116 lines
3.0 KiB
C
116 lines
3.0 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 2009 Jason Moxham
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******************************************************************************/
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#include "gmp.h"
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#include "flint.h"
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#include "mpn_extras.h"
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/* ret + (xp,n) = (yp,n)*(zp,n) % 2^b+1
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needs (tp,2n) temp space, everything reduced mod 2^b
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inputs, outputs are fully reduced
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NOTE: 2n is not the same as 2b rounded up to nearest limb
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*/
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static __inline__ int
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flint_mpn_mulmod_2expp1_internal(mp_ptr xp, mp_srcptr yp, mp_srcptr zp,
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mp_bitcnt_t b, mp_ptr tp)
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{
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mp_size_t n, k;
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mp_limb_t c;
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n = BITS_TO_LIMBS(b);
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k = GMP_NUMB_BITS * n - b;
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mpn_mul_n(tp, yp, zp, n);
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if (k == 0)
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{
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c = mpn_sub_n(xp, tp, tp + n, n);
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return mpn_add_1 (xp, xp, n, c);
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}
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c = tp[n - 1];
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tp[n - 1] &= GMP_NUMB_MASK >> k;
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#if HAVE_NATIVE_mpn_sublsh_nc
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c = mpn_sublsh_nc (xp, tp, tp + n, n, k, c);
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#else
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{
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mp_limb_t c1;
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c1 = mpn_lshift (tp + n, tp + n, n, k);
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tp[n] |= c >> (GMP_NUMB_BITS - k);
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c = mpn_sub_n (xp, tp, tp + n, n) + c1;
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}
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#endif
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c = mpn_add_1 (xp, xp, n, c);
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xp[n - 1] &= GMP_NUMB_MASK >> k;
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return c;
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}
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/* c is the top bits of the inputs, must be fully reduced */
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int
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flint_mpn_mulmod_2expp1_basecase (mp_ptr xp, mp_srcptr yp, mp_srcptr zp, int c,
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mp_bitcnt_t b, mp_ptr tp)
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{
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int cy, cz;
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mp_size_t n, k;
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cy = c & 2;
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cz = c & 1;
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n = BITS_TO_LIMBS(b);
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k = GMP_NUMB_BITS * n - b;
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if (cy == 0)
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{
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if (cz == 0)
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{
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c = flint_mpn_mulmod_2expp1_internal(xp, yp, zp, b, tp);
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}
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else
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{
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c = mpn_neg_n(xp, yp, n);
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c = mpn_add_1 (xp, xp, n, c);
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xp[n - 1] &= GMP_NUMB_MASK >> k;
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}
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}
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else
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{
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if (cz == 0)
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{
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c = mpn_neg_n(xp, zp, n);
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c = mpn_add_1(xp, xp, n, c);
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xp[n - 1] &= GMP_NUMB_MASK >> k;
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}
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else
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{
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c = 0;
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xp[0] = 1;
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flint_mpn_zero(xp + 1, n - 1);
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}
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}
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return c;
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}
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