jirayu_sri/stockfish
1
0
Fork 0
mirror of https://github.com/official-stockfish/Stockfish.git synced 2026-07-23 05:07:14 +00:00
Code Issues Packages Projects Releases Wiki Activity

prefetch the TT entry as soon as the move is known

Browse Source 
Worker::do_move computes the successor hash key via the new
Position::key_after(m) and prefetches the TT entry one full do_move
earlier than the existing prefetch in Position::do_move. key_after does
not model castling, en passant or promotion keys exactly; for rare
moves the prefetch lands on an unused line.

`key_after` has been around since 2014 (https://github.com/official-stockfish/Stockfish/commit/82d065b0) and was removed in (https://github.com/official-stockfish/Stockfish/pull/5770). Adding back `prefetch_key` helps in common, normal moves at the cost of extra compute.

Speedup (PGO vs PGO, interleaved paired bench, n=48 pairs, Apple M2
Pro / apple-silicon): +0.69% [0.47, 0.91]

Passed STC:
https://tests.stockfishchess.org/tests/view/6a291f8d7c758d82accea17f
LLR: 4.24 (-2.94,2.94) <0.00,2.00>
Total: 473504 W: 121250 L: 120228 D: 232026
Ptnml(0-2): 1112, 51137, 131251, 52121, 1131

No functional change

closes https://github.com/official-stockfish/Stockfish/pull/6911

No functional change
This commit is contained in:
Dalton Hanaway
2026-06-25 13:03:44 +02:00
committed by Joost VandeVondele
parent 31e89adf70
commit 6f97594eda
4 changed files with 25 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/search.cpp
+4
View File
@@ -634,6 +634,10 @@ void Search::Worker::do_move(Position& pos, const Move move, StateInfo& st, Stac
void Search::Worker::do_move(
Position& pos, const Move move, StateInfo& st, const bool givesCheck, Stack* const ss) {
// prefetch_key does not model castling, en passant or promotion keys
// exactly; for rare moves the prefetch lands on an unused line.
prefetch(tt.first_entry(pos.prefetch_key(move)));
bool capture = pos.capture_stage(move);
++nodes;