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/*=============================================================================
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) 2010 William Hart
******************************************************************************/
#include <stdlib.h>
#include <gmp.h>
#include "flint.h"
#include "nmod_vec.h"
#include "nmod_poly.h"
/* Assumes poly1 and poly2 are not length 0. */
void
_nmod_poly_mul_classical(mp_ptr res, mp_srcptr poly1,
slong len1, mp_srcptr poly2, slong len2, nmod_t mod)
{
slong i;
slong log_len = FLINT_BIT_COUNT(len2);
slong bits = FLINT_BITS - (slong) mod.norm;
if (2 * bits + log_len <= FLINT_BITS)
{
/* Set res[i] = poly1[i]*poly2[0] */
mpn_mul_1(res, poly1, len1, poly2[0]);
if (len2 != 1)
{
/* Set res[i+len1-1] = in1[len1-1]*in2[i] */
mpn_mul_1(res + len1, poly2 + 1, len2 - 1, poly1[len1 - 1]);
/* out[i+j] += in1[i]*in2[j] */
for (i = 0; i < len1 - 1; i++)
mpn_addmul_1(res + i + 1, poly2 + 1, len2 - 1, poly1[i]);
}
/* final reduction */
_nmod_vec_reduce(res, res, len1 + len2 - 1, mod);
}
else
{
/* Set res[i] = poly1[i]*poly2[0] */
_nmod_vec_scalar_mul_nmod(res, poly1, len1, poly2[0], mod);
if (len2 == 1)
return;
/* Set res[i+len1-1] = in1[len1-1]*in2[i] */
_nmod_vec_scalar_mul_nmod(res + len1, poly2 + 1, len2 - 1,
poly1[len1 - 1], mod);
/* out[i+j] += in1[i]*in2[j] */
for (i = 0; i < len1 - 1; i++)
_nmod_vec_scalar_addmul_nmod(res + i + 1, poly2 + 1, len2 - 1,
poly1[i], mod);
}
}
void
nmod_poly_mul_classical(nmod_poly_t res,
const nmod_poly_t poly1, const nmod_poly_t poly2)
{
slong len_out;
if ((poly1->length == 0) || (poly2->length == 0))
{
nmod_poly_zero(res);
return;
}
len_out = poly1->length + poly2->length - 1;
if (res == poly1 || res == poly2)
{
nmod_poly_t temp;
nmod_poly_init2_preinv(temp, poly1->mod.n, poly1->mod.ninv, len_out);
if (poly1->length >= poly2->length)
_nmod_poly_mul_classical(temp->coeffs, poly1->coeffs,
poly1->length, poly2->coeffs,
poly2->length, poly1->mod);
else
_nmod_poly_mul_classical(temp->coeffs, poly2->coeffs,
poly2->length, poly1->coeffs,
poly1->length, poly1->mod);
nmod_poly_swap(res, temp);
nmod_poly_clear(temp);
}
else
{
nmod_poly_fit_length(res, len_out);
if (poly1->length >= poly2->length)
_nmod_poly_mul_classical(res->coeffs, poly1->coeffs, poly1->length,
poly2->coeffs, poly2->length, poly1->mod);
else
_nmod_poly_mul_classical(res->coeffs, poly2->coeffs, poly2->length,
poly1->coeffs, poly1->length, poly1->mod);
}
res->length = len_out;
_nmod_poly_normalise(res);
}
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