117 lines
3.2 KiB
C
117 lines
3.2 KiB
C
/* mpn_popcount, mpn_hamdist -- mpn bit population count/hamming distance.
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Copyright 1994, 1996, 2000, 2001, 2002, 2005 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP 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 by
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the Free Software Foundation; either version 2.1 of the License, or (at your
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option) any later version.
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The GNU MP 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 GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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MA 02110-1301, USA. */
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#include "gmp.h"
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#include "gmp-impl.h"
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#if OPERATION_popcount
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#define FNAME mpn_popcount
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#define POPHAM(u,v) u
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#endif
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#if OPERATION_hamdist
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#define FNAME mpn_hamdist
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#define POPHAM(u,v) u ^ v
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#endif
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unsigned long
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FNAME (mp_srcptr up,
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#if OPERATION_hamdist
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mp_srcptr vp,
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#endif
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mp_size_t n)
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{
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unsigned long result = 0;
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mp_limb_t p0, p1, p2, p3, x, p01, p23;
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mp_size_t i;
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ASSERT (n >= 1); /* Actually, this code handles any n, but some
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assembly implementations does not. */
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for (i = n >> 2; i != 0; i--)
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{
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p0 = POPHAM (up[0], vp[0]);
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p0 -= (p0 >> 1) & MP_LIMB_T_MAX/3; /* 2 0-2 */
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p0 = ((p0 >> 2) & MP_LIMB_T_MAX/5) + (p0 & MP_LIMB_T_MAX/5); /* 4 0-4 */
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p1 = POPHAM (up[1], vp[1]);
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p1 -= (p1 >> 1) & MP_LIMB_T_MAX/3; /* 2 0-2 */
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p1 = ((p1 >> 2) & MP_LIMB_T_MAX/5) + (p1 & MP_LIMB_T_MAX/5); /* 4 0-4 */
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p01 = p0 + p1; /* 8 0-8 */
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p01 = ((p01 >> 4) & MP_LIMB_T_MAX/17) + (p01 & MP_LIMB_T_MAX/17); /* 8 0-16 */
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p2 = POPHAM (up[2], vp[2]);
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p2 -= (p2 >> 1) & MP_LIMB_T_MAX/3; /* 2 0-2 */
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p2 = ((p2 >> 2) & MP_LIMB_T_MAX/5) + (p2 & MP_LIMB_T_MAX/5); /* 4 0-4 */
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p3 = POPHAM (up[3], vp[3]);
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p3 -= (p3 >> 1) & MP_LIMB_T_MAX/3; /* 2 0-2 */
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p3 = ((p3 >> 2) & MP_LIMB_T_MAX/5) + (p3 & MP_LIMB_T_MAX/5); /* 4 0-4 */
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p23 = p2 + p3; /* 8 0-8 */
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p23 = ((p23 >> 4) & MP_LIMB_T_MAX/17) + (p23 & MP_LIMB_T_MAX/17); /* 8 0-16 */
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x = p01 + p23; /* 8 0-32 */
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x = (x >> 8) + x; /* 8 0-64 */
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x = (x >> 16) + x; /* 8 0-128 */
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#if GMP_LIMB_BITS > 32
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x = ((x >> 32) & 0xff) + (x & 0xff); /* 8 0-256 */
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result += x;
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#else
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result += x & 0xff;
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#endif
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up += 4;
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#if OPERATION_hamdist
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vp += 4;
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#endif
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}
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n &= 3;
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if (n != 0)
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{
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x = 0;
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do
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{
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p0 = POPHAM (up[0], vp[0]);
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p0 -= (p0 >> 1) & MP_LIMB_T_MAX/3; /* 2 0-2 */
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p0 = ((p0 >> 2) & MP_LIMB_T_MAX/5) + (p0 & MP_LIMB_T_MAX/5); /* 4 0-4 */
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p0 = ((p0 >> 4) + p0) & MP_LIMB_T_MAX/17; /* 8 0-8 */
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x += p0;
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up += 1;
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#if OPERATION_hamdist
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vp += 1;
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#endif
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}
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while (--n);
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x = (x >> 8) + x;
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x = (x >> 16) + x;
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#if GMP_LIMB_BITS > 32
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x = (x >> 32) + x;
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#endif
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result += x & 0xff;
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}
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return result;
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}
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