mirror of
https://github.com/moses-smt/mosesdecoder.git
synced 2024-12-30 23:42:30 +03:00
135 lines
3.1 KiB
C++
135 lines
3.1 KiB
C++
/* Downloaded from http://sites.google.com/site/murmurhash/ which says "All
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* code is released to the public domain. For business purposes, Murmurhash is
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* under the MIT license."
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* This is modified from the original:
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* ULL tag on 0xc6a4a7935bd1e995 so this will compile on 32-bit.
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* length changed to unsigned int.
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* placed in namespace util
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* add MurmurHashNative
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* default option = 0 for seed
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*/
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#include "util/murmur_hash.hh"
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namespace util {
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//-----------------------------------------------------------------------------
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// MurmurHash2, 64-bit versions, by Austin Appleby
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// The same caveats as 32-bit MurmurHash2 apply here - beware of alignment
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// and endian-ness issues if used across multiple platforms.
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// 64-bit hash for 64-bit platforms
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uint64_t MurmurHash64A ( const void * key, std::size_t len, unsigned int seed )
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{
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const uint64_t m = 0xc6a4a7935bd1e995ULL;
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const int r = 47;
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uint64_t h = seed ^ (len * m);
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const uint64_t * data = (const uint64_t *)key;
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const uint64_t * end = data + (len/8);
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while(data != end)
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{
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uint64_t k = *data++;
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k *= m;
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k ^= k >> r;
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k *= m;
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h ^= k;
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h *= m;
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}
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const unsigned char * data2 = (const unsigned char*)data;
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switch(len & 7)
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{
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case 7: h ^= uint64_t(data2[6]) << 48;
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case 6: h ^= uint64_t(data2[5]) << 40;
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case 5: h ^= uint64_t(data2[4]) << 32;
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case 4: h ^= uint64_t(data2[3]) << 24;
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case 3: h ^= uint64_t(data2[2]) << 16;
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case 2: h ^= uint64_t(data2[1]) << 8;
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case 1: h ^= uint64_t(data2[0]);
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h *= m;
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};
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h ^= h >> r;
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h *= m;
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h ^= h >> r;
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return h;
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}
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// 64-bit hash for 32-bit platforms
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uint64_t MurmurHash64B ( const void * key, std::size_t len, unsigned int seed )
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{
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const unsigned int m = 0x5bd1e995;
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const int r = 24;
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unsigned int h1 = seed ^ len;
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unsigned int h2 = 0;
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const unsigned int * data = (const unsigned int *)key;
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while(len >= 8)
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{
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unsigned int k1 = *data++;
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k1 *= m; k1 ^= k1 >> r; k1 *= m;
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h1 *= m; h1 ^= k1;
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len -= 4;
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unsigned int k2 = *data++;
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k2 *= m; k2 ^= k2 >> r; k2 *= m;
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h2 *= m; h2 ^= k2;
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len -= 4;
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}
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if(len >= 4)
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{
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unsigned int k1 = *data++;
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k1 *= m; k1 ^= k1 >> r; k1 *= m;
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h1 *= m; h1 ^= k1;
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len -= 4;
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}
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switch(len)
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{
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case 3: h2 ^= ((unsigned char*)data)[2] << 16;
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case 2: h2 ^= ((unsigned char*)data)[1] << 8;
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case 1: h2 ^= ((unsigned char*)data)[0];
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h2 *= m;
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};
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h1 ^= h2 >> 18; h1 *= m;
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h2 ^= h1 >> 22; h2 *= m;
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h1 ^= h2 >> 17; h1 *= m;
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h2 ^= h1 >> 19; h2 *= m;
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uint64_t h = h1;
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h = (h << 32) | h2;
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return h;
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}
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// Trick to test for 64-bit architecture at compile time.
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namespace {
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template <unsigned L> uint64_t MurmurHashNativeBackend(const void * key, std::size_t len, unsigned int seed) {
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return MurmurHash64A(key, len, seed);
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}
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template <> uint64_t MurmurHashNativeBackend<4>(const void * key, std::size_t len, unsigned int seed) {
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return MurmurHash64B(key, len, seed);
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}
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} // namespace
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uint64_t MurmurHashNative(const void * key, std::size_t len, unsigned int seed) {
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return MurmurHashNativeBackend<sizeof(void*)>(key, len, seed);
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}
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} // namespace util
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