154 lines
4.2 KiB
C
154 lines
4.2 KiB
C
/* mpn_mulmod_2expp1
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Copyright 2009 Jason Moxham
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This file is part of the MPIR Library.
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The MPIR 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
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by the Free Software Foundation; either version 2.1 of the License, or (at
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your option) any later version.
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The MPIR 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 MPIR Library; see the file COPYING.LIB. If not, write
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to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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Boston, MA 02110-1301, USA.
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*/
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#include "mpir.h"
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#include "gmp-impl.h"
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#include "longlong.h"
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// k 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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static mp_size_t tab[]={0,0,0,2632,304,448,1024,2304,6400,11264,45056,114688,327680,1310720,3145728,12582912 };// OUT OF DATE
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// from K8 old mul_fft_table 560 1184 1856 3840
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// these thresholds could do with tuning , and extending
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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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inline static int
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mpn_mulmod_2expp1_internal (mp_ptr xp, mp_srcptr yp, mp_srcptr zp,
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gmp_ui 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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ASSERT (b > 0);
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ASSERT (n > 0);
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ASSERT_MPN (yp, n);
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ASSERT_MPN (zp, n);
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ASSERT (!MPN_OVERLAP_P (tp, 2 * n, yp, n));
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ASSERT (!MPN_OVERLAP_P (tp, 2 * n, zp, n));
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ASSERT (!MPN_OVERLAP_P (xp, n, yp, n));
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ASSERT (!MPN_OVERLAP_P (xp, n, zp, n));
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ASSERT (MPN_SAME_OR_SEPARATE_P (xp, tp, n));
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ASSERT (MPN_SAME_OR_SEPARATE_P (xp, tp + n, n));
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ASSERT (k == 0 || yp[n - 1] >> (GMP_NUMB_BITS - k) == 0);
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ASSERT (k == 0 || zp[n - 1] >> (GMP_NUMB_BITS - k) == 0);
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#if 0 && GMP_NAIL_BITS == 0
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// mpn_mul_fft dont do nails
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// fft has changed cant use this like this , but can use it HOW?
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if (k == 0 && n % 8 == 0)
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{
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count_trailing_zeros (c, n);
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if (c > 15)
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c = 15;
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for (c = c; c > 2; c--)
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if (n >= tab[c])
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return mpn_mul_fft (xp, n, yp, n, zp, n, c);
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}
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#endif
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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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mpn_mulmod_2expp1 (mp_ptr xp, mp_srcptr yp, mp_srcptr zp, int c,
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gmp_ui 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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ASSERT (b > 0);
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ASSERT (n > 0);
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ASSERT_MPN (yp, n);
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ASSERT_MPN (zp, n);
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ASSERT (!MPN_OVERLAP_P (tp, 2 * n, yp, n));
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ASSERT (!MPN_OVERLAP_P (tp, 2 * n, zp, n));
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ASSERT (MPN_SAME_OR_SEPARATE_P (xp, tp, n));
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ASSERT (MPN_SAME_OR_SEPARATE_P (xp, tp + n, n));
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ASSERT (k == 0 || yp[n - 1] >> (GMP_NUMB_BITS - k) == 0);
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ASSERT (k == 0 || zp[n - 1] >> (GMP_NUMB_BITS - k) == 0);
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#if WANT_ASSERT
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mp_size_t t;
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t = n;
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MPN_NORMALIZE (yp, t);
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ASSERT (cy == 0 || t == 0);
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t = n;
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MPN_NORMALIZE (zp, t);
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ASSERT (cz == 0 || t == 0);
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#endif
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if (LIKELY (cy == 0))
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{
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if (LIKELY (cz == 0))
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{
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c = 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 (LIKELY (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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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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