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⚡ Replace GameState with an internal State class inside of Position and an array of instances - Reset() #2272

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⚡ Replace GameState with an internal State class inside of Position and an array of instances - Reset() #2272

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979cb5b
Wrap state-related position internals in PositionState
eduherminio Nov 19, 2025
aadf418
Make the state internal and handle it with an array of states
eduherminio Nov 19, 2025
c42a87d
Fix dev projects
eduherminio Nov 19, 2025
33cefd4
Merge remote-tracking branch 'origin/main' into refactor/gamestate-ar…
eduherminio Nov 19, 2025
a429494
⚡ Inline State (#2261)
eduherminio Nov 24, 2025
1548837
⚡ Avoid unnecessary big array allocations in Gamestate (#2262)
eduherminio Nov 24, 2025
be7a229
Merge with main
eduherminio Nov 27, 2025
782046f
Fix and integrate merge
eduherminio Nov 27, 2025
f4da203
Simplify PositionState
eduherminio Nov 27, 2025
d63911a
Implement reset method
eduherminio Nov 27, 2025
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8 changes: 4 additions & 4 deletions src/Lynx.Benchmark/MoveGenerator_SpanUnsafeAdd_Benchmark.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -822,10 +822,10 @@ private static bool IsAnyKingMoveValid(int piece, Position position, ref Evaluat
[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal static bool IsValidMove(Position position, Move move)
{
var gameState = position.MakeMove(move);
position.MakeMove(move);

bool result = position.WasProduceByAValidMove();
position.UnmakeMove(move, gameState);
position.UnmakeMove(move);

return result;
}
Expand Down Expand Up @@ -1499,10 +1499,10 @@ private static bool IsAnyKingMoveValid(int piece, Position position, ref Evaluat
[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal static bool IsValidMove(Position position, Move move)
{
var gameState = position.MakeMove(move);
position.MakeMove(move);

bool result = position.WasProduceByAValidMove();
position.UnmakeMove(move, gameState);
position.UnmakeMove(move);

return result;
}
Expand Down
24 changes: 9 additions & 15 deletions src/Lynx.Benchmark/ParseGame_Benchmark.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -525,9 +525,9 @@ internal OriginalGame(string fen, string[] movesUCIString) : this(fen)
}

[MethodImpl(MethodImplOptions.AggressiveInlining)]
public GameState MakeMove(Move moveToPlay)
public void MakeMove(Move moveToPlay)
{
var gameState = CurrentPosition.MakeMove(moveToPlay);
CurrentPosition.MakeMove(moveToPlay);

if (CurrentPosition.WasProduceByAValidMove())
{
Expand All @@ -538,13 +538,11 @@ public GameState MakeMove(Move moveToPlay)
else
{
_logger.Warn("Error trying to play {0}", moveToPlay.UCIString());
CurrentPosition.UnmakeMove(moveToPlay, gameState);
CurrentPosition.UnmakeMove(moveToPlay);
}

PositionHashHistory.Add(CurrentPosition.UniqueIdentifier);
HalfMovesWithoutCaptureOrPawnMove = Utils.Update50movesRule(moveToPlay, HalfMovesWithoutCaptureOrPawnMove);

return gameState;
}
}

Expand Down Expand Up @@ -608,9 +606,9 @@ internal ImprovedGame(string fen, ReadOnlySpan<char> rawMoves, Span<Range> range
}

[MethodImpl(MethodImplOptions.AggressiveInlining)]
public GameState MakeMove(Move moveToPlay)
public void MakeMove(Move moveToPlay)
{
var gameState = CurrentPosition.MakeMove(moveToPlay);
CurrentPosition.MakeMove(moveToPlay);

if (CurrentPosition.WasProduceByAValidMove())
{
Expand All @@ -621,13 +619,11 @@ public GameState MakeMove(Move moveToPlay)
else
{
_logger.Warn("Error trying to play {0}", moveToPlay.UCIString());
CurrentPosition.UnmakeMove(moveToPlay, gameState);
CurrentPosition.UnmakeMove(moveToPlay);
}

PositionHashHistory.Add(CurrentPosition.UniqueIdentifier);
HalfMovesWithoutCaptureOrPawnMove = Utils.Update50movesRule(moveToPlay, HalfMovesWithoutCaptureOrPawnMove);

return gameState;
}
}

Expand Down Expand Up @@ -695,9 +691,9 @@ public ImprovedGame2(ReadOnlySpan<char> fen, ReadOnlySpan<char> rawMoves, Span<R
}

[MethodImpl(MethodImplOptions.AggressiveInlining)]
public GameState MakeMove(Move moveToPlay)
public void MakeMove(Move moveToPlay)
{
var gameState = CurrentPosition.MakeMove(moveToPlay);
CurrentPosition.MakeMove(moveToPlay);

if (CurrentPosition.WasProduceByAValidMove())
{
Expand All @@ -708,13 +704,11 @@ public GameState MakeMove(Move moveToPlay)
else
{
_logger.Warn("Error trying to play {0}", moveToPlay.UCIString());
CurrentPosition.UnmakeMove(moveToPlay, gameState);
CurrentPosition.UnmakeMove(moveToPlay);
}

PositionHashHistory.Add(CurrentPosition.UniqueIdentifier);
HalfMovesWithoutCaptureOrPawnMove = Utils.Update50movesRule(moveToPlay, HalfMovesWithoutCaptureOrPawnMove);

return gameState;
}
}

Expand Down
9 changes: 4 additions & 5 deletions src/Lynx.Benchmark/TryParseFromUCIString_Benchmark.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -232,10 +232,11 @@ public TryParseFromUCIString_Benchmark_Game(ReadOnlySpan<char> fen, ReadOnlySpan

_gameInitialPosition = new Position(CurrentPosition);
}

[MethodImpl(MethodImplOptions.AggressiveInlining)]
public GameState MakeMove(Move moveToPlay)
public void MakeMove(Move moveToPlay)
{
var gameState = CurrentPosition.MakeMove(moveToPlay);
CurrentPosition.MakeMove(moveToPlay);

if (CurrentPosition.WasProduceByAValidMove())
{
Expand All @@ -246,13 +247,11 @@ public GameState MakeMove(Move moveToPlay)
else
{
_logger.Warn("Error trying to play {0}", moveToPlay.UCIString());
CurrentPosition.UnmakeMove(moveToPlay, gameState);
CurrentPosition.UnmakeMove(moveToPlay);
}

PositionHashHistory.Add(CurrentPosition.UniqueIdentifier);
HalfMovesWithoutCaptureOrPawnMove = Utils.Update50movesRule(moveToPlay, HalfMovesWithoutCaptureOrPawnMove);

return gameState;
}
}
}
12 changes: 6 additions & 6 deletions src/Lynx.Dev/Program.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -529,7 +529,7 @@ static void GeneralMoveTest(Game game)
game.CurrentPosition.Print();

Console.WriteLine(move.ToEPDString(game.CurrentPosition));
var gameState = game.MakeMove(move);
game.MakeMove(move);
game.CurrentPosition.Print();

Console.WriteLine("White occupancy:");
Expand All @@ -538,7 +538,7 @@ static void GeneralMoveTest(Game game)
Console.WriteLine("Black occupancy:");
game.CurrentPosition.OccupancyBitBoards[(int)Side.Black].Print();

game.CurrentPosition.UnmakeMove(move, gameState);
game.CurrentPosition.UnmakeMove(move);
}
}

Expand All @@ -552,9 +552,9 @@ static void CastlingRightsTest(Game game)
game.CurrentPosition.Print();

Console.WriteLine(move.ToEPDString(game.CurrentPosition));
var gameState = game.MakeMove(move);
game.MakeMove(move);
game.CurrentPosition.Print();
game.CurrentPosition.UnmakeMove(move, gameState);
game.CurrentPosition.UnmakeMove(move);
}
}
}
Expand Down Expand Up @@ -1118,14 +1118,14 @@ static void TestMoveGen(string fen)

var newPosition = new Position(position);
newPosition.MakeMove(move);
var savedState = position.MakeMove(move);
position.MakeMove(move);

Console.WriteLine($"Position\t{newPosition.FEN()}, Zobrist key {newPosition.UniqueIdentifier}");
Console.WriteLine($"Position\t{position.FEN()}, Zobrist key {position.UniqueIdentifier}");

Console.WriteLine($"Unmaking {epdMoveString} in\t{position.FEN()}");

//position.UnmakeMove(move, savedState);
//position.UnmakeMove(move);

Console.WriteLine($"Position\t{position.FEN()}, Zobrist key {position.UniqueIdentifier}");

Expand Down
1 change: 1 addition & 0 deletions src/Lynx/Engine.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -130,6 +130,7 @@ public SearchResult BestMove(in SearchConstraints searchConstrains, bool isPonde
SearchResult resultToReturn = IDDFS(isPondering, jointCts.Token);
//SearchResult resultToReturn = await SearchBestMove(maxDepth, decisionTime);

// This is done to allow sending consecutive search commands
Game.ResetCurrentPositionToBeforeSearchState();
if (!isPondering
&& resultToReturn.BestMove != default
Expand Down
48 changes: 24 additions & 24 deletions src/Lynx/Evaluation.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -91,16 +91,16 @@ public partial class Position
int blackPawnKingRingAttacks = (blackPawnAttacks & KingRing[whiteKing]).CountBits();
evaluationContext.IncreaseKingRingAttacks((int)Side.Black, blackPawnKingRingAttacks);

if (IsIncrementalEval)
if (_state.IsIncrementalEval)
{
packedScore = IncrementalEvalAccumulator;
gamePhase = IncrementalPhaseAccumulator;
packedScore = _state.IncrementalEvalAccumulator;
gamePhase = _state.IncrementalPhaseAccumulator;

var kingPawnIndex = _kingPawnUniqueIdentifier & Constants.KingPawnHashMask;
var kingPawnIndex = _state.KingPawnUniqueIdentifier & Constants.KingPawnHashMask;
ref var entry = ref pawnEvalTable[kingPawnIndex];

// pawnEvalTable hit: We can reuse cached eval for pawn additional evaluation + PieceProtectedByPawnBonus + KingShieldBonus
if (entry.Key == _kingPawnUniqueIdentifier)
if (entry.Key == _state.KingPawnUniqueIdentifier)
{
packedScore += entry.PackedScore;
}
Expand Down Expand Up @@ -152,7 +152,7 @@ public partial class Position
// Pawn islands
pawnScore += PawnIslands(whitePawns, blackPawns);

entry.Update(_kingPawnUniqueIdentifier, pawnScore);
entry.Update(_state.KingPawnUniqueIdentifier, pawnScore);
packedScore += pawnScore;
}

Expand Down Expand Up @@ -191,14 +191,14 @@ public partial class Position
}
else
{
IncrementalEvalAccumulator = 0;
IncrementalPhaseAccumulator = 0;
_state.IncrementalEvalAccumulator = 0;
_state.IncrementalPhaseAccumulator = 0;

var kingPawnIndex = _kingPawnUniqueIdentifier & Constants.KingPawnHashMask;
var kingPawnIndex = _state.KingPawnUniqueIdentifier & Constants.KingPawnHashMask;
ref var entry = ref pawnEvalTable[kingPawnIndex];

// pawnTable hit: We can reuse cached eval for pawn additional evaluation + PieceProtectedByPawnBonus + KingShieldBonus
if (entry.Key == _kingPawnUniqueIdentifier)
if (entry.Key == _state.KingPawnUniqueIdentifier)
{
packedScore += entry.PackedScore;

Expand All @@ -211,7 +211,7 @@ public partial class Position
{
whitePawnsCopy = whitePawnsCopy.WithoutLS1B(out var pieceSquareIndex);

IncrementalEvalAccumulator += PSQT(whiteBucket, blackBucket, (int)Piece.P, pieceSquareIndex);
_state.IncrementalEvalAccumulator += PSQT(whiteBucket, blackBucket, (int)Piece.P, pieceSquareIndex);

// No incremental eval - included in pawn table | packedScore += AdditionalPieceEvaluation(...);
}
Expand All @@ -225,7 +225,7 @@ public partial class Position
{
blackPawnsCopy = blackPawnsCopy.WithoutLS1B(out var pieceSquareIndex);

IncrementalEvalAccumulator += PSQT(blackBucket, whiteBucket, (int)Piece.p, pieceSquareIndex);
_state.IncrementalEvalAccumulator += PSQT(blackBucket, whiteBucket, (int)Piece.p, pieceSquareIndex);

// No incremental eval - included in pawn table | packedScore -= AdditionalPieceEvaluation(...);
}
Expand All @@ -249,7 +249,7 @@ public partial class Position
{
whitePawnsCopy = whitePawnsCopy.WithoutLS1B(out var pieceSquareIndex);

IncrementalEvalAccumulator += PSQT(whiteBucket, blackBucket, (int)Piece.P, pieceSquareIndex);
_state.IncrementalEvalAccumulator += PSQT(whiteBucket, blackBucket, (int)Piece.P, pieceSquareIndex);

pawnScore += PawnAdditionalEvaluation(ref evaluationContext, whiteBucket, blackBucket, pieceSquareIndex, (int)Piece.P, whiteKing, blackKing);
}
Expand All @@ -268,15 +268,15 @@ public partial class Position
{
blackPawnsCopy = blackPawnsCopy.WithoutLS1B(out var pieceSquareIndex);

IncrementalEvalAccumulator += PSQT(blackBucket, whiteBucket, (int)Piece.p, pieceSquareIndex);
_state.IncrementalEvalAccumulator += PSQT(blackBucket, whiteBucket, (int)Piece.p, pieceSquareIndex);

pawnScore -= PawnAdditionalEvaluation(ref evaluationContext, blackBucket, whiteBucket, pieceSquareIndex, (int)Piece.p, blackKing, whiteKing);
}

// Pawn islands
pawnScore += PawnIslands(whitePawns, blackPawns);

entry.Update(_kingPawnUniqueIdentifier, pawnScore);
entry.Update(_state.KingPawnUniqueIdentifier, pawnScore);
packedScore += pawnScore;
}

Expand All @@ -292,9 +292,9 @@ public partial class Position
{
bitboard = bitboard.WithoutLS1B(out var pieceSquareIndex);

IncrementalEvalAccumulator += PSQT(whiteBucket, blackBucket, pieceIndex, pieceSquareIndex);
_state.IncrementalEvalAccumulator += PSQT(whiteBucket, blackBucket, pieceIndex, pieceSquareIndex);

IncrementalPhaseAccumulator += GamePhaseByPiece[pieceIndex];
_state.IncrementalPhaseAccumulator += GamePhaseByPiece[pieceIndex];

packedScore += AdditionalPieceEvaluation(ref evaluationContext, pieceSquareIndex, whiteBucket, blackBucket, pieceIndex, (int)Side.White, blackPawnAttacks, blackKing);
}
Expand All @@ -313,17 +313,17 @@ public partial class Position
{
bitboard = bitboard.WithoutLS1B(out var pieceSquareIndex);

IncrementalEvalAccumulator += PSQT(blackBucket, whiteBucket, pieceIndex, pieceSquareIndex);
_state.IncrementalEvalAccumulator += PSQT(blackBucket, whiteBucket, pieceIndex, pieceSquareIndex);

IncrementalPhaseAccumulator += GamePhaseByPiece[pieceIndex];
_state.IncrementalPhaseAccumulator += GamePhaseByPiece[pieceIndex];

packedScore -= AdditionalPieceEvaluation(ref evaluationContext, pieceSquareIndex, blackBucket, whiteBucket, pieceIndex, (int)Side.Black, whitePawnAttacks, whiteKing);
}
}

packedScore += IncrementalEvalAccumulator;
gamePhase += IncrementalPhaseAccumulator;
IsIncrementalEval = true;
packedScore += _state.IncrementalEvalAccumulator;
gamePhase += _state.IncrementalPhaseAccumulator;
_state.IsIncrementalEval = true;
}

// Kings - they can't be incremental due to the king buckets
Expand Down Expand Up @@ -519,8 +519,8 @@ public partial class Position
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public int Phase()
{
var gamePhase = IsIncrementalEval
? IncrementalPhaseAccumulator
var gamePhase = _state.IsIncrementalEval
? _state.IncrementalPhaseAccumulator
: PhaseFromScratch();

return (gamePhase > MaxPhase) // Early promotions
Expand Down
11 changes: 4 additions & 7 deletions src/Lynx/Model/Game.cs
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Expand Up @@ -67,7 +67,6 @@ public void ParsePositionCommand(ReadOnlySpan<char> positionCommandSpan)
{
try
{

// We divide the position command in these two sections:
// "position startpos ||"
// "position startpos || moves e2e4 e7e5"
Expand Down Expand Up @@ -266,9 +265,9 @@ public static bool IsThreefoldRepetition(ReadOnlySpan<ulong> positionHashHistory
public static bool Is50MovesRepetition(int halfMovesWithoutCaptureOrPawnMove) => halfMovesWithoutCaptureOrPawnMove >= 100;

[MethodImpl(MethodImplOptions.AggressiveInlining)]
public GameState MakeMove(Move moveToPlay)
public void MakeMove(Move moveToPlay)
{
var gameState = CurrentPosition.MakeMove(moveToPlay);
CurrentPosition.MakeMove(moveToPlay);

if (CurrentPosition.WasProduceByAValidMove())
{
Expand All @@ -280,17 +279,15 @@ public GameState MakeMove(Move moveToPlay)
}
else
{
CurrentPosition.UnmakeMove(moveToPlay, gameState);
CurrentPosition.UnmakeMove(moveToPlay);
_logger.Warn("Error trying to play move {0} in {1}", moveToPlay.UCIString(), CurrentPosition.FEN(HalfMovesWithoutCaptureOrPawnMove));
}

return gameState;
}

/// <summary>
/// Cleans <see cref="CurrentPosition"/> value, since in case of search cancellation
/// (either by the engine time management logic or by external stop command)
/// currentPosition won't be the initial one
/// currentPosition won't be the initial one.
/// </summary>
public void ResetCurrentPositionToBeforeSearchState()
{
Expand Down
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