use cutNode as TT cutoff condition #5670
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At low enough depths, fail high with TT only when expected cutnode. Passed STC: https://tests.stockfishchess.org/tests/view/6726357b86d5ee47d953da8c LLR: 2.93 (-2.94,2.94) <0.00,2.00> Total: 41184 W: 10873 L: 10551 D: 19760 Ptnml(0-2): 131, 4728, 10554, 5046, 133 Passed LTC: https://tests.stockfishchess.org/tests/view/6727326a86d5ee47d953db30 LLR: 2.94 (-2.94,2.94) <0.50,2.50> Total: 270888 W: 69040 L: 68243 D: 133605 Ptnml(0-2): 180, 29385, 75485, 30246, 148 Bench: 1362971
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clang-format 18 needs to be run on this PR. (execution 11711483233 / attempt 1) |
ruidazeng
reviewed
Nov 9, 2024
| @@ -635,7 +635,8 @@ Value Search::Worker::search( | |||
| // At non-PV nodes we check for an early TT cutoff | |||
| if (!PvNode && !excludedMove && ttData.depth > depth - (ttData.value <= beta) | |||
| && ttData.value != VALUE_NONE // Can happen when !ttHit or when access race in probe() | |||
| && (ttData.bound & (ttData.value >= beta ? BOUND_LOWER : BOUND_UPPER))) | |||
| && (ttData.bound & (ttData.value >= beta ? BOUND_LOWER : BOUND_UPPER)) | |||
| && (cutNode == (ttData.value >= beta) || depth > 8)) | |||
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where does the OR depth > 8 come from?
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The first implementation I tried didn't have this condition, but also didn't scale to LTC:
STC: https://tests.stockfishchess.org/tests/view/6721521586d5ee47d953d605
failed LTC: https://tests.stockfishchess.org/tests/view/672217ab86d5ee47d953d6c6
This suggested that for higher depths tt values are reliable enough even if cutNode doesn't agree.
Disservin
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At low enough depths, allow TT cutoffs only if
cutNodematches previous TT results.Passed STC:
https://tests.stockfishchess.org/tests/view/6726357b86d5ee47d953da8c
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 41184 W: 10873 L: 10551 D: 19760
Ptnml(0-2): 131, 4728, 10554, 5046, 133
Passed LTC:
https://tests.stockfishchess.org/tests/view/6727326a86d5ee47d953db30
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 270888 W: 69040 L: 68243 D: 133605
Ptnml(0-2): 180, 29385, 75485, 30246, 148
Bench: 1362971