mirror of
https://github.com/vale981/arb
synced 2025-03-05 09:21:38 -05:00
121 lines
3.2 KiB
C
121 lines
3.2 KiB
C
/*=============================================================================
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This file is part of ARB.
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ARB 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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ARB 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 ARB; 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 "arb_poly.h"
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arb_ptr * _arb_poly_tree_alloc(slong len)
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{
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arb_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(arb_ptr) * (height + 1));
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for (i = 0; i <= height; i++)
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tree[i] = _arb_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 _arb_poly_tree_free(arb_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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_arb_vec_clear(tree[i], len + (len >> i) + 1);
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flint_free(tree);
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}
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}
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void
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_arb_poly_tree_build(arb_ptr * tree, arb_srcptr roots, slong len, slong prec)
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{
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slong height, pow, left, i;
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arb_ptr pa, pb;
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arb_srcptr a, b;
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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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arb_one(tree[0] + (2 * i + 1));
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arb_neg(tree[0] + (2 * i), roots + i);
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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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a = (arb_srcptr) (roots + (2 * i));
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b = (arb_srcptr) (roots + (2 * i + 1));
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arb_mul(pa + (3 * i), a, b, prec);
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arb_add(pa + (3 * i + 1), a, b, prec);
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arb_neg(pa + (3 * i + 1), pa + (3 * i + 1));
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arb_one(pa + (3 * i + 2));
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}
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if (len & 1)
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{
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arb_neg(pa + (3 * (len / 2)), roots + len - 1);
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arb_one(pa + (3 * (len / 2) + 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 = 1L << 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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_arb_poly_mul_monic(pb, pa, pow + 1, pa + pow + 1, pow + 1, prec);
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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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{
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_arb_poly_mul_monic(pb, pa, pow + 1, pa + pow + 1, left - pow + 1, prec);
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}
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else if (left > 0)
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_arb_vec_set(pb, pa, left + 1);
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}
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}
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