95 lines
3.1 KiB
C
95 lines
3.1 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 <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 and len1 >= len2. */
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void
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_fmpz_poly_mulmid_classical(fmpz * res, const fmpz * poly1,
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slong len1, const fmpz * poly2, slong len2)
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{
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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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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 + len2 - 1, len1 - len2 + 1,
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poly2);
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/* out[i+j] += in1[i]*in2[j] */
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for (i = 0; i < len2 - 1; i++)
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_fmpz_vec_scalar_addmul_fmpz(res, poly2 + len2 - i - 1,
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FLINT_MIN(i + 1, len1 - len2 + 1),
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poly1 + i);
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for (; i < len1 - 1; i++)
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_fmpz_vec_scalar_addmul_fmpz(res + i - len2 + 2, poly2 + 1,
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FLINT_MIN(len2 - 1, len1 - 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_mulmid_classical(fmpz_poly_t res,
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const fmpz_poly_t poly1, const fmpz_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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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 (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_mulmid_classical(temp->coeffs, poly1->coeffs, poly1->length,
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poly2->coeffs, poly2->length);
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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_mulmid_classical(res->coeffs, poly1->coeffs, poly1->length,
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poly2->coeffs, poly2->length);
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}
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_fmpz_poly_set_length(res, len_out);
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_fmpz_poly_normalise(res);
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}
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