99 lines
2.8 KiB
C
99 lines
2.8 KiB
C
/* mpz_prodlimps(RESULT, V, LEN) -- Set RESULT to V[0]*V[1]*...*V[LEN-1].
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Contributed to the GNU project by Marco Bodrato.
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THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE.
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IT IS ONLY SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES.
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IN FACT, IT IS ALMOST GUARANTEED THAT IT WILL CHANGE OR
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DISAPPEAR IN A FUTURE GNU MP RELEASE.
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Copyright 2010, 2011, 2012 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 3 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
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#include "mpir.h"
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#include "gmp-impl.h"
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/*********************************************************/
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/* Section list-prod: product of a list -> mpz_t */
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/*********************************************************/
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/* FIXME: should be tuned */
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#ifndef RECURSIVE_PROD_THRESHOLD
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#define RECURSIVE_PROD_THRESHOLD (MUL_KARATSUBA_THRESHOLD)
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#endif
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/* Computes the product of the j>1 limbs pointed by factors, puts the
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* result in x. It assumes that all limbs are non-zero. Above
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* Karatsuba's threshold it uses a binary splitting startegy, to gain
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* speed by the asymptotically fast multiplication algorithms.
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*
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* The list in {factors, j} is overwritten.
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* Returns the size of the result
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*/
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mp_size_t
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mpz_prodlimbs (mpz_ptr x, mp_ptr factors, mp_size_t j)
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{
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mp_limb_t cy;
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mp_size_t size, i;
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mp_ptr prod;
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ASSERT (j > 1);
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ASSERT (RECURSIVE_PROD_THRESHOLD > 3);
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if (BELOW_THRESHOLD (j, RECURSIVE_PROD_THRESHOLD)) {
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j--;
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size = 1;
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for (i = 1; i < j; i++)
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{
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cy = mpn_mul_1 (factors, factors, size, factors[i]);
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factors[size] = cy;
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size += cy != 0;
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};
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prod = MPZ_NEWALLOC (x, size + 1);
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cy = mpn_mul_1 (prod, factors, size, factors[i]);
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prod[size] = cy;
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return SIZ (x) = size + (cy != 0);
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} else {
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mpz_t x1, x2;
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TMP_DECL;
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i = j >> 1;
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j -= i;
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TMP_MARK;
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MPZ_TMP_INIT (x2, j);
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PTR (x1) = factors + i;
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ALLOC (x1) = j;
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j = mpz_prodlimbs (x2, factors + i, j);
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i = mpz_prodlimbs (x1, factors, i);
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size = i + j;
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prod = MPZ_NEWALLOC (x, size);
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if (i >= j)
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cy = mpn_mul (prod, PTR(x1), i, PTR(x2), j);
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else
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cy = mpn_mul (prod, PTR(x2), j, PTR(x1), i);
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TMP_FREE;
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return SIZ (x) = size - (cy == 0);
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}
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}
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