Tweak static eval history update

locutus2 · Disservin · commit 3cfaef74311e · 2023-12-31T20:09:09.000+01:00
Modify the applied static eval bonus for main and pawn history with different factors for positive and negative values. Passed STC: https://tests.stockfishchess.org/tests/view/659132e179aa8af82b957bb0 LLR: 2.93 (-2.94,2.94) <0.00,2.00> Total: 12512 W: 3308 L: 3027 D: 6177 Ptnml(0-2): 32, 1372, 3189, 1609, 54 Passed LTC: https://tests.stockfishchess.org/tests/view/65913e3d79aa8af82b957cd2 LLR: 2.94 (-2.94,2.94) <0.50,2.50> Total: 35946 W: 9128 L: 8809 D: 18009 Ptnml(0-2): 19, 3879, 9862, 4190, 23 closes #4952 Bench: 1392883
diff --git a/src/search.cpp b/src/search.cpp
@@ -772,6 +772,7 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
     if (is_ok((ss - 1)->currentMove) && !(ss - 1)->inCheck && !priorCapture)
     {
         int bonus = std::clamp(-13 * int((ss - 1)->staticEval + ss->staticEval), -1652, 1546);
+        bonus     = bonus > 0 ? 2 * bonus : bonus / 2;
         thisThread->mainHistory[~us][from_to((ss - 1)->currentMove)] << bonus;
         if (type_of(pos.piece_on(prevSq)) != PAWN && type_of((ss - 1)->currentMove) != PROMOTION)
             thisThread->pawnHistory[pawn_structure_index(pos)][pos.piece_on(prevSq)][prevSq]

Original file line number	Diff line number	Diff line change
`@@ -772,6 +772,7 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo`
`772`	`772`	`if (is_ok((ss - 1)->currentMove) && !(ss - 1)->inCheck && !priorCapture)`
`773`	`773`	`{`
`774`	`774`	`int bonus = std::clamp(-13 * int((ss - 1)->staticEval + ss->staticEval), -1652, 1546);`
	`775`	`+ bonus = bonus > 0 ? 2 * bonus : bonus / 2;`
`775`	`776`	`thisThread->mainHistory[~us][from_to((ss - 1)->currentMove)] << bonus;`
`776`	`777`	`if (type_of(pos.piece_on(prevSq)) != PAWN && type_of((ss - 1)->currentMove) != PROMOTION)`
`777`	`778`	`thisThread->pawnHistory[pawn_structure_index(pos)][pos.piece_on(prevSq)][prevSq]`