/// <summary>
/// Recursively searches a tree node and gives the evaluation for this node assuming best play for each player
/// </summary>
/// <param name="node">Current node</param>
/// <returns>Evaluation (pos: white advantage)</returns>
private double RecursiveEvaluateNode(TreeNode node)
{
InterlockedEngineStats.Increment_NodesVisited();
// End of recursion
if (node.Children is null)
{
return(Evaluation.GetEvaluation(node.Board));
}
// Assume that the enemy (child node) will make a best move for him
double enemySign = GetSign(!node.Board.IsWhiteToMove);
double bestEnemyMove = enemySign * WORST_SCORE;
foreach (var childNode in node.Children)
{
double enemyScore = RecursiveEvaluateNode(childNode);
if ((enemySign * enemyScore) > (enemySign * bestEnemyMove))
{
bestEnemyMove = enemyScore;
}
}
return(bestEnemyMove);
}
/// <summary>
/// Recursively searches a tree node and gives the evaluation for this node assuming best play for each player
/// </summary>
/// <param name="node">Current node</param>
/// <returns>Evaluation (pos: white advantage)</returns>
private double RecursiveEvaluateNode(TreeNode node, TextWriter tw, int depth)
{
InterlockedEngineStats.Increment_NodesVisited();
// End of recursion
if (node.Children.Count == 0)
{
double eval = Evaluation.GetEvaluation(node.Board);
for (int i = 0; i < depth; i++)
{
tw.Write('\t');
}
tw.Write(node.Board.IsWhiteToMove ? "w: " : "b: ");
tw.WriteLine(UCINotation.SerializeMove(node.Move) + " -> " + eval);
return(eval);
}
// Assume that the enemy (child node) will make a best move for him
double enemySign = GetSign(!node.Board.IsWhiteToMove);
double bestEnemyMove = enemySign * WORST_SCORE;
foreach (var childNode in node.Children)
{
double enemyScore = RecursiveEvaluateNode(childNode, tw, depth + 1);
if ((enemySign * enemyScore) > (enemySign * bestEnemyMove))
{
bestEnemyMove = enemyScore;
}
}
for (int i = 0; i < depth; i++)
{
tw.Write('\t');
}
tw.Write(node.Board.IsWhiteToMove ? "w: " : "b: ");
tw.WriteLine(UCINotation.SerializeMove(node.Move) + " -> " + bestEnemyMove);
return(bestEnemyMove);
}
public Move ReactToMove(IEnumerable <Move> moves)
{
// Make a move within the next 3 seconds
cancellationTokenSource = new CancellationTokenSource();
cancellationTokenSource.CancelAfter(5000);
var initialBoard = new Board(moves);
// Reset stats
InterlockedEngineStats.Reset();
// Start with the first tree layer
ConcurrentBag <TreeNode> lastTreeLayer = new ConcurrentBag <TreeNode>(initialBoard.GetLegalMoves().Select(x => new TreeNode()
{
Board = new Board(moves.Append(x)), // This is far from optimal, but ok since this is only done in init phase
Children = null,
Evaluation = double.NaN,
Parent = null,
Move = x
}));
// Start building a tree
List <TreeNode> gameTree = new List <TreeNode>(lastTreeLayer);
int depth = 0;
do
{
var newTreeLayer = new ConcurrentBag <TreeNode>();
Parallel.ForEach(lastTreeLayer, (parentNode, state) =>
{
parentNode.Children = new List <TreeNode>();
foreach (var possibleMove in parentNode.Board.GetLegalMoves())
{
// make a copy and change it
Board branchBoardAfterMove = (Board)(parentNode.Board.Clone());
branchBoardAfterMove.Mutate(possibleMove);
TreeNode childNode = new TreeNode()
{
Board = branchBoardAfterMove,
Children = null,
Evaluation = double.NaN,
Parent = parentNode,
IsComplete = false,
Move = possibleMove
};
newTreeLayer.Add(childNode);
parentNode.Children.Add(childNode);
}
parentNode.IsComplete = true;
if (cancellationTokenSource.IsCancellationRequested)
{
state.Stop();
}
});
if (cancellationTokenSource.IsCancellationRequested)
{
break;
}
InterlockedEngineStats.Update_MaxDepth(++depth);
// swap
lastTreeLayer = newTreeLayer;
if (depth >= MaxDepth)
{
break;
}
} while (!cancellationTokenSource.IsCancellationRequested);
// Traverse tree
StreamWriter sw = new StreamWriter("test.txt");
double bestScore = Sign(WORST_SCORE);
Move bestMove = gameTree.First().Move;
foreach (var candidate in gameTree)
{
double deepEvaluation = RecursiveEvaluateNode(candidate);
if (Sign(deepEvaluation) > Sign(bestScore))
{
bestScore = deepEvaluation;
bestMove = candidate.Move;
}
}
// turn file upside down
sw.Flush();
sw.Close();
File.WriteAllLines("test.txt", File.ReadAllLines("test.txt").Reverse());
InterlockedEngineStats.Set_Evaluation(bestScore);
return(bestMove);
}
