116 lines
3.4 KiB
C
116 lines
3.4 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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Copyright (C) 2012 William Hart
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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 "fmpz_vec.h"
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#include "fmpz_poly.h"
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#include "fmpz_mod_poly.h"
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fmpz_poly_struct ** _fmpz_mod_poly_tree_alloc(slong len)
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{
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fmpz_poly_struct ** tree = NULL;
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if (len)
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{
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slong i, j, height = FLINT_CLOG2(len);
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tree = flint_malloc(sizeof(fmpz_poly_struct *) * (height + 1));
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for (i = 0; i <= height; i++, len = (len + 1)/2)
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{
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tree[i] = flint_malloc(sizeof(fmpz_poly_struct) * len);
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for (j = 0; j < len; j++)
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fmpz_poly_init(tree[i] + j);
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}
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}
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return tree;
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}
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void _fmpz_mod_poly_tree_free(fmpz_poly_struct ** tree, slong len)
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{
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if (len)
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{
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slong i, j, height = FLINT_CLOG2(len);
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for (i = 0; i <= height; i++, len = (len + 1)/2)
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{
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for (j = 0; j < len; j++)
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fmpz_poly_clear(tree[i] + j);
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flint_free(tree[i]);
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}
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flint_free(tree);
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}
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}
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void
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_fmpz_mod_poly_tree_build(fmpz_poly_struct ** tree, const fmpz * roots, slong len, const fmpz_t mod)
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{
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slong height, pow, left, i;
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fmpz_poly_struct * 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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fmpz_poly_set_coeff_ui(tree[0] + i, 1, 1);
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fmpz_negmod((tree[0] + i)->coeffs, roots + i, mod);
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}
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for (i = 0; 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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fmpz_poly_fit_length(pb, pa->length + (pa + 1)->length - 1);
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_fmpz_mod_poly_mul(pb->coeffs, pa->coeffs, pa->length, (pa + 1)->coeffs, (pa + 1)->length, mod);
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_fmpz_poly_set_length(pb, pa->length + (pa + 1)->length - 1);
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left -= 2 * pow;
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pa += 2;
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pb += 1;
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}
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if (left > pow)
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{
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fmpz_poly_fit_length(pb, pa->length + (pa + 1)->length - 1);
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_fmpz_mod_poly_mul(pb->coeffs, pa->coeffs, pa->length, (pa + 1)->coeffs, (pa + 1)->length, mod);
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_fmpz_poly_set_length(pb, pa->length + (pa + 1)->length - 1);
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} else if (left > 0)
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fmpz_poly_set(pb, pa);
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}
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}
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