private static void MCRollout(Node leaf)
{
Con4Board board = leaf.state;
int player = leaf.playerToMove;
int value = 0;
BoardState bs = leaf.bs;
while (true)
{
//BoardState bs = board.EvaluateBoard();
//checkEqualityOfEval(board, bs);
if (bs != BoardState.ongoing)
{
value = BoardStateToValue(bs);
break;
}
else
{
List <int> possMoves = board.GetPossibleMoves();
board = board.SimulateMove(player, possMoves[rnd.Next(possMoves.Count)]);
simulations++;
bs = Evaluate.EvaluateBoard(board);
evaluations++;
player *= -1;
}
}
Backpropagate(leaf, value);
}
private static void HandleLeafNode(Node leaf)
{
if (leaf.totalVisits == 0)
{
MCRollout(leaf);
}
else
{
// EXPAND
Con4Board board = leaf.state;
//BoardState bs = board.EvaluateBoard();
//checkEqualityOfEval(board, bs);
//BoardState bs = Evaluate.EvaluateBoard(board);
BoardState bs = leaf.bs;
//evaluations++;
if (bs != BoardState.ongoing) // Terminal node, do not expand, just backprop
{
Backpropagate(leaf, BoardStateToValue(bs));
}
else // Not terminal, expand
{
List <int> possMoves = board.GetPossibleMoves();
foreach (int move in possMoves)
{
leaf.children.Add(new Node(leaf, board.SimulateMove(leaf.playerToMove, move),
leaf.playerToMove * -1, move));
simulations++;
}
Node firstChild = leaf.children[0];
MCRollout(firstChild);
}
}
}
public static int FindMove(Con4Board board, long searchTimeMs)
{
simulations = 0;
evaluations = 0;
if (root == null)
{
// New tree
root = new Node(null, board, 1, -1);
List <int> possMoves = board.GetPossibleMoves();
foreach (int move in possMoves)
{
root.children.Add(new Node(root, board.SimulateMove(root.playerToMove, move),
root.playerToMove * -1, move));
simulations++;
}
}
else
{
// Continue from last tree
// Set root to child which matches opponents move
foreach (Node node in root.children)
{
if (node.state.Equals(board))
{
root = node;
root.parent = null; // Let GC remove rest of tree
Console.WriteLine("Found root, continuing where we left off!");
break;
}
}
}
stopwatch.Restart();
while (stopwatch.ElapsedMilliseconds < searchTimeMs)
{
//stopwatch.Restart();
for (int i = 0; i < 100; i++)
{
MCTSIteration();
}
//stopwatch.Stop();
//Console.WriteLine(stopwatch.ElapsedMilliseconds);
//searchTimeMs -= stopwatch.ElapsedMilliseconds;
}
List <Node> children = root.children;
int bestMove = children[0].previousMove;
double bestValue = children[0].totalValue;
Node nextRoot = children[0]; // To continue on same tree next move
Console.Write("Move values {m, v}: ");
Console.Write("{" + children[0].previousMove + ", " + children[0].totalValue + "} ");
for (int i = 1; i < children.Count; i++)
{
Node child = children[i];
double totVal = child.totalValue;
Console.Write("{" + child.previousMove + ", " + totVal + "}");
if (totVal > bestValue)
{
bestValue = totVal;
bestMove = child.previousMove;
nextRoot = child;
}
}
Console.WriteLine(" => Playing move: " + bestMove);
Console.WriteLine("Simulations: " + simulations + ", Evaluations: " + evaluations);
root = nextRoot;
return(bestMove);
}