github.com/aergoio/aergo@v1.3.1/libtool/src/gmp-6.1.2/mpn/generic/toom_eval_pm2exp.c (about)

     1  /* mpn_toom_eval_pm2exp -- Evaluate a polynomial in +2^k and -2^k
     2  
     3     Contributed to the GNU project by Niels Möller
     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 WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
     8  
     9  Copyright 2009 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  
    38  #include "gmp.h"
    39  #include "gmp-impl.h"
    40  
    41  /* Evaluates a polynomial of degree k > 2, in the points +2^shift and -2^shift. */
    42  int
    43  mpn_toom_eval_pm2exp (mp_ptr xp2, mp_ptr xm2, unsigned k,
    44  		      mp_srcptr xp, mp_size_t n, mp_size_t hn, unsigned shift,
    45  		      mp_ptr tp)
    46  {
    47    unsigned i;
    48    int neg;
    49  #if HAVE_NATIVE_mpn_addlsh_n
    50    mp_limb_t cy;
    51  #endif
    52  
    53    ASSERT (k >= 3);
    54    ASSERT (shift*k < GMP_NUMB_BITS);
    55  
    56    ASSERT (hn > 0);
    57    ASSERT (hn <= n);
    58  
    59    /* The degree k is also the number of full-size coefficients, so
    60     * that last coefficient, of size hn, starts at xp + k*n. */
    61  
    62  #if HAVE_NATIVE_mpn_addlsh_n
    63    xp2[n] = mpn_addlsh_n (xp2, xp, xp + 2*n, n, 2*shift);
    64    for (i = 4; i < k; i += 2)
    65      xp2[n] += mpn_addlsh_n (xp2, xp2, xp + i*n, n, i*shift);
    66  
    67    tp[n] = mpn_lshift (tp, xp+n, n, shift);
    68    for (i = 3; i < k; i+= 2)
    69      tp[n] += mpn_addlsh_n (tp, tp, xp+i*n, n, i*shift);
    70  
    71    if (k & 1)
    72      {
    73        cy = mpn_addlsh_n (tp, tp, xp+k*n, hn, k*shift);
    74        MPN_INCR_U (tp + hn, n+1 - hn, cy);
    75      }
    76    else
    77      {
    78        cy = mpn_addlsh_n (xp2, xp2, xp+k*n, hn, k*shift);
    79        MPN_INCR_U (xp2 + hn, n+1 - hn, cy);
    80      }
    81  
    82  #else /* !HAVE_NATIVE_mpn_addlsh_n */
    83    xp2[n] = mpn_lshift (tp, xp+2*n, n, 2*shift);
    84    xp2[n] += mpn_add_n (xp2, xp, tp, n);
    85    for (i = 4; i < k; i += 2)
    86      {
    87        xp2[n] += mpn_lshift (tp, xp + i*n, n, i*shift);
    88        xp2[n] += mpn_add_n (xp2, xp2, tp, n);
    89      }
    90  
    91    tp[n] = mpn_lshift (tp, xp+n, n, shift);
    92    for (i = 3; i < k; i+= 2)
    93      {
    94        tp[n] += mpn_lshift (xm2, xp + i*n, n, i*shift);
    95        tp[n] += mpn_add_n (tp, tp, xm2, n);
    96      }
    97  
    98    xm2[hn] = mpn_lshift (xm2, xp + k*n, hn, k*shift);
    99    if (k & 1)
   100      mpn_add (tp, tp, n+1, xm2, hn+1);
   101    else
   102      mpn_add (xp2, xp2, n+1, xm2, hn+1);
   103  #endif /* !HAVE_NATIVE_mpn_addlsh_n */
   104  
   105    neg = (mpn_cmp (xp2, tp, n + 1) < 0) ? ~0 : 0;
   106  
   107  #if HAVE_NATIVE_mpn_add_n_sub_n
   108    if (neg)
   109      mpn_add_n_sub_n (xp2, xm2, tp, xp2, n + 1);
   110    else
   111      mpn_add_n_sub_n (xp2, xm2, xp2, tp, n + 1);
   112  #else /* !HAVE_NATIVE_mpn_add_n_sub_n */
   113    if (neg)
   114      mpn_sub_n (xm2, tp, xp2, n + 1);
   115    else
   116      mpn_sub_n (xm2, xp2, tp, n + 1);
   117  
   118    mpn_add_n (xp2, xp2, tp, n + 1);
   119  #endif /* !HAVE_NATIVE_mpn_add_n_sub_n */
   120  
   121    /* FIXME: the following asserts are useless if (k+1)*shift >= GMP_LIMB_BITS */
   122    ASSERT ((k+1)*shift >= GMP_LIMB_BITS ||
   123  	  xp2[n] < ((CNST_LIMB(1)<<((k+1)*shift))-1)/((CNST_LIMB(1)<<shift)-1));
   124    ASSERT ((k+2)*shift >= GMP_LIMB_BITS ||
   125  	  xm2[n] < ((CNST_LIMB(1)<<((k+2)*shift))-((k&1)?(CNST_LIMB(1)<<shift):1))/((CNST_LIMB(1)<<(2*shift))-1));
   126  
   127    return neg;
   128  }