111 lines
3.1 KiB
C
111 lines
3.1 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) 2011 Fredrik Johansson
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Copyright (C) 2012 Lina Kulakova
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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 "fmpz_vec.h"
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#include "fmpz_mod_poly.h"
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void _fmpz_mod_poly_mulmod(fmpz * res, const fmpz * poly1, slong len1,
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const fmpz * poly2, slong len2, const fmpz * f,
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slong lenf, const fmpz_t p)
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{
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fmpz * T, * Q;
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fmpz_t invf;
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slong lenT, lenQ;
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lenT = len1 + len2 - 1;
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lenQ = lenT - lenf + 1;
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T = _fmpz_vec_init(lenT + lenQ);
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Q = T + lenT;
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if (len1 >= len2)
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_fmpz_mod_poly_mul(T, poly1, len1, poly2, len2, p);
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else
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_fmpz_mod_poly_mul(T, poly2, len2, poly1, len1, p);
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fmpz_init(invf);
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fmpz_invmod(invf, f + lenf - 1, p);
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_fmpz_mod_poly_divrem(Q, res, T, lenT, f, lenf, invf, p);
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_fmpz_vec_clear(T, lenT + lenQ);
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fmpz_clear(invf);
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}
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void
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fmpz_mod_poly_mulmod(fmpz_mod_poly_t res, const fmpz_mod_poly_t poly1,
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const fmpz_mod_poly_t poly2, const fmpz_mod_poly_t f)
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{
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slong len1, len2, lenf;
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fmpz * fcoeffs;
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lenf = f->length;
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len1 = poly1->length;
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len2 = poly2->length;
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if (lenf == 0)
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{
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flint_printf("Exception (fmpz_mod_poly_mulmod). Divide by zero\n");
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abort();
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}
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if (lenf == 1 || len1 == 0 || len2 == 0)
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{
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fmpz_mod_poly_zero(res);
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return;
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}
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if (len1 + len2 - lenf > 0)
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{
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if (f == res)
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{
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fcoeffs = _fmpz_vec_init(lenf);
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_fmpz_vec_set(fcoeffs, f->coeffs, lenf);
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}
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else
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fcoeffs = f->coeffs;
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fmpz_mod_poly_fit_length(res, len1 + len2 - 1);
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_fmpz_mod_poly_mulmod(res->coeffs, poly1->coeffs, len1,
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poly2->coeffs, len2,
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fcoeffs, lenf,
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&res->p);
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if (f == res)
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_fmpz_vec_clear(fcoeffs, lenf);
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_fmpz_mod_poly_set_length(res, lenf - 1);
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_fmpz_mod_poly_normalise(res);
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}
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else
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{
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fmpz_mod_poly_mul(res, poly1, poly2);
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}
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}
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