99 lines
2.8 KiB
C
99 lines
2.8 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 Sebastian Pancratz
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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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void
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_fmpz_poly_gcd(fmpz * res, const fmpz * poly1, slong len1,
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const fmpz * poly2, slong len2)
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{
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if (len1 < 6)
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{
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_fmpz_poly_gcd_subresultant(res, poly1, len1, poly2, len2);
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}
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else
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{
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slong b1, b2;
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b1 = _fmpz_vec_max_bits(poly1, len1);
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b2 = _fmpz_vec_max_bits(poly2, len2);
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b1 = FLINT_ABS(b1);
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b2 = FLINT_ABS(b2);
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if (b1 + b2 < 2 * FLINT_BITS)
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{
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if (_fmpz_poly_gcd_heuristic(res, poly1, len1, poly2, len2))
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return;
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}
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_fmpz_poly_gcd_modular(res, poly1, len1, poly2, len2);
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}
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}
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void
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fmpz_poly_gcd(fmpz_poly_t res, const fmpz_poly_t poly1,
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const fmpz_poly_t poly2)
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{
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if (poly1->length < poly2->length)
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{
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fmpz_poly_gcd(res, poly2, poly1);
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}
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else /* len1 >= len2 >= 0 */
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{
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const slong len1 = poly1->length;
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const slong len2 = poly2->length;
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if (len1 == 0) /* len1 = len2 = 0 */
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{
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fmpz_poly_zero(res);
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}
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else if (len2 == 0) /* len1 > len2 = 0 */
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{
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if (fmpz_sgn(poly1->coeffs + (len1 - 1)) > 0)
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fmpz_poly_set(res, poly1);
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else
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fmpz_poly_neg(res, poly1);
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}
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else /* len1 >= len2 >= 1 */
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{
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/* all current gcd functions automatically handle aliasing */
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fmpz_poly_fit_length(res, len2);
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_fmpz_poly_gcd(res->coeffs, poly1->coeffs, len1,
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poly2->coeffs, len2);
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_fmpz_poly_set_length(res, len2);
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_fmpz_poly_normalise(res);
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}
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}
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}
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