prior countermove bonus for capture that caused fail low

bench 914094
official-stockfish · Nov 23, 2024 · f7157b0 · f7157b0
1 parent 82b092c
commit f7157b0
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Showing 2 changed files with 16 additions and 5 deletions.
diff --git a/src/search.cpp b/src/search.cpp
@@ -889,7 +889,8 @@ Value Search::Worker::search(
             // Prefetch the TT entry for the resulting position
             prefetch(tt.first_entry(pos.key_after(move)));
 
-            ss->currentMove = move;
+            ss->currentMove   = move;
+            ss->capturedPiece = captured;
             ss->continuationHistory =
               &this->continuationHistory[ss->inCheck][true][pos.moved_piece(move)][move.to_sq()];
             ss->continuationCorrectionHistory =
@@ -1139,7 +1140,8 @@ Value Search::Worker::search(
         prefetch(tt.first_entry(pos.key_after(move)));
 
         // Update the current move (this must be done after singular extension search)
-        ss->currentMove = move;
+        ss->currentMove   = move;
+        ss->capturedPiece = pos.piece_on(move.to_sq());
         ss->continuationHistory =
           &thisThread->continuationHistory[ss->inCheck][capture][movedPiece][move.to_sq()];
         ss->continuationCorrectionHistory =
@@ -1403,6 +1405,13 @@ Value Search::Worker::search(
               << stat_bonus(depth) * bonus / 24;
     }
 
+    else if (priorCapture && prevSq != SQ_NONE)
+    {
+        // bonus for prior countermoves that caused the fail low
+        Piece capturedPiece = (ss - 1)->capturedPiece;
+        thisThread->captureHistory[pos.piece_on(prevSq)][prevSq][type_of(capturedPiece)]
+          << stat_bonus(depth) * 2;
+    }
     // Bonus when search fails low and there is a TT move
     else if (ttData.move && !allNode)
         thisThread->mainHistory[us][ttData.move.from_to()] << stat_bonus(depth) * 23 / 100;
@@ -1647,7 +1656,8 @@ Value Search::Worker::qsearch(Position& pos, Stack* ss, Value alpha, Value beta)
         prefetch(tt.first_entry(pos.key_after(move)));
 
         // Update the current move
-        ss->currentMove = move;
+        ss->currentMove   = move;
+        ss->capturedPiece = pos.piece_on(move.to_sq());
         ss->continuationHistory =
           &thisThread
              ->continuationHistory[ss->inCheck][capture][pos.moved_piece(move)][move.to_sq()];
@@ -2167,4 +2177,4 @@ bool RootMove::extract_ponder_from_tt(const TranspositionTable& tt, Position& po
 }
 
 
-}  // namespace Stockfish
+}  // namespace Stockfish
diff --git a/src/search.h b/src/search.h
@@ -66,6 +66,7 @@ struct Stack {
     CorrectionHistory<PieceTo>* continuationCorrectionHistory;
     int                         ply;
     Move                        currentMove;
+    Piece                       capturedPiece;
     Move                        excludedMove;
     Value                       staticEval;
     int                         statScore;
@@ -356,4 +357,4 @@ class Worker {
 
 }  // namespace Stockfish
 
-#endif  // #ifndef SEARCH_H_INCLUDED
+#endif  // #ifndef SEARCH_H_INCLUDED