106 lines
3.1 KiB
C
106 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) 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_compose_horner(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 == 1)
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{
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fmpz_set(res, poly1);
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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;
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fmpz * t = _fmpz_vec_init(alloc);
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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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{
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lenr = len2;
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_fmpz_vec_scalar_mul_fmpz(res, poly2, len2, poly1 + i);
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i--;
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fmpz_add(res, res, poly1 + i);
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}
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while (i--)
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{
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_fmpz_poly_mul(t, res, lenr, poly2, len2);
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lenr += len2 - 1;
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_fmpz_poly_add(res, t, lenr, poly1 + i, 1);
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}
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_fmpz_vec_clear(t, alloc);
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}
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}
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void
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fmpz_poly_compose_horner(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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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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fmpz_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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fmpz_poly_set_fmpz(res, poly1->coeffs);
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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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fmpz_poly_fit_length(res, lenr);
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_fmpz_poly_compose_horner(res->coeffs, poly1->coeffs, len1,
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poly2->coeffs, len2);
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_fmpz_poly_set_length(res, lenr);
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}
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else
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{
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fmpz_poly_t t;
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fmpz_poly_init2(t, lenr);
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_fmpz_poly_compose_horner(t->coeffs, poly1->coeffs, len1,
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poly2->coeffs, len2);
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_fmpz_poly_set_length(t, lenr);
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fmpz_poly_swap(res, t);
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fmpz_poly_clear(t);
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}
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_fmpz_poly_normalise(res);
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}
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}
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