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Member "gmp-6.2.1/mpn/generic/add_err3_n.c" (14 Nov 2020, 3693 Bytes) of package /linux/misc/gmp-6.2.1.tar.xz:


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    1 /* mpn_add_err3_n -- add_n with three error terms
    2 
    3    Contributed by David Harvey.
    4 
    5    THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE.  IT IS ONLY
    6    SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES.  IN FACT, IT IS ALMOST
    7    GUARANTEED THAT IT'LL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
    8 
    9 Copyright 2011 Free Software Foundation, Inc.
   10 
   11 This file is part of the GNU MP Library.
   12 
   13 The GNU MP Library is free software; you can redistribute it and/or modify
   14 it under the terms of either:
   15 
   16   * the GNU Lesser General Public License as published by the Free
   17     Software Foundation; either version 3 of the License, or (at your
   18     option) any later version.
   19 
   20 or
   21 
   22   * the GNU General Public License as published by the Free Software
   23     Foundation; either version 2 of the License, or (at your option) any
   24     later version.
   25 
   26 or both in parallel, as here.
   27 
   28 The GNU MP Library is distributed in the hope that it will be useful, but
   29 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
   30 or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   31 for more details.
   32 
   33 You should have received copies of the GNU General Public License and the
   34 GNU Lesser General Public License along with the GNU MP Library.  If not,
   35 see https://www.gnu.org/licenses/.  */
   36 
   37 #include "gmp-impl.h"
   38 
   39 /*
   40   Computes:
   41 
   42   (1) {rp,n} := {up,n} + {vp,n} (just like mpn_add_n) with incoming carry cy,
   43   return value is carry out.
   44 
   45   (2) Let c[i+1] = carry from i-th limb addition (c[0] = cy).
   46   Computes c[1]*yp1[n-1] + ... + c[n]*yp1[0],
   47            c[1]*yp2[n-1] + ... + c[n]*yp2[0],
   48            c[1]*yp3[n-1] + ... + c[n]*yp3[0],
   49   stores two-limb results at {ep,2}, {ep+2,2} and {ep+4,2} respectively.
   50 
   51   Requires n >= 1.
   52 
   53   None of the outputs may overlap each other or any of the inputs, except
   54   that {rp,n} may be equal to {up,n} or {vp,n}.
   55 */
   56 mp_limb_t
   57 mpn_add_err3_n (mp_ptr rp, mp_srcptr up, mp_srcptr vp,
   58                 mp_ptr ep, mp_srcptr yp1, mp_srcptr yp2, mp_srcptr yp3,
   59                 mp_size_t n, mp_limb_t cy)
   60 {
   61   mp_limb_t el1, eh1, el2, eh2, el3, eh3, ul, vl, yl1, yl2, yl3, zl1, zl2, zl3, rl, sl, cy1, cy2;
   62 
   63   ASSERT (n >= 1);
   64   ASSERT (MPN_SAME_OR_SEPARATE_P (rp, up, n));
   65   ASSERT (MPN_SAME_OR_SEPARATE_P (rp, vp, n));
   66   ASSERT (! MPN_OVERLAP_P (rp, n, yp1, n));
   67   ASSERT (! MPN_OVERLAP_P (rp, n, yp2, n));
   68   ASSERT (! MPN_OVERLAP_P (rp, n, yp3, n));
   69   ASSERT (! MPN_OVERLAP_P (ep, 6, up, n));
   70   ASSERT (! MPN_OVERLAP_P (ep, 6, vp, n));
   71   ASSERT (! MPN_OVERLAP_P (ep, 6, yp1, n));
   72   ASSERT (! MPN_OVERLAP_P (ep, 6, yp2, n));
   73   ASSERT (! MPN_OVERLAP_P (ep, 6, yp3, n));
   74   ASSERT (! MPN_OVERLAP_P (ep, 6, rp, n));
   75 
   76   yp1 += n - 1;
   77   yp2 += n - 1;
   78   yp3 += n - 1;
   79   el1 = eh1 = 0;
   80   el2 = eh2 = 0;
   81   el3 = eh3 = 0;
   82 
   83   do
   84     {
   85       yl1 = *yp1--;
   86       yl2 = *yp2--;
   87       yl3 = *yp3--;
   88       ul = *up++;
   89       vl = *vp++;
   90 
   91       /* ordinary add_n */
   92       ADDC_LIMB (cy1, sl, ul, vl);
   93       ADDC_LIMB (cy2, rl, sl, cy);
   94       cy = cy1 | cy2;
   95       *rp++ = rl;
   96 
   97       /* update (eh1:el1) */
   98       zl1 = (-cy) & yl1;
   99       el1 += zl1;
  100       eh1 += el1 < zl1;
  101 
  102       /* update (eh2:el2) */
  103       zl2 = (-cy) & yl2;
  104       el2 += zl2;
  105       eh2 += el2 < zl2;
  106 
  107       /* update (eh3:el3) */
  108       zl3 = (-cy) & yl3;
  109       el3 += zl3;
  110       eh3 += el3 < zl3;
  111     }
  112   while (--n);
  113 
  114 #if GMP_NAIL_BITS != 0
  115   eh1 = (eh1 << GMP_NAIL_BITS) + (el1 >> GMP_NUMB_BITS);
  116   el1 &= GMP_NUMB_MASK;
  117   eh2 = (eh2 << GMP_NAIL_BITS) + (el2 >> GMP_NUMB_BITS);
  118   el2 &= GMP_NUMB_MASK;
  119   eh3 = (eh3 << GMP_NAIL_BITS) + (el3 >> GMP_NUMB_BITS);
  120   el3 &= GMP_NUMB_MASK;
  121 #endif
  122 
  123   ep[0] = el1;
  124   ep[1] = eh1;
  125   ep[2] = el2;
  126   ep[3] = eh2;
  127   ep[4] = el3;
  128   ep[5] = eh3;
  129 
  130   return cy;
  131 }