff, factors = gf_factor(f, K.mod, K.dom)
|
|
|
|
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_factor(f, u, K):
|
|
"""Factor multivariate polynomials over finite fields. """
|
|
raise NotImplementedError('multivariate polynomials over finite fields')
|
|
|
|
|
|
def dup_factor_list(f, K0):
|
|
"""Factor univariate polynomials into irreducibles in `K[x]`. """
|
|
j, f = dup_terms_gcd(f, K0)
|
|
cont, f = dup_primitive(f, K0)
|
|
|
|
if K0.is_FiniteField:
|
|
coeff, factors = dup_gf_factor(f, K0)
|
|
elif K0.is_Algebraic:
|
|
coeff, factors = dup_ext_factor(f, K0)
|
|
elif K0.is_GaussianRing:
|
|
coeff, factors = dup_zz_i_factor(f, K0)
|
|
elif K0.is_GaussianField:
|
|
coeff, factors = dup_qq_i_factor(f, K0)
|
|
else:
|
|
if not K0.is_Exact:
|
|
K0_inexact, K0 = K0, K0.get_exact()
|
|
f = dup_convert(f, K0_inexact, K0)
|
|
else:
|
|
K0_inexact = None
|
|
|
|
if K0.is_Field:
|
|
K = K0.get_ring()
|
|
|
|
denom, f = dup_clear_denoms(f, K0, K)
|
|
f = dup_convert(f, K0, K)
|
|
else:
|
|
K = K0
|
|
|
|
if K.is_ZZ:
|
|
coeff, factors = dup_zz_factor(f, K)
|
|
elif K.is_Poly:
|
|
f, u = dmp_inject(f, 0, K)
|
|
|
|
coeff, factors = dmp_factor_list(f, u, K.dom)
|
|
|
|
for i, (f, k) in enumerate(factors):
|
|
factors[i] = (dmp_eject(f, u, K), k)
|
|
|
|
coeff = K.convert(coeff, K.dom)
|
|
else: # pragma: no cover
|
|
raise DomainError('factorization not supported over %s' % K0)
|
|
|
|
if K0.is_Field:
|
|
for i, (f, k) in enumerate(factors):
|
|
factors[i] = (dup_convert(f, K, K0), k)
|
|
|
|
coeff = K0.convert(coeff, K)
|
|
coeff = K0.quo(coeff, denom)
|
|
|
|
if K0_inexact:
|
|
for i, (f, k) in enumerate(factors):
|
|
max_norm = dup_max_norm(f, K0)
|
|
f = dup_quo_ground(f, max_norm, K0)
|
|
f = dup_convert(f, K0, K0_inexact)
|
|
factors[i] = (f, k)
|
|
coeff = K0.mul(coeff, K0.pow(max_norm, k))
|
|
|
|
coeff = K0_inexact.convert(coeff, K0)
|
|
K0 = K0_inexact
|
|
|
|
if j:
|
|
factors.insert(0, ([K0.one, K0.zero], j))
|
|
|
|
return coeff*cont, _sort_factors(factors)
|
|
|
|
|
|
def dup_factor_list_include(f, K):
|
|
"""Factor univariate polynomials into irreducibles in `K[x]`. """
|
|
coeff, factors = dup_factor_list(f, K)
|
|
|
|
if not factors:
|
|
return [(dup_strip([coeff]), 1)]
|
|
else:
|
|
g = dup_mul_ground(factors[0][0], coeff, K)
|
|
return [(g, factors[0][1])] + factors[1:]
|
|
|
|
|
|
def dmp_factor_list(f, u, K0):
|
|
"""Factor multivariate polynomials into irreducibles in `K[X]`. """
|
|
if not u:
|
|
return dup_factor_list(f, K0)
|
|
|
|
J, f = dmp_terms_gcd(f, u, K0)
|
|
cont, f = dmp_ground_primitive(f, u, K0)
|
|
|
|
if K0.is_FiniteField: # pragma: no cover
|
|
coeff, factors = dmp_gf_factor(f, u, K0)
|
|
elif K0.is_Algebraic:
|
|
coeff, factors = dmp_ext_factor(f, u, K0)
|
|
elif K0.is_GaussianRing:
|
|
coeff, factors = dmp_zz_i_factor(f, u, K0)
|
|
elif K0.is_GaussianField:
|
|
coeff, factors = dmp_qq_i_factor(f, u, K0)
|
|
else:
|
|
if not K0.is_Exact:
|
|
K0_inexact, K0 = K0, K0.get_exact()
|
|
f = dmp_convert(f, u, K0_inexact, K0)
|
|
else:
|
|
K0_inexact = None
|
|
|
|
if K0.is_Field:
|
|
K = K0.get_ring()
|
|
|
|
denom, f = dmp_clear_denoms(f, u, K0, K)
|
|
f = dmp_convert(f, u, K0, K)
|
|
else:
|
|
K = K0
|
|
|
|
if K.is_ZZ:
|
|
levels, f, v = dmp_exclude(f, u, K)
|
|
coeff, factors = dmp_zz_factor(f, v, K)
|
|
|
|
for i, (f, k) in enumerate(factors):
|
|
factors[i] = (dmp_include(f, levels, v, K), k)
|
|
elif K.is_Poly:
|
|
f, v = dmp_inject(f, u, K)
|
|
|
|
coeff, factors = dmp_factor_list(f, v, K.dom)
|
|
|
|
for i, (f, k) in enumerate(factors):
|
|
factors[i] = (dmp_eject(f, v, K), k)
|
|
|
|
coeff = K.convert(coeff, K.dom)
|
|
else: # pragma: no cover
|
|
raise DomainError('factorization not supported over %s' % K0)
|
|
|
|
if K0.is_Field:
|
|
for i, (f, k) in enumerate(factors):
|
|
factors[i] = (dmp_convert(f, u, K, K0), k)
|
|
|
|
coeff = K0.convert(coeff, K)
|
|
coeff = K0.quo(coeff, denom)
|
|
|
|
if K0_inexact:
|
|
for i, (f, k) in enumerate(factors):
|
|
max_norm = dmp_max_norm(f, u, K0)
|
|
f = dmp_quo_ground(f, max_norm, u, K0)
|
|
f = dmp_convert(f, u, K0, K0_inexact)
|
|
factors[i] = (f, k)
|
|
coeff = K0.mul(coeff, K0.pow(max_norm, k))
|
|
|
|
coeff = K0_inexact.convert(coeff, K0)
|
|
K0 = K0_inexact
|
|
|
|
for i, j in enumerate(reversed(J)):
|
|
if not j:
|
|
continue
|
|
|
|
term = {(0,)*(u - i) + (1,) + (0,)*i: K0.one}
|
|
factors.insert(0, (dmp_from_dict(term, u, K0), j))
|
|
|
|
return coeff*cont, _sort_factors(factors)
|
|
|
|
|
|
def dmp_factor_list_include(f, u, K):
|
|
"""Factor multivariate polynomials into irreducibles in `K[X]`. """
|
|
if not u:
|
|
return dup_factor_list_include(f, K)
|
|
|
|
coeff, factors = dmp_factor_list(f, u, K)
|
|
|
|
if not factors:
|
|
return [(dmp_ground(coeff, u), 1)]
|
|
else:
|
|
g = dmp_mul_ground(factors[0][0], coeff, u, K)
|
|
return [(g, factors[0][1])] + factors[1:]
|
|
|
|
|
|
def dup_irreducible_p(f, K):
|
|
"""
|
|
Returns ``True`` if a univariate polynomial ``f`` has no factors
|
|
over its domain.
|
|
"""
|
|
return dmp_irreducible_p(f, 0, K)
|
|
|
|
|
|
def dmp_irreducible_p(f, u, K):
|
|
"""
|
|
Returns ``True`` if a multivariate polynomial ``f`` has no factors
|
|
over its domain.
|
|
"""
|
|
_, factors = dmp_factor_list(f, u, K)
|
|
|
|
if not factors:
|
|
return True
|
|
elif len(factors) > 1:
|
|
return False
|
|
else:
|
|
_, k = factors[0]
|
|
return k == 1
|