92 lines
2.5 KiB
C
92 lines
2.5 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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Multi-exponentiation code based on Paul Zimmermann's implementation
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of the double factorial
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Copyright (C) 2009, 2010 Paul Zimmermann
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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 "fmpz.h"
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#include "fmpz_vec.h"
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void
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_fmpz_factor_eval_multiexp(fmpz_t res, const fmpz * p, const ulong * e, slong len)
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{
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slong i, j;
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ulong mask, emax;
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fmpz * q;
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fmpz_t tmp;
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if (len <= 1)
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{
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if (len < 1)
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fmpz_one(res);
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else
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fmpz_pow_ui(res, p, e[0]);
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return;
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}
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q = flint_malloc(sizeof(fmpz) * len);
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emax = e[0];
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for (i = 1; i < len; i++)
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emax = FLINT_MAX(emax, e[i]);
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for (mask = 1; emax >= (mask << 1); mask <<= 1);
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fmpz_init(tmp);
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fmpz_one(res);
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while (mask)
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{
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for (i = 0, j = 0; i < len; i++)
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if (e[i] & mask)
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q[j++] = p[i];
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_fmpz_vec_prod(tmp, q, j);
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fmpz_mul(res, res, res);
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fmpz_mul(res, res, tmp);
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mask >>= 1;
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}
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fmpz_clear(tmp);
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flint_free(q);
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}
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void
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fmpz_factor_expand_multiexp(fmpz_t n, const fmpz_factor_t factor)
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{
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if (factor->num != 0 && factor->p[0] == 2)
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{
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_fmpz_factor_eval_multiexp(n, factor->p + 1, factor->exp + 1, factor->num - 1);
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fmpz_mul_2exp(n, n, factor->exp[0]);
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}
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else
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_fmpz_factor_eval_multiexp(n, factor->p, factor->exp, factor->num);
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fmpz_mul_si(n, n, factor->sign);
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}
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