/// <summary>
/// Selects the child with the highest relative reward.
/// </summary>
/// <param name="node">A node.</param>
/// <exception cref="ArgumentNullException">Is thrown, if the given node is null.</exception>
/// <exception cref="InvalidOperationException">Is thrown, if no child nodes are available.</exception>
public IGameTreeNode finalChildSelection(IGameTreeNode node)
{
if (node == null)
{
throw new ArgumentNullException("CLASS: FinalChildSelectionServiceMAX, METHOD: finalChildSelection - the given node is null!");
}
if (!node.areChildNodesExpanded)
{
throw new InvalidOperationException("CLASS: FinalChildSelectionServiceMAX, METHOD: finalChildSelection - no child nodes are available!");
}
double maxScore = 0;
List <IGameTreeNode> bestChilds = new List <IGameTreeNode>();
foreach (IGameTreeNode child in node.getChildNodes())
{
if (child.value / child.playouts >= maxScore)
{
if (child.value / child.playouts > maxScore)
{
maxScore = child.value / child.playouts;
bestChilds.Clear();
}
bestChilds.Add(child);
}
}
Random rng = new Random();
return(bestChilds[rng.Next(bestChilds.Count)]);
}
public static IMctsableGameState calculateGameStateFromNode(MctsNode node)
{
List <IGameTreeNode> pathInTheGameTree = new List <IGameTreeNode>();
IGameTreeNode currentNode = node;
pathInTheGameTree.Add(node);
while (currentNode.previousNode != null)
{
pathInTheGameTree.Insert(0, currentNode.previousNode);
currentNode = currentNode.previousNode;
}
MctsRootNode rootNode = currentNode as MctsRootNode;
if (rootNode == null)
{
throw new InvalidOperationException("CLASS: MctsNode, METHOD: calculateGameStateFromNode - no root node available in game tree!");
}
IMctsableGameState gameState = rootNode.initialGameState.duplicate();
pathInTheGameTree.RemoveAt(0);
foreach (MctsNode pathNode in pathInTheGameTree)
{
gameState.makeMove(pathNode.move);
}
return(gameState);
}
/// <summary>
/// Selects the best child of the given node via the RAVE algorithm.
/// </summary>
/// <param name="node">A node in the game tree.</param>
/// <param name="explorationConstant">A tunable exploration constant.</param>
/// <exception cref="ArgumentNullException">Is thrown, if the given node is null.</exception>
/// <exception cref="InvalidOperationException">Is thrown, if no child nodes are available.</exception>
public IGameTreeNode childSelection(IGameTreeNode node, double explorationConstant)
{
if (node == null)
{
throw new ArgumentNullException("CLASS: ChildSelectionServiceRAVE, METHOD: childSelection - given node is null!");
}
if (!node.areChildNodesExpanded)
{
throw new InvalidOperationException("CLASS: ChildSelectionServiceRAVE, METHOD: childSelection - no child nodes are available!");
}
double score, maxScore = 0, alpha;
List <IGameTreeNode> bestChildren = new List <IGameTreeNode>();
foreach (IGameTreeNode child in node.getChildNodes())
{
if (child.playouts == 0)
{
return(child);
}
alpha = Math.Max(0, (double)(_playoutsBound - child.playouts) / _playoutsBound);
score = alpha * child.valueAMAF + (1 - alpha) * child.value + explorationConstant * Math.Sqrt(Math.Log(node.playouts) / child.playouts);
if (score >= maxScore)
{
if (score > maxScore)
{
maxScore = score;
bestChildren.Clear();
}
bestChildren.Add(child);
}
}
Random rng = new Random();
return(bestChildren[rng.Next(bestChildren.Count)]);
}