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Add double bonus for prior countermove fail low

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Add a double extra bonus for particularly bad fail low cases. Original idea by Yoshie2000.

STC: https://tests.stockfishchess.org/tests/view/63a2f0d86b5bf07ac7fad543
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 146488 W: 38992 L: 38532 D: 68964
Ptnml(0-2): 385, 16036, 39965, 16450, 408

LTC: https://tests.stockfishchess.org/tests/view/63a3eaeb6b5bf07ac7fafdec
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 103992 W: 27853 L: 27423 D: 48716
Ptnml(0-2): 41, 10029, 31435, 10441, 50

closes https://github.com/official-stockfish/Stockfish/pull/4302

Bench: 3801857
This commit is contained in:
Muzhen Gaming 2022-12-24 13:05:24 +08:00 • committed by Joost VandeVondele
parent b2bd8699ec
commit 64656f8583
2 changed files with 6 additions and 4 deletions
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1
AUTHORS
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@ -145,6 +145,7 @@ Mira
Miroslav Fontán (Hexik) Miroslav Fontán (Hexik)
Moez Jellouli (MJZ1977) Moez Jellouli (MJZ1977)
Mohammed Li (tthsqe12) Mohammed Li (tthsqe12)
Muzhen J (XInTheDark)
Nathan Rugg (nmrugg) Nathan Rugg (nmrugg)
Nick Pelling (nickpelling) Nick Pelling (nickpelling)
Nicklas Persson (NicklasPersson) Nicklas Persson (NicklasPersson)

9
src/search.cpp
View file

@ -1353,16 +1353,17 @@ moves_loop: // When in check, search starts here
quietsSearched, quietCount, capturesSearched, captureCount, depth); quietsSearched, quietCount, capturesSearched, captureCount, depth);
// Bonus for prior countermove that caused the fail low // Bonus for prior countermove that caused the fail low
else if ( (depth >= 5 || PvNode) else if ( (depth >= 5 || PvNode || bestValue < alpha - 62 * depth)
&& !priorCapture) && !priorCapture)
{ {
//Assign extra bonus if current node is PvNode or cutNode //Assign extra bonus if current node is PvNode or cutNode
//or fail low was really bad //or fail low was really bad
bool extraBonus = PvNode bool extraBonus = PvNode
|| cutNode || cutNode;
|| bestValue < alpha - 62 * depth;
update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * (1 + extraBonus)); bool doubleExtraBonus = extraBonus && bestValue < alpha - 85 * depth;
update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * (1 + extraBonus + doubleExtraBonus));
} }
if (PvNode) if (PvNode)