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Use hashing function that takes into account all UniqueID bytes (#2174)

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Philipp Moritz 2018-06-01 23:07:29 -07:00 • committed by Robert Nishihara
parent e1024d84e9
commit d699bfbf10
1 changed files with 49 additions and 5 deletions
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54
src/ray/id.cc
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@ -82,13 +82,57 @@ bool UniqueID::operator==(const UniqueID &rhs) const {
return std::memcmp(data(), rhs.data(), kUniqueIDSize) == 0;
}
size_t UniqueID::hash() const {
size_t result;
// Skip the bytes for the object prefix.
std::memcpy(&result, id_ + (kObjectIdIndexSize / CHAR_BIT), sizeof(size_t));
return result;
// This code is from https://sites.google.com/site/murmurhash/
// and is public domain.
uint64_t MurmurHash64A(const void *key, int len, unsigned int seed) {
const uint64_t m = 0xc6a4a7935bd1e995;
const int r = 47;
uint64_t h = seed ^ (len * m);
const uint64_t *data = reinterpret_cast<const uint64_t *>(key);
const uint64_t *end = data + (len / 8);
while (data != end) {
uint64_t k = *data++;
k *= m;
k ^= k >> r;
k *= m;
h ^= k;
h *= m;
}
const unsigned char *data2 = reinterpret_cast<const unsigned char *>(data);
switch (len & 7) {
case 7:
h ^= uint64_t(data2[6]) << 48;
case 6:
h ^= uint64_t(data2[5]) << 40;
case 5:
h ^= uint64_t(data2[4]) << 32;
case 4:
h ^= uint64_t(data2[3]) << 24;
case 3:
h ^= uint64_t(data2[2]) << 16;
case 2:
h ^= uint64_t(data2[1]) << 8;
case 1:
h ^= uint64_t(data2[0]);
h *= m;
};
h ^= h >> r;
h *= m;
h ^= h >> r;
return h;
}
size_t UniqueID::hash() const { return MurmurHash64A(&id_[0], kUniqueIDSize, 0); }
std::ostream &operator<<(std::ostream &os, const UniqueID &id) {
os << id.hex();
return os;