123 lines
3.6 KiB
C
123 lines
3.6 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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Copyright (C) 2012 Sebastian Pancratz
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******************************************************************************/
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#include "nmod_poly.h"
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#include "ulong_extras.h"
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void
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_nmod_poly_compose_horner(mp_ptr res, mp_srcptr poly1, slong len1,
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mp_srcptr poly2, slong len2, nmod_t mod)
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{
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if (len1 == 1)
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{
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res[0] = poly1[0];
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}
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else if (len2 == 1)
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{
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res[0] = _nmod_poly_evaluate_nmod(poly1, len1, poly2[0], mod);
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}
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else if (len1 == 2)
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{
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_nmod_vec_scalar_mul_nmod(res, poly2, len2, poly1[1], mod);
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res[0] = n_addmod(res[0], poly1[0], mod.n);
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}
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else
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{
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const slong alloc = (len1 - 1) * (len2 - 1) + 1;
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slong i = len1 - 1, lenr = len2;
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mp_limb_t *t, *t1, *t2;
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t = _nmod_vec_init(alloc);
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if (len1 % 2 == 0)
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{
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t1 = res;
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t2 = t;
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}
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else
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{
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t1 = t;
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t2 = res;
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}
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/* Perform the first two steps as one,
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"res = a(m) * poly2 + a(m-1)". */
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{
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_nmod_vec_scalar_mul_nmod(t1, poly2, len2, poly1[i], mod);
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i--;
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t1[0] = n_addmod(t1[0], poly1[i], mod.n);
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}
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while (i--)
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{
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_nmod_poly_mul(t2, t1, lenr, poly2, len2, mod);
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lenr += len2 - 1;
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MP_PTR_SWAP(t1, t2);
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t1[0] = n_addmod(t1[0], poly1[i], mod.n);
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}
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_nmod_vec_clear(t);
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}
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}
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void nmod_poly_compose_horner(nmod_poly_t res,
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const nmod_poly_t poly1, const nmod_poly_t poly2)
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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)
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{
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nmod_poly_zero(res);
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}
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else if (len1 == 1 || len2 == 0)
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{
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nmod_poly_fit_length(res, 1);
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res->coeffs[0] = poly1->coeffs[0];
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res->length = (res->coeffs[0] != 0);
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}
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else
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{
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const slong lenr = (len1 - 1) * (len2 - 1) + 1;
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if (res != poly1 && res != poly2)
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{
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nmod_poly_fit_length(res, lenr);
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_nmod_poly_compose_horner(res->coeffs, poly1->coeffs, len1,
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poly2->coeffs, len2, poly1->mod);
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}
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else
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{
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nmod_poly_t t;
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nmod_poly_init2(t, poly1->mod.n, lenr);
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_nmod_poly_compose_horner(t->coeffs, poly1->coeffs, len1,
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poly2->coeffs, len2, poly1->mod);
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nmod_poly_swap(res, t);
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nmod_poly_clear(t);
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}
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res->length = lenr;
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_nmod_poly_normalise(res);
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}
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}
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