120 lines
4.0 KiB
C
120 lines
4.0 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) 2010 William Hart
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******************************************************************************/
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#include <stdlib.h>
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#include <gmp.h>
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#include "flint.h"
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#include "nmod_vec.h"
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#include "nmod_poly.h"
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/* Assumes poly1 and poly2 are not length 0. */
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void
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_nmod_poly_mul_classical(mp_ptr res, mp_srcptr poly1,
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slong len1, mp_srcptr poly2, slong len2, nmod_t mod)
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{
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slong i;
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slong log_len = FLINT_BIT_COUNT(len2);
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slong bits = FLINT_BITS - (slong) mod.norm;
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if (2 * bits + log_len <= FLINT_BITS)
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{
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/* Set res[i] = poly1[i]*poly2[0] */
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mpn_mul_1(res, poly1, len1, poly2[0]);
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if (len2 != 1)
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{
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/* Set res[i+len1-1] = in1[len1-1]*in2[i] */
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mpn_mul_1(res + len1, poly2 + 1, len2 - 1, poly1[len1 - 1]);
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/* out[i+j] += in1[i]*in2[j] */
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for (i = 0; i < len1 - 1; i++)
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mpn_addmul_1(res + i + 1, poly2 + 1, len2 - 1, poly1[i]);
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}
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/* final reduction */
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_nmod_vec_reduce(res, res, len1 + len2 - 1, mod);
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}
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else
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{
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/* Set res[i] = poly1[i]*poly2[0] */
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_nmod_vec_scalar_mul_nmod(res, poly1, len1, poly2[0], mod);
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if (len2 == 1)
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return;
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/* Set res[i+len1-1] = in1[len1-1]*in2[i] */
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_nmod_vec_scalar_mul_nmod(res + len1, poly2 + 1, len2 - 1,
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poly1[len1 - 1], mod);
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/* out[i+j] += in1[i]*in2[j] */
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for (i = 0; i < len1 - 1; i++)
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_nmod_vec_scalar_addmul_nmod(res + i + 1, poly2 + 1, len2 - 1,
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poly1[i], mod);
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}
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}
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void
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nmod_poly_mul_classical(nmod_poly_t res,
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const nmod_poly_t poly1, const nmod_poly_t poly2)
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{
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slong len_out;
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if ((poly1->length == 0) || (poly2->length == 0))
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{
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nmod_poly_zero(res);
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return;
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}
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len_out = poly1->length + poly2->length - 1;
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if (res == poly1 || res == poly2)
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{
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nmod_poly_t temp;
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nmod_poly_init2_preinv(temp, poly1->mod.n, poly1->mod.ninv, len_out);
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if (poly1->length >= poly2->length)
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_nmod_poly_mul_classical(temp->coeffs, poly1->coeffs,
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poly1->length, poly2->coeffs,
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poly2->length, poly1->mod);
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else
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_nmod_poly_mul_classical(temp->coeffs, poly2->coeffs,
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poly2->length, poly1->coeffs,
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poly1->length, poly1->mod);
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nmod_poly_swap(res, temp);
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nmod_poly_clear(temp);
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}
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else
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{
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nmod_poly_fit_length(res, len_out);
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if (poly1->length >= poly2->length)
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_nmod_poly_mul_classical(res->coeffs, poly1->coeffs, poly1->length,
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poly2->coeffs, poly2->length, poly1->mod);
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else
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_nmod_poly_mul_classical(res->coeffs, poly2->coeffs, poly2->length,
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poly1->coeffs, poly1->length, poly1->mod);
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}
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res->length = len_out;
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_nmod_poly_normalise(res);
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}
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