109 lines
3.2 KiB
C
109 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) 2011 Fredrik Johansson
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Copyright (C) 2012 Lina Kulakova
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******************************************************************************/
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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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#include "ulong_extras.h"
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void
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_fmpz_mod_poly_compose_mod(fmpz * res, const fmpz * f, slong lenf, const fmpz * g,
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const fmpz * h, slong lenh, const fmpz_t p)
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{
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if (lenh < 12 || lenf >= lenh)
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_fmpz_mod_poly_compose_mod_horner(res, f, lenf, g, h, lenh, p);
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else
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_fmpz_mod_poly_compose_mod_brent_kung(res, f, lenf, g, h, lenh, p);
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}
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void
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fmpz_mod_poly_compose_mod(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 poly3)
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{
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fmpz_t inv3;
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slong len1 = poly1->length;
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slong len2 = poly2->length;
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slong len3 = poly3->length;
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slong len = len3 - 1;
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slong vec_len = FLINT_MAX(len3 - 1, len2);
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fmpz * ptr2;
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if (len3 == 0)
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{
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flint_printf("Exception (fmpz_mod_poly_compose_mod)."
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"Division by zero.\n");
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abort();
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}
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if (len1 == 0 || len3 == 1)
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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 == 1)
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{
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fmpz_mod_poly_set(res, poly1);
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return;
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}
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if (res == poly3 || res == poly1)
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{
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fmpz_mod_poly_t tmp;
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fmpz_mod_poly_init(tmp, &res->p);
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fmpz_mod_poly_compose_mod(tmp, poly1, poly2, poly3);
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fmpz_mod_poly_swap(tmp, res);
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fmpz_mod_poly_clear(tmp);
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return;
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}
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ptr2 = _fmpz_vec_init(vec_len);
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if (len2 <= len)
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{
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_fmpz_vec_set(ptr2, poly2->coeffs, len2);
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_fmpz_vec_zero(ptr2 + len2, len - len2);
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}
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else
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{
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fmpz_init(inv3);
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fmpz_invmod(inv3, poly3->coeffs + len, &res->p);
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_fmpz_mod_poly_rem(ptr2, poly2->coeffs, len2,
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poly3->coeffs, len3, inv3, &res->p);
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fmpz_clear(inv3);
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}
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fmpz_mod_poly_fit_length(res, len);
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_fmpz_mod_poly_compose_mod(res->coeffs,
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poly1->coeffs, len1, ptr2, poly3->coeffs, len3, &res->p);
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_fmpz_mod_poly_set_length(res, len);
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_fmpz_mod_poly_normalise(res);
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_fmpz_vec_clear(ptr2, vec_len);
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}
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