Tweak usage of correction history

Instead of using linear formula use quadratic one. Maximum impact of correction history is doubled this way, it breaks even with previous formula on half of maximum value. Passed STC: https://tests.stockfishchess.org/tests/view/659591e579aa8af82b95d7e8 LLR: 2.93 (-2.94,2.94) <0.00,2.00> Total: 225216 W: 57616 L: 57019 D: 110581 Ptnml(0-2): 747, 26677, 57201, 27198, 785 Passed LTC: https://tests.stockfishchess.org/tests/view/6596ee0b79aa8af82b95f08a LLR: 2.94 (-2.94,2.94) <0.50,2.50> Total: 73314 W: 18524 L: 18125 D: 36665 Ptnml(0-2): 41, 8159, 19875, 8524, 58 closes #4967 Bench: 1464785
official-stockfish · Jan 7, 2024 · 6f9071c · 6f9071c
1 parent a5f7386
commit 6f9071c
Showing 1 changed file with 14 additions and 4 deletions.
diff --git a/src/search.cpp b/src/search.cpp
@@ -745,7 +745,9 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
 
         Value newEval =
           ss->staticEval
-          + thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)] / 32;
+          + thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)]
+              * std::abs(thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)])
+              / 16384;
 
         ss->staticEval = eval = to_static_eval(newEval);
 
@@ -759,7 +761,9 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
 
         Value newEval =
           ss->staticEval
-          + thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)] / 32;
+          + thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)]
+              * std::abs(thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)])
+              / 16384;
 
         ss->staticEval = eval = to_static_eval(newEval);
 
@@ -1502,7 +1506,10 @@ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
 
             Value newEval =
               ss->staticEval
-              + thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)] / 32;
+              + thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)]
+                  * std::abs(
+                    thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)])
+                  / 16384;
 
             ss->staticEval = bestValue = to_static_eval(newEval);
 
@@ -1519,7 +1526,10 @@ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
 
             Value newEval =
               ss->staticEval
-              + thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)] / 32;
+              + thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)]
+                  * std::abs(
+                    thisThread->correctionHistory[us][pawn_structure_index<Correction>(pos)])
+                  / 16384;
 
             ss->staticEval = bestValue = to_static_eval(newEval);
         }