102 lines
3.4 KiB
C
102 lines
3.4 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) 2010 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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/* Assumes poly1 and poly2 are not length 0. */
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void
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_fmpz_poly_mulhigh_classical(fmpz * res, const fmpz * poly1,
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slong len1, const fmpz * poly2, slong len2,
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slong start)
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{
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_fmpz_vec_zero(res, start);
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if (len1 == 1 && len2 == 1) /* Special case if the length of both inputs is 1 */
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{
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if (start == 0)
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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, m, n;
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/* Set res[i] = poly1[i]*poly2[0] */
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if (start < len1)
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_fmpz_vec_scalar_mul_fmpz(res + start, poly1 + start, len1 - start,
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poly2);
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/* Set res[i+len1-1] = in1[len1-1]*in2[i] */
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m = FLINT_MAX(len1 - 1, start);
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_fmpz_vec_scalar_mul_fmpz(res + m, poly2 + m - len1 + 1,
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len2 - 1 + len1 - m, poly1 + len1 - 1);
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/* out[i+j] += in1[i]*in2[j] */
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m = FLINT_MAX(start, len2 - 1);
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for (i = m - len2 + 1; i < len1 - 1; i++)
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{
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n = FLINT_MAX(i + 1, start);
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_fmpz_vec_scalar_addmul_fmpz(res + n, poly2 + n - i, len2 + i - n,
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poly1 + i);
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}
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}
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}
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void
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fmpz_poly_mulhigh_classical(fmpz_poly_t res,
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const fmpz_poly_t poly1, const fmpz_poly_t poly2,
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slong start)
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{
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slong len_out = poly1->length + poly2->length - 1;
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if (poly1->length == 0 || poly2->length == 0 || start >= len_out)
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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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if (res == poly1 || res == poly2)
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{
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fmpz_poly_t temp;
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fmpz_poly_init2(temp, len_out);
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_fmpz_poly_mulhigh_classical(temp->coeffs, poly1->coeffs,
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poly1->length, poly2->coeffs,
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poly2->length, start);
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fmpz_poly_swap(res, temp);
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fmpz_poly_clear(temp);
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}
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else
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{
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fmpz_poly_fit_length(res, len_out);
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_fmpz_poly_mulhigh_classical(res->coeffs, poly1->coeffs, poly1->length,
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poly2->coeffs, poly2->length, start);
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}
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_fmpz_poly_set_length(res, len_out);
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}
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