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authortoma <toma@283d02a7-25f6-0310-bc7c-ecb5cbfe19da>2009-11-25 17:56:58 +0000
committertoma <toma@283d02a7-25f6-0310-bc7c-ecb5cbfe19da>2009-11-25 17:56:58 +0000
commitc90c389a8a8d9d8661e9772ec4144c5cf2039f23 (patch)
tree6d8391395bce9eaea4ad78958617edb20c6a7573 /kpat/freecell-solver/lookup2.c
downloadtdegames-c90c389a8a8d9d8661e9772ec4144c5cf2039f23.tar.gz
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Copy the KDE 3.5 branch to branches/trinity for new KDE 3.5 features.
BUG:215923 git-svn-id: svn://anonsvn.kde.org/home/kde/branches/trinity/kdegames@1054174 283d02a7-25f6-0310-bc7c-ecb5cbfe19da
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+/*
+--------------------------------------------------------------------
+lookup2.c, by Bob Jenkins, December 1996, Public Domain.
+hash(), hash2(), hash3, and mix() are externally useful functions.
+Routines to test the hash are included if SELF_TEST is defined.
+You can use this free for any purpose. It has no warranty.
+--------------------------------------------------------------------
+
+Note:
+ This code was ripped and modified by Shlomi Fish. The original can
+ be found at http://burtleburtle.net/bob/c/lookup2.c.
+*/
+
+#include <stdio.h>
+#include <stddef.h>
+#include <stdlib.h>
+
+#include "lookup2.h"
+
+
+#define hashsize(n) ((ub4)1<<(n))
+#define hashmask(n) (hashsize(n)-1)
+
+/*
+--------------------------------------------------------------------
+mix -- mix 3 32-bit values reversibly.
+For every delta with one or two bit set, and the deltas of all three
+ high bits or all three low bits, whether the original value of a,b,c
+ is almost all zero or is uniformly distributed,
+* If mix() is run forward or backward, at least 32 bits in a,b,c
+ have at least 1/4 probability of changing.
+* If mix() is run forward, every bit of c will change between 1/3 and
+ 2/3 of the time. (Well, 22/100 and 78/100 for some 2-bit deltas.)
+mix() was built out of 36 single-cycle latency instructions in a
+ structure that could supported 2x parallelism, like so:
+ a -= b;
+ a -= c; x = (c>>13);
+ b -= c; a ^= x;
+ b -= a; x = (a<<8);
+ c -= a; b ^= x;
+ c -= b; x = (b>>13);
+ ...
+ Unfortunately, superscalar Pentiums and Sparcs can't take advantage
+ of that parallelism. They've also turned some of those single-cycle
+ latency instructions into multi-cycle latency instructions. Still,
+ this is the fastest good hash I could find. There were about 2^^68
+ to choose from. I only looked at a billion or so.
+--------------------------------------------------------------------
+*/
+#define mix(a,b,c) \
+{ \
+ a -= b; a -= c; a ^= (c>>13); \
+ b -= c; b -= a; b ^= (a<<8); \
+ c -= a; c -= b; c ^= (b>>13); \
+ a -= b; a -= c; a ^= (c>>12); \
+ b -= c; b -= a; b ^= (a<<16); \
+ c -= a; c -= b; c ^= (b>>5); \
+ a -= b; a -= c; a ^= (c>>3); \
+ b -= c; b -= a; b ^= (a<<10); \
+ c -= a; c -= b; c ^= (b>>15); \
+}
+
+/*
+--------------------------------------------------------------------
+ This works on all machines. hash2() is identical to hash() on
+ little-endian machines, except that the length has to be measured
+ in ub4s instead of bytes. It is much faster than hash(). It
+ requires
+ -- that the key be an array of ub4's, and
+ -- that all your machines have the same endianness, and
+ -- that the length be the number of ub4's in the key
+--------------------------------------------------------------------
+*/
+
+ub4 freecell_solver_lookup2_hash_function(
+ register ub1 *k, /* the key */
+ register ub4 length, /* the length of the key */
+ register ub4 initval /* the previous hash, or an arbitrary value */
+ )
+{
+ register ub4 a,b,c,len;
+
+ /* Set up the internal state */
+ len = length;
+ a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */
+ c = initval; /* the previous hash value */
+
+ /*---------------------------------------- handle most of the key */
+ while (len >= 12)
+ {
+ a += (k[0] +((ub4)k[1]<<8) +((ub4)k[2]<<16) +((ub4)k[3]<<24));
+ b += (k[4] +((ub4)k[5]<<8) +((ub4)k[6]<<16) +((ub4)k[7]<<24));
+ c += (k[8] +((ub4)k[9]<<8) +((ub4)k[10]<<16)+((ub4)k[11]<<24));
+ mix(a,b,c);
+ k += 12; len -= 12;
+ }
+
+ /*------------------------------------- handle the last 11 bytes */
+ c += length;
+ switch(len) /* all the case statements fall through */
+ {
+ case 11: c+=((ub4)k[10]<<24);
+ case 10: c+=((ub4)k[9]<<16);
+ case 9 : c+=((ub4)k[8]<<8);
+ /* the first byte of c is reserved for the length */
+ case 8 : b+=((ub4)k[7]<<24);
+ case 7 : b+=((ub4)k[6]<<16);
+ case 6 : b+=((ub4)k[5]<<8);
+ case 5 : b+=k[4];
+ case 4 : a+=((ub4)k[3]<<24);
+ case 3 : a+=((ub4)k[2]<<16);
+ case 2 : a+=((ub4)k[1]<<8);
+ case 1 : a+=k[0];
+ /* case 0: nothing left to add */
+ }
+ mix(a,b,c);
+ /*-------------------------------------------- report the result */
+ return c;
+}