Adjust history usage in moves loop pruning

Vizvezdenec · vondele · commit f1612612457f · 2024-05-05T13:06:22.000+02:00
After experiments with conthist 5 addition failed really bad divions by 2 passed as a gainer. Passed STC: https://tests.stockfishchess.org/tests/view/6636d7114b68b70d858035ce LLR: 2.94 (-2.94,2.94) <0.00,2.00> Total: 35936 W: 9287 L: 8976 D: 17673 Ptnml(0-2): 81, 4129, 9234, 4446, 78 Passed LTC: https://tests.stockfishchess.org/tests/view/6636ddb64b68b70d858040a8 LLR: 2.95 (-2.94,2.94) <0.50,2.50> Total: 82428 W: 21035 L: 20622 D: 40771 Ptnml(0-2): 29, 8985, 22775, 9394, 31 closes #5217 Bench: 2309253
diff --git a/src/search.cpp b/src/search.cpp
@@ -991,7 +991,7 @@ Value Search::Worker::search(
                 int history =
                   (*contHist[0])[movedPiece][move.to_sq()]
                   + (*contHist[1])[movedPiece][move.to_sq()]
-                  + (*contHist[3])[movedPiece][move.to_sq()]
+                  + (*contHist[3])[movedPiece][move.to_sq()] / 2
                   + thisThread->pawnHistory[pawn_structure_index(pos)][movedPiece][move.to_sq()];
 
                 // Continuation history based pruning (~2 Elo)
