Adjust probcut on staticEval

tsoj · vondele · commit 7a07ac0e768a · 2025-08-09T09:08:38.000+02:00
Reducing probcut depth more when staticEval is very good and less if staticEval is not so good compared to beta STC: https://tests.stockfishchess.org/tests/view/68926bf6690844f940fa1350 LLR: 2.98 (-2.94,2.94) <0.00,2.00> Total: 174400 W: 45698 L: 45174 D: 83528 Ptnml(0-2): 622, 20356, 44672, 20976, 574 LTC: https://tests.stockfishchess.org/tests/view/689651b4f8a258623dda6531 LLR: 2.95 (-2.94,2.94) <0.50,2.50> Total: 56010 W: 14547 L: 14191 D: 27272 Ptnml(0-2): 31, 5929, 15738, 6267, 40 This patch was generated using qwen3-235b-a22b-thinking-2507: Prompt: https://rentry.co/bm6vriai Thinking: https://rentry.co/34km4zf8 Final respone: https://rentry.co/rauotrvr closes official-stockfish#6219 Bench: 3629755
diff --git a/src/search.cpp b/src/search.cpp
@@ -914,7 +914,8 @@ Value Search::Worker::search(
         assert(probCutBeta < VALUE_INFINITE && probCutBeta > beta);
 
         MovePicker mp(pos, ttData.move, probCutBeta - ss->staticEval, &captureHistory);
-        Depth      probCutDepth = std::max(depth - 5, 0);
+        Depth      dynamicReduction = (ss->staticEval - beta) / 300;
+        Depth      probCutDepth     = std::max(depth - 5 - dynamicReduction, 0);
 
         while ((move = mp.next_move()) != Move::none())
         {

Original file line number	Diff line number	Diff line change
`@@ -914,7 +914,8 @@ Value Search::Worker::search(`
`914`	`914`	`assert(probCutBeta < VALUE_INFINITE && probCutBeta > beta);`
`915`	`915`
`916`	`916`	`MovePicker mp(pos, ttData.move, probCutBeta - ss->staticEval, &captureHistory);`
`917`		`- Depth probCutDepth = std::max(depth - 5, 0);`
	`917`	`+ Depth dynamicReduction = (ss->staticEval - beta) / 300;`
	`918`	`+ Depth probCutDepth = std::max(depth - 5 - dynamicReduction, 0);`
`918`	`919`
`919`	`920`	`while ((move = mp.next_move()) != Move::none())`
`920`	`921`	`{`