Fixed null move check state bug.

Author: Timmoth

.github/workflows/release-pipeline.yaml

@@ -25,7 +25,7 @@ jobs:
         working-directory: Sapling
         id: get_version
         run: |
-          VERSION=1.0.0
+          VERSION=1.0.1
           echo "Application version: $VERSION"
           echo "::set-output name=version::$VERSION"
 

Sapling.Engine/BoardStateExtensions.cs

@@ -139,6 +139,8 @@ public static BoardState CreateBoardFromArray(Piece[] pieces)
         boardState.Evaluator.ShouldWhiteMirrored = boardState.WhiteKingSquare.IsMirroredSide();
         boardState.Evaluator.ShouldBlackMirrored = boardState.BlackKingSquare.IsMirroredSide();
         boardState.Evaluator.FillAccumulators(boardState);
+
+        boardState.UpdateCheckStatus();
         return boardState;
     }
 
@@ -218,6 +220,7 @@ public static BoardState CreateBoardFromFen(string fen)
         boardState.Evaluator.WhiteMirrored = boardState.WhiteKingSquare.IsMirroredSide();
         boardState.Evaluator.BlackMirrored = boardState.BlackKingSquare.IsMirroredSide();
         boardState.Evaluator.FillAccumulators(boardState);
+        boardState.UpdateCheckStatus();
 
         return boardState;
     }
@@ -588,8 +591,14 @@ public static bool PartialApply(this BoardState board, uint m)
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static void UpdateCheckStatus(this BoardState board)
     {
-        board.InCheck = (board.WhiteToMove && board.IsAttackedByBlack(board.WhiteKingSquare)) ||
-                        (!board.WhiteToMove && board.IsAttackedByWhite(board.BlackKingSquare));
+        if (board.WhiteToMove)
+        {
+            board.InCheck = board.IsAttackedByBlack(board.WhiteKingSquare);
+        }
+        else
+        {
+            board.InCheck = board.IsAttackedByWhite(board.BlackKingSquare);
+        }
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -774,11 +783,11 @@ private static void UpdateRepetitions(this BoardState board, uint move)
     public static void PartialUnApply(this BoardState board, uint m,
         ulong oldHash,
         byte oldEnpassant,
-        bool prevWhiteCheck,
+        bool prevInCheck,
         CastleRights prevCastleRights,
         int prevFiftyMoveCounter)
     {
-        board.InCheck = prevWhiteCheck;
+        board.InCheck = prevInCheck;
         board.EnPassantFile = oldEnpassant;
         board.TurnCount--;
         board.WhiteToMove = !board.WhiteToMove;
@@ -982,15 +991,17 @@ public static void ApplyNullMove(this BoardState board)
 
         board.TurnCount++;
         board.WhiteToMove = !board.WhiteToMove;
+        board.InCheck = false;
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public static void UnApplyNullMove(this BoardState board, ulong oldHash, byte oldEnpassant)
+    public static void UnApplyNullMove(this BoardState board, ulong oldHash, byte oldEnpassant, bool oldCheck)
     {
         board.Hash = oldHash;
         board.EnPassantFile = oldEnpassant;
         board.TurnCount--;
         board.WhiteToMove = !board.WhiteToMove;
+        board.InCheck = oldCheck;
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]

Sapling.Engine/Search/NegaMaxSearch.cs

@@ -104,7 +104,7 @@ public unsafe int
                     var nullMoveScore = -NegaMaxSearch(killers, counters, history, depthFromRoot + 1,
                         Math.Max(depth - reduction - 1, 0), -beta,
                         -beta + 1, true, prevMove);
-                    Board.UnApplyNullMove(originalHash, oldEnpassant);
+                    Board.UnApplyNullMove(originalHash, oldEnpassant, inCheck);
 
                     if (nullMoveScore >= beta)
                     {

Sapling.Engine/Search/QuiescenceSearch.cs

@@ -135,6 +135,8 @@ public unsafe int QuiescenceSearch(int depthFromRoot, int alpha, int beta)
                         continue;
                     }
 
+                    Board.UpdateCheckStatus();
+
                     if (!prevInCheck && !Board.InCheck && scores[moveIndex] < Constants.LosingCaptureBias)
                     {
                         //skip playing bad captures when not in check
@@ -145,7 +147,6 @@ public unsafe int QuiescenceSearch(int depthFromRoot, int alpha, int beta)
 
                     hasValidMove = true;
 
-                    Board.UpdateCheckStatus();
                     Board.FinishApply(m, oldEnpassant, prevCastleRights);
 
                     Sse.Prefetch0(_transpositionTable + (Board.Hash & TtMask));