74 lines
1.5 KiB
C++
74 lines
1.5 KiB
C++
// Public domain hash functions
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#ifndef NLMISC_WANG_HASH_H
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#define NLMISC_WANG_HASH_H
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#include "types_nl.h"
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namespace NLMISC {
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// http://burtleburtle.net/bob/hash/integer.html
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inline uint32 wangHash(uint32 a)
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{
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a = (a ^ 61) ^ (a >> 16);
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a = a + (a << 3);
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a = a ^ (a >> 4);
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a = a * 0x27d4eb2d;
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a = a ^ (a >> 15);
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return a;
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}
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// http://naml.us/blog/2012/03
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inline uint64 wangHash64(uint64 key)
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{
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key = (~key) + (key << 21); // key = (key << 21) - key - 1;
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key = key ^ (key >> 24);
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key = (key + (key << 3)) + (key << 8); // key * 265
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key = key ^ (key >> 14);
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key = (key + (key << 2)) + (key << 4); // key * 21
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key = key ^ (key >> 28);
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key = key + (key << 31);
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return key;
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}
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// http://naml.us/blog/2012/03 Inverse 64-bit wang hash
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inline uint64 wangHash64Inv(uint64 key)
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{
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uint64 tmp;
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// Invert key = key + (key << 31)
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tmp = key - (key << 31);
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key = key - (tmp << 31);
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// Invert key = key ^ (key >> 28)
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tmp = key^key >> 28;
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key = key^tmp >> 28;
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// Invert key *= 21
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key *= UINT64_CONSTANT(14933078535860113213);
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// Invert key = key ^ (key >> 14)
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tmp = key^key >> 14;
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tmp = key^tmp >> 14;
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tmp = key^tmp >> 14;
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key = key^tmp >> 14;
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// Invert key *= 265
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key *= UINT64_CONSTANT(15244667743933553977);
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// Invert key = key ^ (key >> 24)
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tmp = key^key >> 24;
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key = key^tmp >> 24;
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// Invert key = (~key) + (key << 21)
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tmp = ~key;
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tmp = ~(key - (tmp << 21));
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tmp = ~(key - (tmp << 21));
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key = ~(key - (tmp << 21));
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return key;
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}
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} /* namespace NLMISC */
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#endif // NLMISC_WANG_HASH_H
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