92 lines
2.7 KiB
C
92 lines
2.7 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 William Hart
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******************************************************************************/
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#include <stdlib.h>
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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 "mpn_extras.h"
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mp_size_t flint_mpn_gcd_full(mp_ptr arrayg,
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mp_ptr array1, mp_size_t limbs1, mp_ptr array2, mp_size_t limbs2)
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{
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mp_size_t s1 = 0, s2 = 0, m, b1, b2, mb, len1, len2, leng;
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mp_ptr in1, in2;
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mp_limb_t cy;
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/* find maximum power of 2 dividing inputs */
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b1 = mpn_scan1(array1 + s1, 0);
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b2 = mpn_scan1(array2 + s2, 0);
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/* get bit shifts [0, FLINT_BITS) and limb shifts */
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mb = FLINT_MIN(b1, b2) % FLINT_BITS;
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s1 = b1 / FLINT_BITS; b1 = b1 % FLINT_BITS; len1 = limbs1 - s1;
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s2 = b2 / FLINT_BITS; b2 = b2 % FLINT_BITS; len2 = limbs2 - s2;
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m = FLINT_MIN(s1, s2);
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/* this many output limbs will be zero */
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flint_mpn_zero(arrayg, m);
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/* set in1 to shifted array1 */
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if (b1 == 0)
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in1 = array1 + s1;
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else
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{
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in1 = flint_malloc(len1*sizeof(mp_limb_t));
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mpn_rshift(in1, array1 + s1, len1, b1);
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len1 -= (in1[len1 - 1] == 0);
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}
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/* set in2 to shifted array2 */
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if (b2 == 0)
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in2 = array2 + s2;
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else
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{
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in2 = flint_malloc(len2*sizeof(mp_limb_t));
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mpn_rshift(in2, array2 + s2, len2, b2);
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len2 -= (in2[len2 - 1] == 0);
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}
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/* compute gcd of shifted values */
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if (len1 >= len2)
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leng = mpn_gcd(arrayg + m, in1, len1, in2, len2);
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else
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leng = mpn_gcd(arrayg + m, in2, len2, in1, len1);
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if (mb) /* shift back by mb bits */
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{
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cy = mpn_lshift(arrayg + m, arrayg + m, leng, mb);
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if (cy)
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arrayg[m + leng++] = cy;
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}
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/* clean up */
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if (b1) flint_free(in1);
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if (b2) flint_free(in2);
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/* return total number of limbs in output */
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return m + leng;
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}
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