pqc/external/flint-2.4.3/fmpz_poly/hensel_lift_without_inverse.c
2014-05-24 23:16:06 +02:00

109 lines
4.2 KiB
C

/*=============================================================================
This file is part of FLINT.
FLINT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
FLINT is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with FLINT; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2011 Andy Novocin
Copyright (C) 2011 Sebastian Pancratz
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "fmpz.h"
#include "fmpz_poly.h"
#include "fmpz_mod_poly.h"
/*
Macro for the lift G := [{(f - gh)/p} * b mod g] p + g.
Assumes that {C, lenF} contains the inner part {f - gh}/p mod p1.
Requires temporary space M, D, E. We really only need
lenM = max(lenG, lenH)
lenE = max(lenG + lenB - 2, lenH + lenA - 2)
lenD = max(lenE, lenF)
Only supports aliasing between G and g.
*/
#define lift(G, g, lenG, b, lenB) \
do { \
_fmpz_vec_scalar_mod_fmpz(M, g, lenG, p1); \
_fmpz_mod_poly_rem(D, C, lenF, M, lenG, one, p1); \
_fmpz_mod_poly_mul(E, D, lenG - 1, b, lenB, p1); \
if (lenB > 1) \
{ \
_fmpz_mod_poly_rem(D, E, lenG + lenB - 2, M, lenG, one, p1); \
_fmpz_vec_scalar_mul_fmpz(M, D, lenG - 1, p); \
} \
else \
{ \
_fmpz_vec_scalar_mul_fmpz(M, E, lenG - 1, p); \
} \
_fmpz_vec_add(G, g, M, lenG - 1); \
fmpz_one(G + lenG - 1); \
} while (0)
void _fmpz_poly_hensel_lift_without_inverse(fmpz *G, fmpz *H,
const fmpz *f, slong lenF,
const fmpz *g, slong lenG, const fmpz *h, slong lenH,
const fmpz *a, slong lenA, const fmpz *b, slong lenB,
const fmpz_t p, const fmpz_t p1)
{
const fmpz one[1] = {1l};
const slong lenM = FLINT_MAX(lenG, lenH);
const slong lenE = FLINT_MAX(lenG + lenB - 2, lenH + lenA - 2);
const slong lenD = FLINT_MAX(lenE, lenF);
fmpz *C, *D, *E, *M;
C = _fmpz_vec_init(lenF + lenD + lenE + lenM);
D = C + lenF;
E = D + lenD;
M = E + lenE;
if (lenG >= lenH)
_fmpz_poly_mul(C, g,lenG, h, lenH);
else
_fmpz_poly_mul(C, h, lenH, g, lenG);
_fmpz_vec_sub(C, f, C, lenF);
_fmpz_vec_scalar_divexact_fmpz(D, C, lenF, p);
_fmpz_vec_scalar_mod_fmpz(C, D, lenF, p1);
lift(G, g, lenG, b, lenB);
lift(H, h, lenH, a, lenA);
_fmpz_vec_clear(C, lenF + lenD + lenE + lenM);
}
void fmpz_poly_hensel_lift_without_inverse(fmpz_poly_t Gout, fmpz_poly_t Hout,
const fmpz_poly_t f, const fmpz_poly_t g, const fmpz_poly_t h,
const fmpz_poly_t a, const fmpz_poly_t b,
const fmpz_t p, const fmpz_t p1)
{
fmpz_poly_fit_length(Gout, g->length);
fmpz_poly_fit_length(Hout, h->length);
_fmpz_poly_set_length(Gout, g->length);
_fmpz_poly_set_length(Hout, h->length);
_fmpz_poly_hensel_lift_without_inverse(Gout->coeffs, Hout->coeffs,
f->coeffs, f->length, g->coeffs, g->length, h->coeffs, h->length,
a->coeffs, a->length, b->coeffs, b->length, p, p1);
}