Simplify away a term in see pruning

daniel-monroe · vondele · commit 92514fd3a2bf · 2025-07-24T10:32:41.000+02:00
This change only sets the margin to 0 when depth <= 2 and margin <= 42 which never has a difference, thus non-functional Passed non-regression STC LLR: 3.51 (-2.94,2.94) <-1.75,0.25> Total: 306976 W: 78935 L: 78961 D: 149080 Ptnml(0-2): 630, 34097, 84067, 34057, 637 https://tests.stockfishchess.org/tests/view/68708015fa93cf16d3bb2782 closes #6170 No functional change
diff --git a/src/search.cpp b/src/search.cpp
@@ -1047,8 +1047,8 @@ Value Search::Worker::search(
                 }
 
                 // SEE based pruning for captures and checks
-                int seeHist = std::clamp(captHist / 31, -137 * depth, 125 * depth);
-                if (!pos.see_ge(move, -158 * depth - seeHist))
+                int margin = std::clamp(158 * depth + captHist / 31, 0, 283 * depth);
+                if (!pos.see_ge(move, -margin))
                 {
                     bool mayStalemateTrap =
                       depth > 2 && alpha < 0 && pos.non_pawn_material(us) == PieceValue[movedPiece]

Original file line number	Diff line number	Diff line change
`@@ -1047,8 +1047,8 @@ Value Search::Worker::search(`
`1047`	`1047`	`}`
`1048`	`1048`
`1049`	`1049`	`// SEE based pruning for captures and checks`
`1050`		`- int seeHist = std::clamp(captHist / 31, -137 * depth, 125 * depth);`
`1051`		`- if (!pos.see_ge(move, -158 * depth - seeHist))`
	`1050`	`+ int margin = std::clamp(158 * depth + captHist / 31, 0, 283 * depth);`
	`1051`	`+ if (!pos.see_ge(move, -margin))`
`1052`	`1052`	`{`
`1053`	`1053`	`bool mayStalemateTrap =`
`1054`	`1054`	`depth > 2 && alpha < 0 && pos.non_pawn_material(us) == PieceValue[movedPiece]`