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Don't copy around DirtyThreats

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The contents of DirtyThreats gets memcpyed twice for each call to do_move.
(Return value optimization doesn't apply to the do_move function itself because
it constructs a std::pair, so it gets copied; and the calls to reset also
require a copy.) This patch inserts the dirty info in place.

Sometimes the caller of do_move ignores the DirtyThreats info, so we pass in
scratch objects. I found that stack-allocating these scratch objects was bad on
Fishtest, so I begrudgingly put them in the Position struct. Both templating
the do_move function on whether dirty threats are needed and putting a
null-check branch for each use of dirty threats were slowdowns locally. Of
course, nothing prevents a future attempt at cleaning this up.

passed STC
LLR: 2.96 (-2.94,2.94) <0.00,2.00>
Total: 68448 W: 17770 L: 17418 D: 33260
Ptnml(0-2): 198, 7425, 18630, 7769, 202
https://tests.stockfishchess.org/tests/view/6914c01a7ca87818523318ba

closes https://github.com/official-stockfish/Stockfish/pull/6414

No functional change
This commit is contained in:
Timothy Herchen
2025-11-13 22:17:03 +01:00
committed by Joost VandeVondele
parent 3ae7684714
commit fa4f05d3ef
5 changed files with 55 additions and 37 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/search.cpp
+4 -4
View File
@@ -531,16 +531,16 @@ void Search::Worker::do_move(
bool capture = pos.capture_stage(move);
nodes.fetch_add(1, std::memory_order_relaxed);
DirtyBoardData dirtyBoardData = pos.do_move(move, st, givesCheck, &tt);
accumulatorStack.push(dirtyBoardData);
auto [dirtyPiece, dirtyThreats] = accumulatorStack.push();
pos.do_move(move, st, givesCheck, dirtyPiece, dirtyThreats, &tt);
if (ss != nullptr)
{
ss->currentMove = move;
ss->continuationHistory =
&continuationHistory[ss->inCheck][capture][dirtyBoardData.dp.pc][move.to_sq()];
&continuationHistory[ss->inCheck][capture][dirtyPiece.pc][move.to_sq()];
ss->continuationCorrectionHistory =
&continuationCorrectionHistory[dirtyBoardData.dp.pc][move.to_sq()];
&continuationCorrectionHistory[dirtyPiece.pc][move.to_sq()];
}
}