138 lines
4.0 KiB
C
138 lines
4.0 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) 2012 Fredrik Johansson
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******************************************************************************/
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#include <gmp.h>
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#include "flint.h"
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#include "ulong_extras.h"
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#include "nmod_poly.h"
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/* This gives some speedup for small lengths. */
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static __inline__ void _nmod_poly_rem_2(mp_ptr r, mp_srcptr a, slong al,
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mp_srcptr b, slong bl, nmod_t mod)
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{
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if (al == 2)
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r[0] = nmod_sub(a[0], nmod_mul(a[1], b[0], mod), mod);
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else
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_nmod_poly_rem(r, a, al, b, bl, mod);
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}
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void
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_nmod_poly_evaluate_nmod_vec_fast_precomp(mp_ptr vs, mp_srcptr poly,
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slong plen, const mp_ptr * tree, slong len, nmod_t mod)
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{
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slong height, i, j, pow, left;
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slong tree_height;
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slong tlen;
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mp_ptr t, u, swap, pa, pb, pc;
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/* avoid worrying about some degenerate cases */
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if (len < 2 || plen < 2)
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{
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if (len == 1)
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vs[0] = _nmod_poly_evaluate_nmod(poly, plen,
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nmod_neg(tree[0][0], mod), mod);
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else if (len != 0 && plen == 0)
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_nmod_vec_zero(vs, len);
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else if (len != 0 && plen == 1)
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for (i = 0; i < len; i++)
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vs[i] = poly[0];
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return;
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}
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t = _nmod_vec_init(len);
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u = _nmod_vec_init(len);
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left = len;
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/* Initial reduction. We allow the polynomial to be larger
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or smaller than the number of points. */
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height = FLINT_BIT_COUNT(plen - 1) - 1;
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tree_height = FLINT_CLOG2(len);
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while (height >= tree_height)
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height--;
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pow = WORD(1) << height;
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for (i = j = 0; i < len; i += pow, j += (pow + 1))
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{
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tlen = ((i + pow) <= len) ? pow : len % pow;
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_nmod_poly_rem(t + i, poly, plen, tree[height] + j, tlen + 1, mod);
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}
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for (i = height - 1; i >= 0; i--)
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{
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pow = WORD(1) << i;
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left = len;
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pa = tree[i];
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pb = t;
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pc = u;
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while (left >= 2 * pow)
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{
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_nmod_poly_rem_2(pc, pb, 2 * pow, pa, pow + 1, mod);
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_nmod_poly_rem_2(pc + pow, pb, 2 * pow, pa + pow + 1, pow + 1, mod);
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pa += 2 * pow + 2;
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pb += 2 * pow;
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pc += 2 * pow;
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left -= 2 * pow;
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}
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if (left > pow)
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{
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_nmod_poly_rem(pc, pb, left, pa, pow + 1, mod);
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_nmod_poly_rem(pc + pow, pb, left, pa + pow + 1, left - pow + 1, mod);
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}
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else if (left > 0)
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_nmod_vec_set(pc, pb, left);
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swap = t;
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t = u;
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u = swap;
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}
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_nmod_vec_set(vs, t, len);
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_nmod_vec_clear(t);
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_nmod_vec_clear(u);
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}
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void _nmod_poly_evaluate_nmod_vec_fast(mp_ptr ys, mp_srcptr poly, slong plen,
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mp_srcptr xs, slong n, nmod_t mod)
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{
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mp_ptr * tree;
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tree = _nmod_poly_tree_alloc(n);
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_nmod_poly_tree_build(tree, xs, n, mod);
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_nmod_poly_evaluate_nmod_vec_fast_precomp(ys, poly, plen, tree, n, mod);
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_nmod_poly_tree_free(tree, n);
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}
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void
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nmod_poly_evaluate_nmod_vec_fast(mp_ptr ys,
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const nmod_poly_t poly, mp_srcptr xs, slong n)
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{
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_nmod_poly_evaluate_nmod_vec_fast(ys, poly->coeffs,
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poly->length, xs, n, poly->mod);
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}
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