/**
* Monte-Carlo simulation for playout.
*
* @param node Node to start at
* @param timeout Time limit
* @return Scores for all players
*/
private int[] playout(Node node, long timeout) {
if (node instanceof TerminalNode) {
return ((TerminalNode) node).goal;
}
MachineState state = ((NonTerminalNode) node).state;
while (System.currentTimeMillis() < timeout) {
if (theMachine.isTerminal(state)) {
List<Integer> s;
try {
s = theMachine.getGoals(state);
} catch (GoalDefinitionException e) {
System.err.println("Could not compute goal values.");
return null;
}
int[] scores = new int[s.size()];
for (int i = 0; i < scores.length; i++) {
scores[i] = s.get(i);
}
return scores;
}
try {
state = theMachine.getNextState(state, theMachine.getRandomJointMove(state));
} catch (TransitionDefinitionException e) {
System.err.println("Could not perform state update.");
return null;
} catch (MoveDefinitionException e) {
System.err.println("Could not compute legal moves.");
return null;
}
}
return null;
}
/**
* Performs one MCTS step.
*
* @param timeout Time limit
* @return Index of the move performed by the player in the root state
* @throws TimeoutException Time limit reached
*/
private int mctsStep(long timeout) {
List<NonTerminalNode> path = new ArrayList<NonTerminalNode>();
int[] scores = null;
Node current = root;
NonTerminalNode c = (NonTerminalNode) root;
// int rootMove = -1;
// Selection
List<List<Integer>> select = new ArrayList<List<Integer>>();
List<Move> selectM = new ArrayList<Move>();
while (current != null) {
if (System.currentTimeMillis() > timeout) {
return -1;
}
if (current instanceof TerminalNode) {
scores = ((TerminalNode) current).goal;
break;
}
c = (NonTerminalNode) current;
path.add(c);
List<Integer> selectEntry = new ArrayList<Integer>();
selectM = new ArrayList<Move>();
for (int p = 0; p < theMachine.getRoles().size(); p++) {
List<Move> moves = c.legal.get(p);
double bestval = Double.NEGATIVE_INFINITY;
Move bestmove;
int bestindex;
if (c.n == 0) {
bestmove = moves.get(0);
bestindex = 0;
} else {
bestmove = null;
bestindex = -1;
for (int i = 0; i < moves.size(); i++) {
Move m = moves.get(i);
double value = c.q_action[p][i] + uct(c.n, c.n_action[p][i]);
// System.out.println("Found a move with score " + value);
if (value > bestval) {
bestval = value;
bestmove = m;
bestindex = i;
}
}
}
selectEntry.add(bestindex);
selectM.add(bestmove);
}
select.add(selectEntry);
/*
if(current == root){
rootMove = select.get(select.size() - 1)[role];
}
*/
current = c.successors.get(selectEntry);
}
// Expansion & Playout
if (!(current instanceof TerminalNode)) {
MachineState next;
try {
next = theMachine.getNextState(c.state, selectM);
} catch (TransitionDefinitionException e) {
System.err.println("Could not perform state update.");
return -1;
}
if (theMachine.isTerminal(next)) {
current = new TerminalNode(next);
} else {
current = new NonTerminalNode(next);
}
c.successors.put(select.get(select.size() - 1), current);
scores = playout(current, timeout);
}
if (scores == null) {
return -1;
}
// Backpropagation
for (int i = 0; i < path.size(); i++) {
NonTerminalNode node = path.get(i);
node.n++;
for (int j = 0; j < theMachine.getRoles().size(); j++) {
node.n_action[j][select.get(i).get(j)]++;
node.q_action[j][select.get(i).get(j)] =
(node.q_action[j][select.get(i).get(j)] * node.n_action[j][select.get(i).get(j)]
+ scores[j])
/ (node.n_action[j][select.get(i).get(j)] + 1);
}
}
counter++;
return select.get(0).get(role);
}