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

     1  /* mpn_popcount, mpn_hamdist -- mpn bit population count/hamming distance.
     2  
     3  Copyright 1994, 1996, 2000-2002, 2005, 2011, 2012 Free Software Foundation,
     4  Inc.
     5  
     6  This file is part of the GNU MP Library.
     7  
     8  The GNU MP Library is free software; you can redistribute it and/or modify
     9  it under the terms of either:
    10  
    11    * the GNU Lesser General Public License as published by the Free
    12      Software Foundation; either version 3 of the License, or (at your
    13      option) any later version.
    14  
    15  or
    16  
    17    * the GNU General Public License as published by the Free Software
    18      Foundation; either version 2 of the License, or (at your option) any
    19      later version.
    20  
    21  or both in parallel, as here.
    22  
    23  The GNU MP Library is distributed in the hope that it will be useful, but
    24  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    25  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    26  for more details.
    27  
    28  You should have received copies of the GNU General Public License and the
    29  GNU Lesser General Public License along with the GNU MP Library.  If not,
    30  see https://www.gnu.org/licenses/.  */
    31  
    32  #include "gmp.h"
    33  #include "gmp-impl.h"
    34  
    35  #if OPERATION_popcount
    36  #define FNAME mpn_popcount
    37  #define POPHAM(u,v) u
    38  #endif
    39  
    40  #if OPERATION_hamdist
    41  #define FNAME mpn_hamdist
    42  #define POPHAM(u,v) u ^ v
    43  #endif
    44  
    45  mp_bitcnt_t
    46  FNAME (mp_srcptr up,
    47  #if OPERATION_hamdist
    48         mp_srcptr vp,
    49  #endif
    50         mp_size_t n) __GMP_NOTHROW
    51  {
    52    mp_bitcnt_t result = 0;
    53    mp_limb_t p0, p1, p2, p3, x, p01, p23;
    54    mp_size_t i;
    55  
    56    ASSERT (n >= 1);		/* Actually, this code handles any n, but some
    57  				   assembly implementations do not.  */
    58  
    59    for (i = n >> 2; i != 0; i--)
    60      {
    61        p0 = POPHAM (up[0], vp[0]);
    62        p0 -= (p0 >> 1) & MP_LIMB_T_MAX/3;				/* 2 0-2 */
    63        p0 = ((p0 >> 2) & MP_LIMB_T_MAX/5) + (p0 & MP_LIMB_T_MAX/5);	/* 4 0-4 */
    64  
    65        p1 = POPHAM (up[1], vp[1]);
    66        p1 -= (p1 >> 1) & MP_LIMB_T_MAX/3;				/* 2 0-2 */
    67        p1 = ((p1 >> 2) & MP_LIMB_T_MAX/5) + (p1 & MP_LIMB_T_MAX/5);	/* 4 0-4 */
    68  
    69        p01 = p0 + p1;							/* 8 0-8 */
    70        p01 = ((p01 >> 4) & MP_LIMB_T_MAX/17) + (p01 & MP_LIMB_T_MAX/17);	/* 8 0-16 */
    71  
    72        p2 = POPHAM (up[2], vp[2]);
    73        p2 -= (p2 >> 1) & MP_LIMB_T_MAX/3;				/* 2 0-2 */
    74        p2 = ((p2 >> 2) & MP_LIMB_T_MAX/5) + (p2 & MP_LIMB_T_MAX/5);	/* 4 0-4 */
    75  
    76        p3 = POPHAM (up[3], vp[3]);
    77        p3 -= (p3 >> 1) & MP_LIMB_T_MAX/3;				/* 2 0-2 */
    78        p3 = ((p3 >> 2) & MP_LIMB_T_MAX/5) + (p3 & MP_LIMB_T_MAX/5);	/* 4 0-4 */
    79  
    80        p23 = p2 + p3;							/* 8 0-8 */
    81        p23 = ((p23 >> 4) & MP_LIMB_T_MAX/17) + (p23 & MP_LIMB_T_MAX/17);	/* 8 0-16 */
    82  
    83        x = p01 + p23;							/* 8 0-32 */
    84        x = (x >> 8) + x;							/* 8 0-64 */
    85        x = (x >> 16) + x;						/* 8 0-128 */
    86  #if GMP_LIMB_BITS > 32
    87        x = ((x >> 32) & 0xff) + (x & 0xff);				/* 8 0-256 */
    88        result += x;
    89  #else
    90        result += x & 0xff;
    91  #endif
    92        up += 4;
    93  #if OPERATION_hamdist
    94        vp += 4;
    95  #endif
    96      }
    97  
    98    n &= 3;
    99    if (n != 0)
   100      {
   101        x = 0;
   102        do
   103  	{
   104  	  p0 = POPHAM (up[0], vp[0]);
   105  	  p0 -= (p0 >> 1) & MP_LIMB_T_MAX/3;				/* 2 0-2 */
   106  	  p0 = ((p0 >> 2) & MP_LIMB_T_MAX/5) + (p0 & MP_LIMB_T_MAX/5);	/* 4 0-4 */
   107  	  p0 = ((p0 >> 4) + p0) & MP_LIMB_T_MAX/17;			/* 8 0-8 */
   108  
   109  	  x += p0;
   110  	  up += 1;
   111  #if OPERATION_hamdist
   112  	  vp += 1;
   113  #endif
   114  	}
   115        while (--n);
   116  
   117        x = (x >> 8) + x;
   118        x = (x >> 16) + x;
   119  #if GMP_LIMB_BITS > 32
   120        x = (x >> 32) + x;
   121  #endif
   122        result += x & 0xff;
   123      }
   124  
   125    return result;
   126  }