109 lines
2.9 KiB
C
109 lines
2.9 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 "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_evaluate_divconquer_fmpz(fmpz_t res, const fmpz * poly, slong len,
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const fmpz_t x)
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{
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slong c, h, i, k = 1;
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fmpz *y, *T, *t = res, *u;
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h = FLINT_BIT_COUNT(len - 1); /* 2^{h-1} < len <= 2^h */
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y = _fmpz_vec_init(2 * h + 2); /* x^{2^0}, x^{2^1}, ..., x^{2^{h-1}} */
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T = y + h;
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u = y + 2 * h + 1;
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*y = *x;
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for (i = 1; i < h; i++)
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fmpz_mul(y + i, y + (i - 1), y + (i - 1));
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for (i = 0; i < len - 1; )
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{
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fmpz_mul(u, y + 0, poly + i + 1);
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fmpz_add(t, poly + i, u);
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i += 2;
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count_trailing_zeros(c, i);
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for (k = 1; k < c; k++)
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{
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fmpz_mul(u, y + k, t);
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fmpz_add(t, T + k, u);
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}
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fmpz_swap(T + k, t);
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}
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if (len & WORD(1))
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{
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fmpz_set(t, poly + (len - 1));
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count_trailing_zeros(c, len + 1);
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for (k = 1; k < c; k++)
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{
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fmpz_mul(u, y + k, t);
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fmpz_add(t, T + k, u);
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}
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fmpz_swap(T + k, t);
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}
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fmpz_swap(t, T + k);
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for ( ; k < h; k++)
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{
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if ((len - 1) & (WORD(1) << k))
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{
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fmpz_mul(u, y + k, t);
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fmpz_add(t, T + k, u);
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}
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}
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*y = WORD(0);
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_fmpz_vec_clear(y, 2 * h + 2);
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}
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void
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fmpz_poly_evaluate_divconquer_fmpz(fmpz_t res, const fmpz_poly_t poly,
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const fmpz_t a)
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{
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if (fmpz_poly_is_zero(poly))
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{
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fmpz_zero(res);
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return;
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}
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if (res == a)
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{
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fmpz_t t;
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fmpz_init(t);
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_fmpz_poly_evaluate_divconquer_fmpz(t, poly->coeffs, poly->length, a);
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fmpz_swap(res, t);
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fmpz_clear(t);
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}
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else
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_fmpz_poly_evaluate_divconquer_fmpz(res, poly->coeffs, poly->length, a);
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}
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