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Use complexity in search

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This patch uses the complexity measure (from #3875) as a heuristic for null move pruning.
Hopefully, there may be room to use it in other pruning techniques.
I would like to thank vondele and locutus2 for the feedback and suggestions during testing.

Passed STC
LLR: 2.95 (-2.94,2.94) <0.00,2.50>
Total: 35000 W: 9624 L: 9347 D: 16029
Ptnml(0-2): 156, 3894, 9137, 4143, 170
https://tests.stockfishchess.org/tests/view/61dda784c65bf87d6c45ab80

Passed LTC
LLR: 2.94 (-2.94,2.94) <0.50,3.00>
Total: 230776 W: 64227 L: 63454 D: 103095
Ptnml(0-2): 1082, 23100, 66380, 23615, 1211
https://tests.stockfishchess.org/tests/view/61ddd0cf3ddbc32543e72c2b

Closes https://github.com/official-stockfish/Stockfish/pull/3890

Bench: 4464962
This commit is contained in:
Rui Coelho 2022-01-13 18:30:53 +00:00 • committed by Joost VandeVondele
parent c5d45d3220
commit 7678d63cf2
2 changed files with 5 additions and 2 deletions
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1
AUTHORS
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@ -166,6 +166,7 @@ Rodrigo Exterckötter Tjäder
Ron Britvich (Britvich) Ron Britvich (Britvich)
Ronald de Man (syzygy1, syzygy) Ronald de Man (syzygy1, syzygy)
rqs rqs
Rui Coelho (ruicoelhopedro)
Ryan Schmitt Ryan Schmitt
Ryan Takker Ryan Takker
Sami Kiminki (skiminki) Sami Kiminki (skiminki)

6
src/search.cpp
View file

@ -589,7 +589,7 @@ namespace {
bool givesCheck, improving, didLMR, priorCapture; bool givesCheck, improving, didLMR, priorCapture;
bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture; bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture;
Piece movedPiece; Piece movedPiece;
int moveCount, captureCount, quietCount, bestMoveCount, improvement; int moveCount, captureCount, quietCount, bestMoveCount, improvement, complexity;
// Step 1. Initialize node // Step 1. Initialize node
ss->inCheck = pos.checkers(); ss->inCheck = pos.checkers();
@ -760,6 +760,7 @@ namespace {
ss->staticEval = eval = VALUE_NONE; ss->staticEval = eval = VALUE_NONE;
improving = false; improving = false;
improvement = 0; improvement = 0;
complexity = 0;
goto moves_loop; goto moves_loop;
} }
else if (ss->ttHit) else if (ss->ttHit)
@ -803,6 +804,7 @@ namespace {
: 200; : 200;
improving = improvement > 0; improving = improvement > 0;
complexity = abs(ss->staticEval - (us == WHITE ? eg_value(pos.psq_score()) : -eg_value(pos.psq_score())));
// Step 7. Futility pruning: child node (~25 Elo). // Step 7. Futility pruning: child node (~25 Elo).
// The depth condition is important for mate finding. // The depth condition is important for mate finding.
@ -818,7 +820,7 @@ namespace {
&& (ss-1)->statScore < 23767 && (ss-1)->statScore < 23767
&& eval >= beta && eval >= beta
&& eval >= ss->staticEval && eval >= ss->staticEval
&& ss->staticEval >= beta - 20 * depth - improvement / 15 + 204 && ss->staticEval >= beta - 20 * depth - improvement / 15 + 204 + complexity / 25
&& !excludedMove && !excludedMove
&& pos.non_pawn_material(us) && pos.non_pawn_material(us)
&& (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor)) && (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))