Randomise moves of equal value

TollyH · Nov 21, 2023 · a441b78 · a441b78
1 parent d000b42
commit a441b78
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Showing 2 changed files with 15 additions and 5 deletions.
diff --git a/BoardAnalysis.cs b/BoardAnalysis.cs
@@ -9,6 +9,8 @@ namespace Chess
 {
     public static class BoardAnalysis
     {
+        private static readonly Random rng = new();
+
         /// <summary>
         /// Determine whether a king can be reached by any of the opponents pieces
         /// </summary>
@@ -336,9 +338,10 @@ public PossibleMove(Point source, Point destination, double evaluatedFutureValue
         /// Use <see cref="EvaluatePossibleMoves"/> to find the best possible move in the current state of the game
         /// </summary>
         /// <param name="maxDepth">The maximum number of half-moves in the future to search</param>
-        public static async Task<PossibleMove> EstimateBestPossibleMove(ChessGame game, int maxDepth, CancellationToken cancellationToken)
+        /// <param name="randomise">Whether or not to randomise the order of moves that have the same score</param>
+        public static async Task<PossibleMove> EstimateBestPossibleMove(ChessGame game, int maxDepth, bool randomise, CancellationToken cancellationToken)
         {
-            PossibleMove[] moves = await EvaluatePossibleMoves(game, maxDepth, cancellationToken);
+            PossibleMove[] moves = await EvaluatePossibleMoves(game, maxDepth, randomise, cancellationToken);
             PossibleMove bestMove = new(default, default,
                 game.CurrentTurnWhite ? double.NegativeInfinity : double.PositiveInfinity, false, false, 0, 0, typeof(Pieces.Queen), new());
             foreach (PossibleMove potentialMove in moves)
@@ -377,8 +380,9 @@ public static async Task<PossibleMove> EstimateBestPossibleMove(ChessGame game,
         /// Evaluate each possible move in the current state of the game
         /// </summary>
         /// <param name="maxDepth">The maximum number of half-moves in the future to search</param>
+        /// <param name="randomise">Whether or not to randomise the order of moves that have the same score</param>
         /// <returns>An array of all possible moves, with information on board value and ability to checkmate</returns>
-        public static async Task<PossibleMove[]> EvaluatePossibleMoves(ChessGame game, int maxDepth, CancellationToken cancellationToken)
+        public static async Task<PossibleMove[]> EvaluatePossibleMoves(ChessGame game, int maxDepth, bool randomise, CancellationToken cancellationToken)
         {
             List<Task<PossibleMove>> evaluationTasks = new();
 
@@ -418,8 +422,14 @@ public static async Task<PossibleMove[]> EvaluatePossibleMoves(ChessGame game, i
             }
             try
             {
+                IEnumerable<PossibleMove> moves =
+                    (await Task.WhenAll(evaluationTasks)).Where(m => m.Source != m.Destination);
+                if (randomise)
+                {
+                    return moves.OrderBy(_ => rng.Next()).ToArray();
+                }
                 // Remove default moves from return value
-                return (await Task.WhenAll(evaluationTasks)).Where(m => m.Source != m.Destination).ToArray();
+                return moves.ToArray();
             }
             catch (TaskCanceledException)
             {

diff --git a/MainWindow.xaml.cs b/MainWindow.xaml.cs
@@ -530,7 +530,7 @@ private void UpdateEvaluationMeter(BoardAnalysis.PossibleMove? bestMove, bool wh
             {
                 return default;
             }
-            bestMove ??= await BoardAnalysis.EstimateBestPossibleMove(game, 4, cancellationToken);
+            bestMove ??= await BoardAnalysis.EstimateBestPossibleMove(game, 4, true, cancellationToken);
             return bestMove.Value;
         }