98 lines
3.2 KiB
C
98 lines
3.2 KiB
C
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/*=============================================================================
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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) 2008, 2009 William Hart
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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_vec.h"
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#include "fmpz_poly.h"
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/*
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Assumes poly1 and poly2 are not length 0 and 0 < n <= len1 + len2 - 1.
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*/
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void
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_fmpz_poly_mullow_classical(fmpz * res, const fmpz * poly1, slong len1,
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const fmpz * poly2, slong len2, slong n)
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{
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if ((len1 == 1 && len2 == 1) || n == 1) /* Special case if the length of output is 1 */
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{
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fmpz_mul(res, poly1, poly2);
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}
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else /* Ordinary case */
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{
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slong i;
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/* Set res[i] = poly1[i]*poly2[0] */
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_fmpz_vec_scalar_mul_fmpz(res, poly1, FLINT_MIN(len1, n), poly2);
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/* Set res[i+len1-1] = in1[len1-1]*in2[i] */
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if (n > len1)
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_fmpz_vec_scalar_mul_fmpz(res + len1, poly2 + 1, n - len1,
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poly1 + len1 - 1);
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/* out[i+j] += in1[i]*in2[j] */
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for (i = 0; i < FLINT_MIN(len1, n) - 1; i++)
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_fmpz_vec_scalar_addmul_fmpz(res + i + 1, poly2 + 1,
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FLINT_MIN(len2, n - i) - 1,
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poly1 + i);
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}
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}
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void
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fmpz_poly_mullow_classical(fmpz_poly_t res, const fmpz_poly_t poly1,
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const fmpz_poly_t poly2, slong n)
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{
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slong len_out;
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if (poly1->length == 0 || poly2->length == 0 || n == 0)
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{
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fmpz_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 (n > len_out)
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n = len_out;
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if (res == poly1 || res == poly2)
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{
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fmpz_poly_t t;
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fmpz_poly_init2(t, n);
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_fmpz_poly_mullow_classical(t->coeffs, poly1->coeffs, poly1->length,
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poly2->coeffs, poly2->length, n);
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fmpz_poly_swap(res, t);
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fmpz_poly_clear(t);
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}
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else
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{
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fmpz_poly_fit_length(res, n);
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_fmpz_poly_mullow_classical(res->coeffs, poly1->coeffs, poly1->length,
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poly2->coeffs, poly2->length, n);
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}
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_fmpz_poly_set_length(res, n);
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_fmpz_poly_normalise(res);
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}
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