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Introduce Quadruple Extensions

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This patch introduces quadruple extensions, with the new condition of not ttPv. It also generalises all margins, so that extensions can still occur if conditions are only partially fulfilled, but with a stricter margin.

Failed STC:
LLR: -2.94 (-2.94,2.94) <0.00,2.00>
Total: 16096 W: 3984 L: 4228 D: 7884
Ptnml(0-2): 72, 2067, 4002, 1847, 60
https://tests.stockfishchess.org/tests/view/66316422d01fb9ac9bcdbdcd

Passed VVLTC 1:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 96660 W: 24550 L: 24210 D: 47900
Ptnml(0-2): 5, 8776, 30426, 9120, 3
https://tests.stockfishchess.org/tests/view/66361f2c74fa3f41ef2ee091

Passed VVLTC 2:
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 80546 W: 20495 L: 20120 D: 39931
Ptnml(0-2): 6, 7477, 24929, 7858, 3
https://tests.stockfishchess.org/tests/view/66350cf739ba8e443112b3fa

closes https://github.com/official-stockfish/Stockfish/pull/5211

bench 2233743
This commit is contained in:
Viren6 2024-05-04 17:29:23 +01:00 • committed by Joost VandeVondele
parent 351a2e22dd
commit 741aaf8a38
2 changed files with 9 additions and 13 deletions
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21
src/search.cpp
View file

@ -593,7 +593,6 @@ Value Search::Worker::search(
bestMove = Move::none();
(ss + 2)->killers[0] = (ss + 2)->killers[1] = Move::none();
(ss + 2)->cutoffCnt = 0;
ss->multipleExtensions = (ss - 1)->multipleExtensions;
Square prevSq = ((ss - 1)->currentMove).is_ok() ? ((ss - 1)->currentMove).to_sq() : SQ_NONE;
ss->statScore = 0;
@ -1049,17 +1048,16 @@ moves_loop: // When in check, search starts here
if (value < singularBeta)
{
extension = 1;
int doubleMargin = 251 * PvNode - 241 * !ttCapture;
int tripleMargin =
135 + 234 * PvNode - 248 * !ttCapture + 124 * (ss->ttPv || !ttCapture);
int quadMargin = 447 + 354 * PvNode - 300 * !ttCapture + 206 * ss->ttPv;
// We make sure to limit the extensions in some way to avoid a search explosion
if (!PvNode && ss->multipleExtensions <= 16)
{
extension = 2 + (value < singularBeta - 11 && !ttCapture);
depth += depth < 14;
}
if (PvNode && !ttCapture && ss->multipleExtensions <= 5
&& value < singularBeta - 38)
extension = 2;
extension = 1 + (value < singularBeta - doubleMargin)
+ (value < singularBeta - tripleMargin)
+ (value < singularBeta - quadMargin);
depth += ((!PvNode) && (depth < 14));
}
// Multi-cut pruning
@ -1104,7 +1102,6 @@ moves_loop: // When in check, search starts here
// Add extension to new depth
newDepth += extension;
ss->multipleExtensions = (ss - 1)->multipleExtensions + (extension >= 2);
// Speculative prefetch as early as possible
prefetch(tt.first_entry(pos.key_after(move)));

1
src/search.h
View file

@ -74,7 +74,6 @@ struct Stack {
bool inCheck;
bool ttPv;
bool ttHit;
int multipleExtensions;
int cutoffCnt;
};