124 lines
3.1 KiB
C
124 lines
3.1 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) 2011 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_vec.h"
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#include "nmod_poly.h"
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mp_ptr * _nmod_poly_tree_alloc(slong len)
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{
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mp_ptr * tree = NULL;
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if (len)
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{
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slong i, height = FLINT_CLOG2(len);
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tree = flint_malloc(sizeof(mp_ptr) * (height + 1));
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for (i = 0; i <= height; i++)
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tree[i] = _nmod_vec_init(len + (len >> i) + 1);
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}
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return tree;
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}
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void _nmod_poly_tree_free(mp_ptr * tree, slong len)
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{
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if (len)
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{
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slong i, height = FLINT_CLOG2(len);
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for (i = 0; i <= height; i++)
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flint_free(tree[i]);
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flint_free(tree);
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}
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}
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void
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_nmod_poly_tree_build(mp_ptr * tree, mp_srcptr roots, slong len, nmod_t mod)
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{
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slong height, pow, left, i;
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mp_ptr pa, pb;
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if (len == 0)
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return;
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height = FLINT_CLOG2(len);
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/* zeroth level, (x-a) */
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for (i = 0; i < len; i++)
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{
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tree[0][2 * i + 1] = 1;
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tree[0][2 * i] = nmod_neg(roots[i], mod);
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}
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/* first level, (x-a)(x-b) = x^2 + (-a-b)*x + a*b */
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if (height > 1)
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{
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pa = tree[1];
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for (i = 0; i < len / 2; i++)
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{
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mp_limb_t a, b;
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a = roots[2 * i];
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b = roots[2 * i + 1];
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pa[3 * i] = nmod_mul(a, b, mod);
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pa[3 * i + 1] = nmod_neg(nmod_add(a, b, mod), mod);
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pa[3 * i + 2] = 1;
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}
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if (len & 1)
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{
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pa[3 * (len / 2)] = nmod_neg(roots[len-1], mod);
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pa[3 * (len / 2) + 1] = 1;
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}
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}
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for (i = 1; i < height - 1; i++)
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{
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left = len;
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pow = WORD(1) << i;
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pa = tree[i];
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pb = tree[i + 1];
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while (left >= 2 * pow)
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{
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_nmod_poly_mul(pb, pa, pow + 1, pa + pow + 1, pow + 1, mod);
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left -= 2 * pow;
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pa += 2 * pow + 2;
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pb += 2 * pow + 1;
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}
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if (left > pow)
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_nmod_poly_mul(pb, pa, pow + 1, pa + pow + 1, left - pow + 1, mod);
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else if (left > 0)
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_nmod_vec_set(pb, pa, left + 1);
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}
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}
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