pqc/external/flint-2.4.3/fmpz_poly/powers_precompute.c

78 lines
2.4 KiB
C
Raw Normal View History

2014-05-18 22:03:37 +00:00
/*=============================================================================
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) 2013 William Hart
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "fmpz.h"
#include "fmpz_poly.h"
fmpz **
_fmpz_poly_powers_precompute(const fmpz * B, slong len)
{
slong i;
fmpz ** powers = flint_malloc(sizeof(fmpz *)*(2*len - 1));
fmpz_poly_t pow, p;
fmpz_poly_init2(pow, len);
fmpz_poly_one(pow);
fmpz_poly_init2(p, len - 1);
for (i = 0; i < 2*len - 1; i++)
{
powers[i] = _fmpz_vec_init(len - 1);
if (pow->length == len) /* reduce pow mod B */
{
_fmpz_vec_scalar_mul_fmpz(p->coeffs, B, len - 1, pow->coeffs + pow->length - 1);
_fmpz_poly_set_length(p, len - 1);
_fmpz_poly_normalise(p);
fmpz_poly_sub(pow, pow, p);
_fmpz_poly_set_length(pow, len - 1);
_fmpz_poly_normalise(pow);
}
_fmpz_vec_set(powers[i], pow->coeffs, len - 1);
fmpz_poly_shift_left(pow, pow, 1);
}
fmpz_poly_clear(pow);
fmpz_poly_clear(p);
return powers;
}
void fmpz_poly_powers_precompute(fmpz_poly_powers_precomp_t pinv,
fmpz_poly_t poly)
{
if (poly->length == 0)
{
flint_printf("Exception (fmpz_poly_powers_precompute). Division by zero.\n");
abort();
}
pinv->powers = _fmpz_poly_powers_precompute(poly->coeffs, poly->length);
pinv->len = poly->length;
}