diff --git a/cxxmph/cmph_hash_map_test.cc b/cxxmph/cmph_hash_map_test.cc index 73c3290..2ebaa94 100644 --- a/cxxmph/cmph_hash_map_test.cc +++ b/cxxmph/cmph_hash_map_test.cc @@ -14,6 +14,9 @@ int main(int argc, char** argv) { for (int i = 0; i < 2*1000*1000; ++i) { b.insert(make_pair(i, i)); } + for (int i = 0; i < 100*1000*1000; ++i) { + b.find(i); + } /* cmph_hash_map h; h.insert(std::make_pair("-1",-1)); diff --git a/src/MurmurHash2.h b/src/MurmurHash2.h new file mode 100644 index 0000000..52d015a --- /dev/null +++ b/src/MurmurHash2.h @@ -0,0 +1,69 @@ +#ifndef __CXXMPH_MURMUR_HASH2__ +#define __CXXMPH_MURMUR_HASH2__ + +//----------------------------------------------------------------------------- +// MurmurHash2, by Austin Appleby + +// Note - This code makes a few assumptions about how your machine behaves - + +// 1. We can read a 4-byte value from any address without crashing +// 2. sizeof(int) == 4 + +// And it has a few limitations - + +// 1. It will not work incrementally. +// 2. It will not produce the same results on little-endian and big-endian +// machines. + +unsigned int MurmurHash2 ( const void * key, int len, unsigned int seed ) +{ + // 'm' and 'r' are mixing constants generated offline. + // They're not really 'magic', they just happen to work well. + + const unsigned int m = 0x5bd1e995; + const int r = 24; + + // Initialize the hash to a 'random' value + + unsigned int h = seed ^ len; + + // Mix 4 bytes at a time into the hash + + const unsigned char * data = (const unsigned char *)key; + + while(len >= 4) + { + unsigned int k = *(unsigned int *)data; + + k *= m; + k ^= k >> r; + k *= m; + + h *= m; + h ^= k; + + data += 4; + len -= 4; + } + + // Handle the last few bytes of the input array + + switch(len) + { + case 3: h ^= data[2] << 16; + case 2: h ^= data[1] << 8; + case 1: h ^= data[0]; + h *= m; + }; + + // Do a few final mixes of the hash to ensure the last few + // bytes are well-incorporated. + + h ^= h >> 13; + h *= m; + h ^= h >> 15; + + return h; +} + +#endif // __CXXMPH_MURMUR_HASH2__