121 lines
4.7 KiB
C
121 lines
4.7 KiB
C
/*=============================================================================
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This file is part of FLINT.
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FLINT is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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FLINT is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with FLINT; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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=============================================================================*/
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/******************************************************************************
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Copyright (C) 2011 Andy Novocin
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Copyright (C) 2011 Sebastian Pancratz
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******************************************************************************/
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#include <gmp.h>
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#include "flint.h"
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#include "fmpz.h"
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#include "fmpz_poly.h"
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#include "fmpz_mod_poly.h"
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/*
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Macro for the lift B := [{(1 - aG - bH)/p} * b mod g] p + b,
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of length at most lenG - 1.
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Assumes that {C, lenC} contains the inner part {(1 - aG - bH)/p} mod p1,
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where lenC = max(lenA + lenG - 1, lenB + lenH - 1). Requires temporary
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space M, D, E. We really only need
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lenM = max(lenG, lenH)
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lenE = max(lenG + lenB - 2, lenH + lenA - 2)
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lenD = max(lenC, lenE)
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Writes {B, lenG - 1}. The cofactor that is lifted is the
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polynomial {b, lenB}, which may be aliased with B. Although
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it suffices to have g modulo p, there is no harm in supplying
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{g, lenG} only reduced modulo p p1.
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*/
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#define liftinv(B, b, lenB, g, lenG) \
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do { \
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_fmpz_vec_scalar_mod_fmpz(M, g, lenG, p1); \
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_fmpz_mod_poly_rem(D, C, lenC, M, lenG, one, p1); \
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_fmpz_mod_poly_mul(E, D, lenG - 1, b, lenB, p1); \
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if (lenB > 1) \
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{ \
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_fmpz_mod_poly_rem(D, E, lenG + lenB - 2, M, lenG, one, p1); \
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_fmpz_vec_scalar_mul_fmpz(M, D, lenG - 1, p); \
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} \
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else \
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{ \
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_fmpz_vec_scalar_mul_fmpz(M, E, lenG - 1, p); \
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} \
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_fmpz_poly_add(B, M, lenG - 1, b, lenB); \
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} while (0)
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void _fmpz_poly_hensel_lift_only_inverse(fmpz *A, fmpz *B,
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const fmpz *G, slong lenG, const fmpz *H, slong lenH,
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const fmpz *a, slong lenA, const fmpz *b, slong lenB,
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const fmpz_t p, const fmpz_t p1)
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{
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const fmpz one[1] = {WORD(1)};
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const slong lenC = FLINT_MAX(lenA + lenG - 1, lenB + lenH - 1);
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const slong lenM = FLINT_MAX(lenG, lenH);
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const slong lenE = FLINT_MAX(lenG + lenB - 2, lenH + lenA - 2);
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const slong lenD = FLINT_MAX(lenC, lenE);
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fmpz *C, *D, *E, *M;
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C = _fmpz_vec_init(lenC + lenD + lenD + lenM);
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D = C + lenC;
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E = D + lenD;
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M = E + lenE;
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if (lenG >= lenA)
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_fmpz_poly_mul(C, G, lenG, a, lenA);
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else
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_fmpz_poly_mul(C, a, lenA, G, lenG);
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if (lenH >= lenB)
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_fmpz_poly_mul(D, H, lenH, b, lenB);
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else
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_fmpz_poly_mul(D, b, lenB, H, lenH);
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_fmpz_vec_add(C, C, D, lenC);
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fmpz_sub_ui(C, C, 1);
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_fmpz_vec_neg(C, C, lenC);
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_fmpz_vec_scalar_divexact_fmpz(D, C, lenC, p);
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_fmpz_vec_scalar_mod_fmpz(C, D, lenC, p1);
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liftinv(B, b, lenB, G, lenG);
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liftinv(A, a, lenA, H, lenH);
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_fmpz_vec_clear(C, lenC + lenD + lenD + lenM);
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}
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void fmpz_poly_hensel_lift_only_inverse(fmpz_poly_t Aout, fmpz_poly_t Bout,
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const fmpz_poly_t G, const fmpz_poly_t H,
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const fmpz_poly_t a, const fmpz_poly_t b,
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const fmpz_t p, const fmpz_t p1)
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{
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fmpz_poly_fit_length(Aout, H->length - 1);
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fmpz_poly_fit_length(Bout, G->length - 1);
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_fmpz_poly_hensel_lift_only_inverse(Aout->coeffs, Bout->coeffs,
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G->coeffs, G->length, H->coeffs, H->length,
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a->coeffs, a->length, b->coeffs, b->length, p, p1);
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_fmpz_poly_set_length(Aout, H->length - 1);
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_fmpz_poly_set_length(Bout, G->length - 1);
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_fmpz_poly_normalise(Aout);
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_fmpz_poly_normalise(Bout);
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}
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