Introduce Fail Low History Bonus

xu-shawn · vondele · commit d275bf964376 · 2024-08-20T21:34:19.000+02:00
When a node fails low, give TT move a small bonus 1/4 of normal value. Passed STC: LLR: 2.95 (-2.94,2.94) <0.00,2.00> Total: 92384 W: 24094 L: 23691 D: 44599 Ptnml(0-2): 323, 10852, 23465, 11203, 349 https://tests.stockfishchess.org/tests/view/66be80794ff211be9d4eed68 Passed LTC: LLR: 2.94 (-2.94,2.94) <0.50,2.50> Total: 114660 W: 29260 L: 28778 D: 56622 Ptnml(0-2): 97, 12506, 31653, 12966, 108 https://tests.stockfishchess.org/tests/view/66bf63ee4ff211be9d4eeef0 closes #5539 bench 1463003
diff --git a/src/search.cpp b/src/search.cpp
@@ -1361,6 +1361,10 @@ Value Search::Worker::search(
               << stat_bonus(depth) * bonus / 25;
     }
 
+    // Bonus when search fails low and there is a TT move
+    else if (moveCount > 1 && ttData.move && (cutNode || PvNode))
+        thisThread->mainHistory[us][ttData.move.from_to()] << stat_bonus(depth) / 4;
+
     if (PvNode)
         bestValue = std::min(bestValue, maxValue);
 

Original file line number	Diff line number	Diff line change
`@@ -1361,6 +1361,10 @@ Value Search::Worker::search(`
`1361`	`1361`	`<< stat_bonus(depth) * bonus / 25;`
`1362`	`1362`	`}`
`1363`	`1363`
	`1364`	`+ // Bonus when search fails low and there is a TT move`
	`1365`	`+ else if (moveCount > 1 && ttData.move && (cutNode \|\| PvNode))`
	`1366`	`+ thisThread->mainHistory[us][ttData.move.from_to()] << stat_bonus(depth) / 4;`
	`1367`	`+`
`1364`	`1368`	`if (PvNode)`
`1365`	`1369`	`bestValue = std::min(bestValue, maxValue);`
`1366`	`1370`