🔍 Add basic (quiet) history malus/penalty

src/Lynx/Search/NegaMax.cs

@@ -182,6 +182,9 @@ private int NegaMax(int depth, int ply, int alpha, int beta, bool parentWasNullM
             }
         }
 
+        Span<Move> visitedMoves = stackalloc Move[pseudoLegalMoves.Length];
+        int visitedMovesCounter = 0;
+
         for (int moveIndex = 0; moveIndex < pseudoLegalMoves.Length; ++moveIndex)
         {
             // Incremental move sorting, inspired by https://github.com/jw1912/Chess-Challenge and suggested by toanth
@@ -205,6 +208,8 @@ private int NegaMax(int depth, int ply, int alpha, int beta, bool parentWasNullM
                 continue;
             }
 
+            visitedMoves[visitedMovesCounter++] = move;
+
             ++_nodes;
             isAnyMoveValid = true;
 
@@ -322,7 +327,7 @@ private int NegaMax(int depth, int ply, int alpha, int beta, bool parentWasNullM
 
                 if (!move.IsCapture())
                 {
-                    // 🔍 History moves
+                    // 🔍 Quiet history moves
                     // Doing this only in beta cutoffs (instead of when eval > alpha) was suggested by Sirius author
                     var piece = move.Piece();
                     var targetSquare = move.TargetSquare();
@@ -331,6 +336,22 @@ private int NegaMax(int depth, int ply, int alpha, int beta, bool parentWasNullM
                         _historyMoves[piece][targetSquare],
                         EvaluationConstants.HistoryBonus[depth]);
 
+                    // 🔍 History penalty/malus
+                    // When a quiet move fails high, penalize previous visited quiet moves
+                    for (int i = 0; i < visitedMovesCounter - 1; ++i)
+                    {
+                        var visitedMove = visitedMoves[i];
+                        if (!visitedMove.IsCapture())
+                        {
+                            var visitedMovePiece = visitedMove.Piece();
+                            var visitedMoveTargetSquare = visitedMove.TargetSquare();
+
+                            _historyMoves[visitedMovePiece][visitedMoveTargetSquare] = ScoreHistoryMove(
+                                _historyMoves[visitedMovePiece][visitedMoveTargetSquare],
+                                -EvaluationConstants.HistoryBonus[depth]);
+                        }
+                    }
+
                     // 🔍 Killer moves
                     if (move.PromotedPiece() == default && move != _killerMoves[0][ply])
                     {