//Reference:https://www.youtube.com/watch?v=UXW2yZndl7U
private MCTSNode RunMCTS(int player, float modifier)
{
MCTSNode root = new MCTSNode(size);
root.BoardState = mainBoard;
root.parent = null;
root.player = (activePlayer + 1) % 2;
root.score = 0.0f;
root.totalPlayouts = 0.0f;
int totalIterations = 0;
DateTime start = DateTime.Now;
//while((DateTime.Now - start).Milliseconds < Time.maximumDeltaTime * 1000 * modifier)
while (totalIterations < 100000)
{
MCTSNode current = root;
//Selection
while (current.children.Count != 0)
{
current = current.GetChildWithBestUCB1();
}
//Simulation
if (current.totalPlayouts == 0)
{
float score = Simulate(current.BoardState, activePlayer);
//Back Propagate
current.BackPropagate(score);
}
else
{
//Expansion
current.Expand();
}
totalIterations++;
}
//Find node with best score
float bestScore = root.children[0].score / root.children[0].totalPlayouts;
int selectedIndex = 0;
for (int i = 1; i < root.children.Count; i++)
{
float score = root.children[i].score / root.children[i].totalPlayouts;
if (bestScore < score)
{
bestScore = score;
selectedIndex = i;
}
}
return(root.children[selectedIndex]);
}
/// <summary>
/// Increment hits or misses according to the sign of the result
/// Have the parent node do this as well
/// </summary>
/// <param name="result"></param>
void BackPropagate(int result)
{
if (result > 0)
{
hits++;
}
if (result < 0)
{
misses++;
}
totalTrials++;
if (parent != null)
{
// parent active player is opposite of this active player
// so negate sign of result
parent.BackPropagate(-result);
}
}
