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Increase the maximum hash size by a factor of 256

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Conceptually group hash clusters into super clusters of 256 clusters.
This scheme allows us to use hash sizes up to 32 TB
(= 2^32 super clusters = 2^40 clusters).

Use 48 bits of the Zobrist key to choose the cluster index. We use 8
extra bits to mitigate the quantization error for very large hashes when
scaling the hash key to cluster index.

The hash index computation is organized to be compatible with the existing
scheme for power-of-two hash sizes up to 128 GB.

Fixes https://github.com/official-stockfish/Stockfish/issues/1349

closes https://github.com/official-stockfish/Stockfish/pull/2722

Passed non-regression STC:
LLR: 2.93 (-2.94,2.94) {-1.50,0.50}
Total: 37976 W: 7336 L: 7211 D: 23429
Ptnml(0-2): 578, 4295, 9149, 4356, 610
https://tests.stockfishchess.org/tests/view/5edcbaaef29b40b0fc95abc5

No functional change.
This commit is contained in:
Sami Kiminki
2020-06-05 20:17:00 +03:00
committed by Joost VandeVondele
parent b081e52239
commit 4b10578acb
3 changed files with 18 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
src/tt.cpp
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@@ -65,8 +65,10 @@ void TranspositionTable::resize(size_t mbSize) {
aligned_ttmem_free(mem);
clusterCount = mbSize * 1024 * 1024 / sizeof(Cluster);
table = static_cast<Cluster*>(aligned_ttmem_alloc(clusterCount * sizeof(Cluster), mem));
superClusterCount = mbSize * 1024 * 1024 / (sizeof(Cluster) * ClustersPerSuperCluster);
table = static_cast<Cluster*>(
aligned_ttmem_alloc(superClusterCount * ClustersPerSuperCluster * sizeof(Cluster), mem));
if (!mem)
{
std::cerr << "Failed to allocate " << mbSize
@@ -89,6 +91,8 @@ void TranspositionTable::clear() {
{
threads.emplace_back([this, idx]() {
const size_t clusterCount = superClusterCount * ClustersPerSuperCluster;
// Thread binding gives faster search on systems with a first-touch policy
if (Options["Threads"] > 8)
WinProcGroup::bindThisThread(idx);