Fix bug in repetition detection
This commit is contained in:
Sebastian Lague
parent
4438d69e7e
commit
a6c102ba30
4 changed files with 313 additions and 20 deletions
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@ -10,16 +10,17 @@ namespace ChessChallenge.API
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{
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readonly Chess.Board board;
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readonly APIMoveGen moveGen;
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readonly RepetitionTable repetitionTable;
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readonly HashSet<ulong> repetitionHistory;
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readonly PieceList[] allPieceLists;
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readonly PieceList[] validPieceLists;
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readonly Move[] movesDest;
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Move[] cachedLegalMoves;
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bool hasCachedMoves;
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Move[] cachedLegalCaptureMoves;
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bool hasCachedCaptureMoves;
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readonly Move[] movesDest;
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int depth;
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/// <summary>
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/// Create a new board. Note: this should not be used in the challenge,
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@ -31,6 +32,7 @@ namespace ChessChallenge.API
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board = new Chess.Board();
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board.LoadPosition(boardSource.StartPositionInfo);
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GameMoveHistory = new Move[boardSource.AllGameMoves.Count];
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repetitionTable = new();
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for (int i = 0; i < boardSource.AllGameMoves.Count; i ++)
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{
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@ -61,9 +63,8 @@ namespace ChessChallenge.API
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this.validPieceLists = validPieceLists.ToArray();
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// Init rep history
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repetitionHistory = new HashSet<ulong>(board.RepetitionPositionHistory);
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GameRepetitionHistory = repetitionHistory.ToArray();
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repetitionHistory.Remove(board.ZobristKey);
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GameRepetitionHistory = board.RepetitionPositionHistory.ToArray();
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repetitionTable.Init(board);
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}
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/// <summary>
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@ -75,9 +76,11 @@ namespace ChessChallenge.API
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{
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if (!move.IsNull)
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{
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repetitionHistory.Add(board.ZobristKey);
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OnPositionChanged();
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board.MakeMove(new Chess.Move(move.RawValue), inSearch: true);
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repetitionTable.Push(ZobristKey, move.IsCapture || move.MovePieceType == PieceType.Pawn);
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depth++;
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}
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}
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@ -88,9 +91,9 @@ namespace ChessChallenge.API
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{
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if (!move.IsNull)
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{
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repetitionTable.TryPop();
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board.UndoMove(new Chess.Move(move.RawValue), inSearch: true);
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OnPositionChanged();
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repetitionHistory.Remove(board.ZobristKey);
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}
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}
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@ -209,7 +212,7 @@ namespace ChessChallenge.API
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/// This includes both positions in the actual game, and positions reached by
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/// making moves while the bot is thinking.
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/// </summary>
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public bool IsRepeatedPosition() => repetitionHistory.Contains(board.ZobristKey);
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public bool IsRepeatedPosition() => depth > 0 && repetitionTable.Contains(board.ZobristKey);
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/// <summary>
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/// Test if there are sufficient pieces remaining on the board to potentially deliver checkmate.
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@ -18,9 +18,13 @@ namespace ChessChallenge.Application
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{
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anyFailed = false;
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new SearchTest2().Run();
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RepetitionTest();
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DrawTest();
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MoveGenTest();
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PieceListTest();
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DrawTest();
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CheckTest();
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MiscTest();
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TestBitboards();
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@ -225,6 +229,118 @@ namespace ChessChallenge.Application
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}
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static void RepetitionTest()
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{
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Console.WriteLine("Repetition test");
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string fen = "3k4/8/3K4/8/8/8/8/4Q3 w - - 0 1";
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var board = new Chess.Board();
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board.LoadPosition(fen);
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boardAPI = new(board);
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// -- Simple repeated position in search --
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string[] moveStrings = { "d6c6", "d8c8", "c6d6", "c8d8" };
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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Make(moveStrings[0]); // Kc6
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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Make(moveStrings[1]); // ... Kc8
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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Make(moveStrings[2]); // Kd6
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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var move = Make(moveStrings[3]); // ...Kd8 (repeated position)
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Assert(boardAPI.IsRepeatedPosition(), "should be repetition");
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boardAPI.UndoMove(move); // Undo ...Kd8 (no longer repeated position)
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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// -- Repetition of position in actual game occuring in search --
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board.LoadPosition(fen);
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board.MakeMove(MoveUtility.GetMoveFromUCIName("e1e2", board), inSearch: false); // Qe2
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board.MakeMove(MoveUtility.GetMoveFromUCIName("d8c8", board), inSearch: false); // ...Kc8
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board.MakeMove(MoveUtility.GetMoveFromUCIName("d6c6", board), inSearch: false); // Kc6
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board.MakeMove(MoveUtility.GetMoveFromUCIName("c8d8", board), inSearch: false); // ...Kd8
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boardAPI = new(board);
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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var moveKd6 = Make("c6d6"); // Kd6 (repetition of position in game)
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Assert(boardAPI.IsRepeatedPosition(), "Should be repetition");
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boardAPI.UndoMove(moveKd6); // Undo Kd6
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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boardAPI.MakeMove(moveKd6); // Redo Kd6
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Assert(boardAPI.IsRepeatedPosition(), "Should be repetition");
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var moveKc8 = Make("d8c8"); // ...Kc8
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boardAPI.UndoMove(moveKc8);
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boardAPI.UndoMove(moveKd6);
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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boardAPI.MakeMove(moveKd6);
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Assert(boardAPI.IsRepeatedPosition(), "Should be repetition");
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// -- Same test but purely in search --
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board.LoadPosition(fen);
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boardAPI = new(board);
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Make("e1e2"); // Qe2
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Make("d8c8"); // ...Kc8
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Make("d6c6"); // Kc6
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Make("c8d8"); // ...Kd8
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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moveKd6 = Make("c6d6"); // Kd6 (repetition of position in game)
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Assert(boardAPI.IsRepeatedPosition(), "Should be repetition");
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boardAPI.UndoMove(moveKd6); // Undo Kd6
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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boardAPI.MakeMove(moveKd6); // Redo Kd6
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Assert(boardAPI.IsRepeatedPosition(), "Should be repetition");
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moveKc8 = Make("d8c8"); // ...Kc8
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boardAPI.UndoMove(moveKc8);
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boardAPI.UndoMove(moveKd6);
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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boardAPI.MakeMove(moveKd6);
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Assert(boardAPI.IsRepeatedPosition(), "Should be repetition");
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// Another test
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board.LoadPosition("k7/1p6/2pp4/1QQ5/1b3N2/8/1qq1PPPP/3q2BK w - - 0 1");
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boardAPI = new(board);
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Make("b5a5");
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Make("b4a5");
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Make("c5a5");
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Make("a8b8");
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Make("a5d8");
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Make("b8a7");
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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Make("d8a5");
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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Make("a7b8");
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Assert(boardAPI.IsRepeatedPosition(), "Should be repetition");
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Make("a5d8");
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Assert(boardAPI.IsRepeatedPosition(), "Should be repetition");
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Make("b8a7");
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Assert(boardAPI.IsRepeatedPosition(), "Should be repetition");
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var pawnMove = Make("h2h4");
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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boardAPI.UndoMove(pawnMove);
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Assert(boardAPI.IsRepeatedPosition(), "Should be repetition");
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boardAPI.MakeMove(pawnMove);
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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Make("d1c1");
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Make("d8a5");
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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Make("a7b8");
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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Make("a5d8");
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Assert(!boardAPI.IsRepeatedPosition(), "Should not be repetition");
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Make("b8a7");
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Assert(boardAPI.IsRepeatedPosition(), "Should be repetition");
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Make("d8a5");
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Assert(boardAPI.IsRepeatedPosition(), "Should be repetition");
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API.Move Make(string name)
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{
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var move = new API.Move(name, boardAPI);
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boardAPI.MakeMove(move);
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return move;
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}
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}
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static void DrawTest()
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{
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Console.WriteLine("Draw test");
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@ -457,7 +573,7 @@ namespace ChessChallenge.Application
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ulong RecreateOpponentAttackMap()
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{
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ulong bb = 0;
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for (int i = 0; i < 64; i ++)
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for (int i = 0; i < 64; i++)
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{
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if (boardAPI.SquareIsAttackedByOpponent(new Square(i)))
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{
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@ -538,6 +654,117 @@ namespace ChessChallenge.Application
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Console.ResetColor();
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}
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public class SearchTest2
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{
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API.Board board;
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int numSkips;
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int numCalls;
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int numMates;
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int numDraws;
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int numExtend;
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public void Run()
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{
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Console.WriteLine("Running misc search test");
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Chess.Board b = new();
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b.LoadPosition("8/2b5/2kp4/2p2K2/7P/1p3RP1/2n3N1/8 w - - 0 1");
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board = new API.Board(b);
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var sw = System.Diagnostics.Stopwatch.StartNew();
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Search(7, -10000, 10000);
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sw.Stop();
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Console.WriteLine("Time: " + sw.ElapsedMilliseconds + " ms");
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long testVal = numCalls + numSkips + numMates + numDraws;
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//17092086 skip: 3740 mate: 31 draw: 3803 extend: 172125
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//Console.WriteLine(numCalls + " skip: " + numSkips + " mate: " + numMates + " draw: " + numDraws + " extend: " + numExtend);
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Console.WriteLine(testVal);
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bool passed = testVal == 17092086;
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//Assert(passed, "Test failed");
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anyFailed &= passed;
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}
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int Search(int plyRemaining, int alpha, int beta, bool isQ = false)
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{
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numCalls++;
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if (!isQ)
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{
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if (plyRemaining == 0)
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{
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return Search(-1, alpha, beta, true);
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}
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if (board.IsInCheckmate())
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{
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numMates++;
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return -10000;
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}
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if (board.IsDraw())
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{
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numDraws++;
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return 0;
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}
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if ((numCalls % 4 == 0 || numCalls % 9 == 0) && plyRemaining > 2)
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{
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if (board.TrySkipTurn())
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{
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numSkips++;
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Search(plyRemaining - 2, -beta, -alpha);
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board.UndoSkipTurn();
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}
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}
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}
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API.Move[] moves;
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if (numCalls % 3 == 0 || numCalls % 7 == 0)
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{
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Span<API.Move> moveSpan = stackalloc API.Move[256];
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board.GetLegalMovesNonAlloc(ref moveSpan, isQ);
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// (don't actually care about allocations here, just testing the func)
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moves = moveSpan.ToArray();
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}
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else
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{
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moves = board.GetLegalMoves(isQ);
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}
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if (isQ && moves.Length == 0)
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{
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int numWhite = BitboardHelper.GetNumberOfSetBits(board.WhitePiecesBitboard);
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int numBlack = BitboardHelper.GetNumberOfSetBits(board.BlackPiecesBitboard);
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int e = numWhite - numBlack;
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return e * (board.IsWhiteToMove ? 1 : -1);
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}
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int best = int.MinValue;
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foreach (var move in moves)
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{
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board.MakeMove(move);
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int extend = !isQ && board.IsInCheck() ? 1 : 0;
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numExtend += extend;
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int eval = -Search(plyRemaining - 1 + extend, -beta, -alpha, isQ);
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best = Math.Max(best, eval);
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board.UndoMove(move);
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if (eval >= beta)
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{
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return eval;
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}
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if (eval > alpha)
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{
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alpha = eval;
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}
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}
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return best;
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}
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}
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public class SearchTest
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{
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API.Board board;
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@ -620,4 +847,3 @@ namespace ChessChallenge.Application
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}
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}
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@ -54,6 +54,7 @@ namespace ChessChallenge.Chess
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// List of (hashed) positions since last pawn move or capture (for detecting 3-fold repetition)
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public Stack<ulong> RepetitionPositionHistory;
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public Stack<string> RepetitionPositionHistoryFen;
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Stack<GameState> gameStateHistory;
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public GameState currentGameState;
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@ -269,6 +270,7 @@ namespace ChessChallenge.Chess
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if (!inSearch)
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{
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RepetitionPositionHistory.Clear();
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RepetitionPositionHistoryFen.Clear();
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}
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newFiftyMoveCounter = 0;
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}
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@ -281,6 +283,7 @@ namespace ChessChallenge.Chess
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if (!inSearch)
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{
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RepetitionPositionHistory.Push(newState.zobristKey);
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RepetitionPositionHistoryFen.Push(FenUtility.CurrentFen(this));
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AllGameMoves.Add(move);
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}
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}
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@ -372,6 +375,7 @@ namespace ChessChallenge.Chess
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if (!inSearch && RepetitionPositionHistory.Count > 0)
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{
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RepetitionPositionHistory.Pop();
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RepetitionPositionHistoryFen.Pop();
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}
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if (!inSearch)
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{
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@ -522,6 +526,7 @@ namespace ChessChallenge.Chess
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RepetitionPositionHistory.Push(zobristKey);
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gameStateHistory.Push(currentGameState);
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RepetitionPositionHistoryFen.Push(FenUtility.CurrentFen(this));
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}
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void UpdateSliderBitboards()
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@ -546,6 +551,7 @@ namespace ChessChallenge.Chess
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KingSquare = new int[2];
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RepetitionPositionHistory = new Stack<ulong>(capacity: 64);
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RepetitionPositionHistoryFen = new Stack<string>(capacity: 64);
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gameStateHistory = new Stack<GameState>(capacity: 64);
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currentGameState = new GameState();
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58
Chess-Challenge/src/Framework/Chess/Board/RepetitionTable.cs
Normal file
58
Chess-Challenge/src/Framework/Chess/Board/RepetitionTable.cs
Normal file
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@ -0,0 +1,58 @@
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using System;
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using System.Linq;
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namespace ChessChallenge.Chess
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{
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public class RepetitionTable
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{
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readonly ulong[] hashes;
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readonly int[] startIndices;
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int count;
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public RepetitionTable()
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{
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hashes = new ulong[256];
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startIndices = new int[hashes.Length];
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}
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public void Init(Board board)
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{
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ulong[] initialHashes = board.RepetitionPositionHistory.Reverse().ToArray();
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count = initialHashes.Length;
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for (int i = 0; i < initialHashes.Length; i++)
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{
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hashes[i] = initialHashes[i];
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startIndices[i] = 0;
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}
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startIndices[count] = 0;
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}
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public void Push(ulong hash, bool reset)
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{
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hashes[count] = hash;
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count++;
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startIndices[count] = reset ? count - 1 : startIndices[count - 1];
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}
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public void TryPop()
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{
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count = Math.Max(0, count - 1);
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}
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public bool Contains(ulong h)
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{
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int s = startIndices[count];
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// up to count-1 so that curr position is not counted
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for (int i = s; i < count - 1; i++)
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{
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if (hashes[i] == h)
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{
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return true;
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}
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}
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return false;
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}
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}
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}
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