Replace FNV-1a hash by faster and better MurmurHash64A.

Replace FNV-1a hash algorithm by public domain MurmurHash64A, by Austin
Appleby, which is faster and has better hash properties. This is also
the default hash algorithm of GNU C++ Standard Library.

Startup time on a given system (with x86-64-avx2 binaries) reduces from
378ms to 332ms (46ms faster). Hashing of the largest data input (46.1MB)
goes from 44.2ms to 6.2ms, so about 7x faster.

No functional change

closes https://github.com/official-stockfish/Stockfish/pull/6579

Bench: 2570943
This commit is contained in:
Dieter Dobbelaere
2026-02-08 15:22:21 +01:00
committed by Disservin
parent 005f0f9b2a
commit 6b6334ce8e
2 changed files with 40 additions and 8 deletions
+39
View File
@@ -428,6 +428,45 @@ std::ostream& operator<<(std::ostream& os, SyncCout sc) {
void sync_cout_start() { std::cout << IO_LOCK; } void sync_cout_start() { std::cout << IO_LOCK; }
void sync_cout_end() { std::cout << IO_UNLOCK; } void sync_cout_end() { std::cout << IO_UNLOCK; }
// Hash function based on public domain MurmurHash64A, by Austin Appleby.
uint64_t hash_bytes(const char* data, size_t size) {
const uint64_t m = 0xc6a4a7935bd1e995ull;
const int r = 47;
uint64_t h = size * m;
const char* end = data + (size & ~(size_t) 7);
for (const char* p = data; p != end; p += 8)
{
uint64_t k;
std::memcpy(&k, p, sizeof(k));
k *= m;
k ^= k >> r;
k *= m;
h ^= k;
h *= m;
}
if (size & 7)
{
uint64_t k = 0;
for (int i = (size & 7) - 1; i >= 0; i--)
k = (k << 8) | (uint64_t) end[i];
h ^= k;
h *= m;
}
h ^= h >> r;
h *= m;
h ^= h >> r;
return h;
}
// Trampoline helper to avoid moving Logger to misc.h // Trampoline helper to avoid moving Logger to misc.h
void start_logger(const std::string& fname) { Logger::start(fname); } void start_logger(const std::string& fname) { Logger::start(fname); }
+1 -8
View File
@@ -306,14 +306,7 @@ inline uint64_t mul_hi64(uint64_t a, uint64_t b) {
#endif #endif
} }
inline std::uint64_t hash_bytes(const char* data, std::size_t size) { uint64_t hash_bytes(const char*, size_t);
// FNV-1a 64-bit
const char* p = data;
std::uint64_t h = 14695981039346656037ull;
for (std::size_t i = 0; i < size; ++i)
h = (h ^ p[i]) * 1099511628211ull;
return h;
}
template<typename T> template<typename T>
inline std::size_t get_raw_data_hash(const T& value) { inline std::size_t get_raw_data_hash(const T& value) {