private void expand(MctsNode node)
{
// If there are no more moves, stop it
var availableMoves = getAvailableMoves(node.Board, node.Board.NextPlayer);
if (availableMoves == null || availableMoves.Count() == 0)
{
return;
}
int i = 0;
foreach (var move in availableMoves)
{
var newBoard = (CheckerBoard)node.Board.Clone();
newBoard.MakeMove(move, node.Board.NextPlayer);
var childNode = new MctsNode(move, newBoard);
childNode.Visits++;
childNode.Name += node.Name + $"-{i++}";
node.Children.Add(childNode);
}
node.IsExpanded = true;
}
private bool runRandomSimulation(MctsNode node, Player invokingPlayer)
{
var board = (CheckerBoard)node.Board.Clone();
int turns = 0;
while (board.GetGameStatus() == GameStatuses.Running && turns < MAX_DEPTH)
{
var availableMoves = getAvailableMoves(board, board.NextPlayer);
if (availableMoves != null && availableMoves.Count() > 0)
{
var randomMove = listHelper.Random(availableMoves);
board.MakeMove(randomMove, board.NextPlayer);
}
turns++;
}
if (board.GetGameStatus() != GameStatuses.Running && board.NextPlayer == invokingPlayer)
{
return(true);
}
else
{
return(false);
}
}
private double ucb(MctsNode child, MctsNode parent)
{
var result = child.Wins / (double)child.Visits + balanceConstant * Math.Sqrt(2 * Math.Log(parent.Visits) / child.Visits);
//Debug.WriteLine($"UCT for {child.Name}: CV={child.Visits}; CW={child.Wins}; PV={parent.Visits}; R={result}");
return(result);
}
private bool runSimulationWithDfs(MctsNode node, Player invokingPlayer)
{
var board = (CheckerBoard)node.Board.Clone();
int turns = 0;
while (board.GetGameStatus() == GameStatuses.Running && turns < MAX_TURNS)
{
var dfs = new DfsAI(3, listHelper);
var move = dfs.GetMove(board, board.NextPlayer);
board.MakeMove(move, board.NextPlayer);
/*var availableMoves = getAvailableMoves(board, board.NextPlayer);
* if (availableMoves != null && availableMoves.Count() > 0)
* {
* var randomMove = listHelper.Random(availableMoves);
* board.MakeMove(randomMove, board.NextPlayer);
* }*/
turns++;
}
if (board.GetGameStatus() != GameStatuses.Running && board.NextPlayer == invokingPlayer)
{
return(true);
}
else
{
return(false);
}
}
private double runRandomSimulation(MctsNode node, Player invokingPlayer)
{
var board = (CheckerBoard)node.Board.Clone();
int turns = 0;
while (board.GetGameStatus() == GameStatuses.Running && turns < MAX_TURNS)
{
var availableMoves = getAvailableMoves(board, board.NextPlayer);
if (availableMoves != null && availableMoves.Count() > 0)
{
var randomMove = listHelper.Random(availableMoves);
board.MakeMove(randomMove, board.NextPlayer);
}
turns++;
}
if (board.GetGameStatus() != GameStatuses.Running && board.NextPlayer == invokingPlayer)
{
//Debug.WriteLine($"Finished in turns {turns}");
var res = (MAX_TURNS - turns) / ((double)MAX_TURNS / 2d);
return(res);
}
else
{
return(-1d);
}
}
private MctsNode getFinalBestChild(MctsNode node)
{
if (node == null)
{
throw new ArgumentNullException("node");
}
if (node.Children == null)
{
throw new ArgumentNullException("node.Children");
}
if (node.Children.Count() == 0)
{
throw new ArgumentException("Node must have at least one child.", "node.Children");
}
//Debug.WriteLine($"Get best child of {node.Name}");
/*var orderedNodes = node.Children.OrderByDescending(c => ucb(c, node)).ThenBy(o => randomService.NextDouble());
* var bestNode = orderedNodes.First();
* return bestNode;*/
var orderedNodes = node.Children.OrderByDescending(c => c.Reward / c.Visits).ThenBy(o => randomService.NextDouble());
var bestNode = orderedNodes.First();
return(bestNode);
}
private MctsNode getBestChild(MctsNode node)
{
if (node == null)
{
throw new ArgumentNullException("node");
}
if (node.Children == null)
{
throw new ArgumentNullException("node.Children");
}
if (node.Children.Count() == 0)
{
throw new ArgumentException("Node must have at least one child.", "node.Children");
}
//Debug.WriteLine($"Get best child of {node.Name}");
var orderedNodes = node.Children.OrderByDescending(c => ucb(c, node)).ThenBy(o => randomService.NextDouble());
var bestNode = orderedNodes.First();
return(bestNode);
//var randChild = listHelper.Random(node.Children);
// return randChild;
}
public Move GetMove(CheckerBoard currentBoard, Player invokingPlayer)
{
var root = new MctsNode(null, currentBoard);
root.Name = "0";
MctsNode currentNode = root;
var visitedNodes = new List <MctsNode>();
var executionStopwatch = new Stopwatch();
executionStopwatch.Start();
var iterations = 0;
while (executionStopwatch.Elapsed <= MAX_DURATION)//(++iterations <= 1000) //
{
iterations++;
visitedNodes.Add(currentNode);
currentNode.Visits++;
// If current node is expanded, it will find best child, and go one leven down
if (currentNode.IsExpanded)
{
// Find best child
var bestChild = getBestChild(currentNode);
currentNode = bestChild;
}
else
{
// If node is not expanded, it expands it, and runs simulation from random child
expand(currentNode);
var isWin = false;
if (currentNode.Children.Count() > 0)
{
var bestChild = getBestChild(currentNode);
visitedNodes.Add(bestChild);
bestChild.Visits++;
// Run random simulation from this point
isWin = runRandomSimulation(bestChild, invokingPlayer);
}
// Backpropagate results
backpropageate(visitedNodes, isWin);
// Reset path to start from root
currentNode = root;
visitedNodes.Clear();
}
}
// Save tree
//TreeJsonSaver.Save("mcts", root);
Console.WriteLine($"MCTS iteratiosn: {iterations}");
// Find best
var best = getBestChild(root);
return(best.Move);
}