source/libs/gmp/gmp-src/mpn/generic/add_n_sub_n.c

   1 /* mpn_add_n_sub_n -- Add and Subtract two limb vectors of equal, non-zero length.
   2
   3    THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE.  IT IS ONLY
   4    SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES.  IN FACT, IT IS ALMOST
   5    GUARANTEED THAT IT'LL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
   6
   7 Copyright 1999-2001, 2006 Free Software Foundation, Inc.
   8
   9 This file is part of the GNU MP Library.
  10
  11 The GNU MP Library is free software; you can redistribute it and/or modify
  12 it under the terms of either:
  13
  14   * the GNU Lesser General Public License as published by the Free
  15     Software Foundation; either version 3 of the License, or (at your
  16     option) any later version.
  17
  18 or
  19
  20   * the GNU General Public License as published by the Free Software
  21     Foundation; either version 2 of the License, or (at your option) any
  22     later version.
  23
  24 or both in parallel, as here.
  25
  26 The GNU MP Library is distributed in the hope that it will be useful, but
  27 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  28 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  29 for more details.
  30
  31 You should have received copies of the GNU General Public License and the
  32 GNU Lesser General Public License along with the GNU MP Library.  If not,
  33 see https://www.gnu.org/licenses/.  */
  34
  35 #include "gmp.h"
  36 #include "gmp-impl.h"
  37
  38 #ifndef L1_CACHE_SIZE
  39 #define L1_CACHE_SIZE 8192      /* only 68040 has less than this */
  40 #endif
  41
  42 #define PART_SIZE (L1_CACHE_SIZE / GMP_LIMB_BYTES / 6)
  43
  44
  45 /* mpn_add_n_sub_n.
  46    r1[] = s1[] + s2[]
  47    r2[] = s1[] - s2[]
  48    All operands have n limbs.
  49    In-place operations allowed.  */
  50 mp_limb_t
  51 mpn_add_n_sub_n (mp_ptr r1p, mp_ptr r2p, mp_srcptr s1p, mp_srcptr s2p, mp_size_t n)
  52 {
  53   mp_limb_t acyn, acyo;         /* carry for add */
  54   mp_limb_t scyn, scyo;         /* carry for subtract */
  55   mp_size_t off;                /* offset in operands */
  56   mp_size_t this_n;             /* size of current chunk */
  57
  58   /* We alternatingly add and subtract in chunks that fit into the (L1)
  59      cache.  Since the chunks are several hundred limbs, the function call
  60      overhead is insignificant, but we get much better locality.  */
  61
  62   /* We have three variant of the inner loop, the proper loop is chosen
  63      depending on whether r1 or r2 are the same operand as s1 or s2.  */
  64
  65   if (r1p != s1p && r1p != s2p)
  66     {
  67       /* r1 is not identical to either input operand.  We can therefore write
  68          to r1 directly, without using temporary storage.  */
  69       acyo = 0;
  70       scyo = 0;
  71       for (off = 0; off < n; off += PART_SIZE)
  72         {
  73           this_n = MIN (n - off, PART_SIZE);
  74 #if HAVE_NATIVE_mpn_add_nc
  75           acyo = mpn_add_nc (r1p + off, s1p + off, s2p + off, this_n, acyo);
  76 #else
  77           acyn = mpn_add_n (r1p + off, s1p + off, s2p + off, this_n);
  78           acyo = acyn + mpn_add_1 (r1p + off, r1p + off, this_n, acyo);
  79 #endif
  80 #if HAVE_NATIVE_mpn_sub_nc
  81           scyo = mpn_sub_nc (r2p + off, s1p + off, s2p + off, this_n, scyo);
  82 #else
  83           scyn = mpn_sub_n (r2p + off, s1p + off, s2p + off, this_n);
  84           scyo = scyn + mpn_sub_1 (r2p + off, r2p + off, this_n, scyo);
  85 #endif
  86         }
  87     }
  88   else if (r2p != s1p && r2p != s2p)
  89     {
  90       /* r2 is not identical to either input operand.  We can therefore write
  91          to r2 directly, without using temporary storage.  */
  92       acyo = 0;
  93       scyo = 0;
  94       for (off = 0; off < n; off += PART_SIZE)
  95         {
  96           this_n = MIN (n - off, PART_SIZE);
  97 #if HAVE_NATIVE_mpn_sub_nc
  98           scyo = mpn_sub_nc (r2p + off, s1p + off, s2p + off, this_n, scyo);
  99 #else
 100           scyn = mpn_sub_n (r2p + off, s1p + off, s2p + off, this_n);
 101           scyo = scyn + mpn_sub_1 (r2p + off, r2p + off, this_n, scyo);
 102 #endif
 103 #if HAVE_NATIVE_mpn_add_nc
 104           acyo = mpn_add_nc (r1p + off, s1p + off, s2p + off, this_n, acyo);
 105 #else
 106           acyn = mpn_add_n (r1p + off, s1p + off, s2p + off, this_n);
 107           acyo = acyn + mpn_add_1 (r1p + off, r1p + off, this_n, acyo);
 108 #endif
 109         }
 110     }
 111   else
 112     {
 113       /* r1 and r2 are identical to s1 and s2 (r1==s1 and r2==s2 or vice versa)
 114          Need temporary storage.  */
 115       mp_limb_t tp[PART_SIZE];
 116       acyo = 0;
 117       scyo = 0;
 118       for (off = 0; off < n; off += PART_SIZE)
 119         {
 120           this_n = MIN (n - off, PART_SIZE);
 121 #if HAVE_NATIVE_mpn_add_nc
 122           acyo = mpn_add_nc (tp, s1p + off, s2p + off, this_n, acyo);
 123 #else
 124           acyn = mpn_add_n (tp, s1p + off, s2p + off, this_n);
 125           acyo = acyn + mpn_add_1 (tp, tp, this_n, acyo);
 126 #endif
 127 #if HAVE_NATIVE_mpn_sub_nc
 128           scyo = mpn_sub_nc (r2p + off, s1p + off, s2p + off, this_n, scyo);
 129 #else
 130           scyn = mpn_sub_n (r2p + off, s1p + off, s2p + off, this_n);
 131           scyo = scyn + mpn_sub_1 (r2p + off, r2p + off, this_n, scyo);
 132 #endif
 133           MPN_COPY (r1p + off, tp, this_n);
 134         }
 135     }
 136
 137   return 2 * acyo + scyo;
 138 }
 139
 140 #ifdef MAIN
 141 #include <stdlib.h>
 142 #include <stdio.h>
 143 #include "timing.h"
 144
 145 long cputime ();
 146
 147 int
 148 main (int argc, char **argv)
 149 {
 150   mp_ptr r1p, r2p, s1p, s2p;
 151   double t;
 152   mp_size_t n;
 153
 154   n = strtol (argv[1], 0, 0);
 155
 156   r1p = malloc (n * GMP_LIMB_BYTES);
 157   r2p = malloc (n * GMP_LIMB_BYTES);
 158   s1p = malloc (n * GMP_LIMB_BYTES);
 159   s2p = malloc (n * GMP_LIMB_BYTES);
 160   TIME (t,(mpn_add_n(r1p,s1p,s2p,n),mpn_sub_n(r1p,s1p,s2p,n)));
 161   printf ("              separate add and sub: %.3f\n", t);
 162   TIME (t,mpn_add_n_sub_n(r1p,r2p,s1p,s2p,n));
 163   printf ("combined addsub separate variables: %.3f\n", t);
 164   TIME (t,mpn_add_n_sub_n(r1p,r2p,r1p,s2p,n));
 165   printf ("        combined addsub r1 overlap: %.3f\n", t);
 166   TIME (t,mpn_add_n_sub_n(r1p,r2p,r1p,s2p,n));
 167   printf ("        combined addsub r2 overlap: %.3f\n", t);
 168   TIME (t,mpn_add_n_sub_n(r1p,r2p,r1p,r2p,n));
 169   printf ("          combined addsub in-place: %.3f\n", t);
 170
 171   return 0;
 172 }
 173 #endif