optimized move selection

Author: gkcs

src/main/java/main/java/codingame/TicTacToe/TicTacToe.java

@@ -23,7 +23,7 @@ public static void main(String args[]) throws IOException {
  largeBoard.play(2, opponentMove);
  algorithm.root = algorithm.root.getChild(opponentMove);
  algorithm.root.parent = null;
- algorithm.construct(largeBoard, 2);
+ algorithm.construct(largeBoard, 1);
  System.err.println(largeBoard);
  }
  final int validActionCount = Integer.parseInt(in.readLine());
@@ -36,12 +36,13 @@ public static void main(String args[]) throws IOException {
  largeBoard.play(1, bestMove);
  algorithm.root = algorithm.root.getChild(bestMove);
  algorithm.root.parent = null;
- algorithm.construct(largeBoard, 1);
+ algorithm.construct(largeBoard, 2);
  System.err.println(largeBoard);
  }
  }
 }
 
+//todo: write unit tests for each function
 class MCTS {
  public static final int TIME_OUT = 50;
  public static final double CONSTANT = 10000d;
@@ -51,7 +52,7 @@ public int suggestMove() {
  return root.getChildren()
  .stream()
  .max(Comparator.comparingDouble(node -> node.wins / (double) node.plays + node.plays / CONSTANT))
- .map(c -> c.col)
+ .map(c -> c.move)
  .orElseThrow(() -> new RuntimeException("No moves to play!"));
  }
 
@@ -60,7 +61,8 @@ public void construct(final LargeBoard board, int player) {
  while (System.currentTimeMillis() - startTime <= TIME_OUT) {
  TreeNode current = root;
  int position = current.selectChild(board);
- while (current.getChild(position) != null) {
+ //todo: Why do you check for canPlay?
+ while (board.canPlay(position) && current.getChild(position) != null) {
  current = current.getChild(position);
  board.play(player, position);
  position = current.selectChild(board);
@@ -80,15 +82,15 @@ public void construct(final LargeBoard board, int player) {
 class TreeNode {
  private static final Random random = new Random();
  public static final int SIMULATION_CONSTANT = 50;
- public final int col;
+ public final int move;
  public int plays;
  public double wins;
  public TreeNode parent;
  private final int player;
  private Map<Integer, TreeNode> children = new HashMap<>();
 
- public TreeNode(final int col, final TreeNode parent, final int player) {
- this.col = col;
+ public TreeNode(final int move, final TreeNode parent, final int player) {
+ this.move = move;
  this.parent = parent;
  this.player = player;
  }
@@ -98,21 +100,39 @@ public int selectChild(final LargeBoard board) {
  .stream()
  .max(Comparator.comparingDouble(TreeNode::getUtility));
  double maxUtility = child.map(TreeNode::getUtility).orElse(0d);
- int bestColumn = child.map(c -> c.col).orElse(0);
+ int bestColumn = child.map(c -> c.move).orElse(0);
  final Set<Integer> expandedSet = children.keySet();
  final int currentBoardIndex = board.currentBoard();
- int max = 81;
- int i = 0;
  if (currentBoardIndex != -1) {
- i = (currentBoardIndex / 3) * 27 + (currentBoardIndex % 3) * 3;
- max = i + 21;
- }
- for (; i < max; i++) {
- if (board.canPlay(i) && !expandedSet.contains(i)) {
- final double utility = Math.sqrt(Math.log(plays + 1)) + (0.05 / Math.abs(9 / 2.0 - i));
- if (utility > maxUtility) {
- maxUtility = utility;
- bestColumn = i;
+ int start = (currentBoardIndex / 3) * 27 + (currentBoardIndex % 3) * 3;
+ for (int x = 0; x < 3; x++, start++) {
+ for (int y = 0; y < 3; y++) {
+ int i = start + y * 9;
+ if (board.canPlay(i) && !expandedSet.contains(i)) {
+ final double utility = Math.sqrt(Math.log(plays + 1)) + (0.05 / Math.abs(40 - i));
+ if (utility > maxUtility) {
+ maxUtility = utility;
+ bestColumn = i;
+ }
+ }
+ }
+ }
+ } else {
+ for (int boardIndex = 0; boardIndex < 9; boardIndex++) {
+ if ((board.largeOccupied & (1 << boardIndex)) == 0) {
+ int start = (boardIndex / 3) * 27 + (boardIndex % 3) * 3;
+ for (int x = 0; x < 3; x++, start++) {
+ for (int y = 0; y < 3; y++) {
+ int i = start + y * 9;
+ if (board.canPlay(i) && !expandedSet.contains(i)) {
+ final double utility = Math.sqrt(Math.log(plays + 1)) + (0.05 / Math.abs(40 - i));
+ if (utility > maxUtility) {
+ maxUtility = utility;
+ bestColumn = i;
+ }
+ }
+ }
+ }
  }
  }
  }
@@ -127,19 +147,34 @@ private double simulate(final LargeBoard board, int player) {
  final int numberOfMovesPlayed = board.movesPlayed;
  final int originalPlayer = player;
  while (board.result() == -1) {
+ int movesToPlay = 0;
  final int currentBoardIndex = board.currentBoard();
- int max = 81;
- int position = 0;
+ final int possibilities[] = new int[currentBoardIndex != -1 ? 9 : 81];
  if (currentBoardIndex != -1) {
- position = (currentBoardIndex / 3) * 27 + (currentBoardIndex % 3) * 3;
- max = position + 21;
- }
- final int possibilities[] = new int[max - position];
- int movesToPlay = 0;
- for (; position < max; position++) {
- if (board.canPlay(position)) {
- possibilities[movesToPlay] = position;
- movesToPlay++;
+ int start = (currentBoardIndex / 3) * 27 + (currentBoardIndex % 3) * 3;
+ for (int x = 0; x < 3; x++, start++) {
+ for (int y = 0; y < 3; y++) {
+ int position = start + y * 9;
+ if (board.canPlay(position)) {
+ possibilities[movesToPlay] = position;
+ movesToPlay++;
+ }
+ }
+ }
+ } else {
+ for (int boardIndex = 0; boardIndex < 9; boardIndex++) {
+ if ((board.largeOccupied & (1 << boardIndex)) == 0) {
+ int start = (boardIndex / 3) * 27 + (boardIndex % 3) * 3;
+ for (int x = 0; x < 3; x++, start++) {
+ for (int y = 0; y < 3; y++) {
+ int position = start + y * 9;
+ if (board.canPlay(position)) {
+ possibilities[movesToPlay] = position;
+ movesToPlay++;
+ }
+ }
+ }
+ }
  }
  }
  if (movesToPlay == 0) {
@@ -188,14 +223,14 @@ public TreeNode getChild(final int col) {
  @Override
  public String toString() {
  return "TreeNode{" +
- "\ncol=" + col +
+ "\nmove=" + move +
  ", \nplays=" + plays +
  ", \nwins=" + wins +
- ", \nparent=" + (parent == null ? -1 : parent.col) +
+ ", \nparent=" + (parent == null ? -1 : parent.move) +
  ", \nplayer=" + player +
  ", \nchildren=" + children.values()
  .stream()
- .map(c -> "MOVE: " + c.col + " WINS: " + c.wins + " PLAYS: " + c.plays + "\n")
+ .map(node -> "MOVE: " + node.move + " WINS: " + node.wins + " PLAYS: " + node.plays + "\n")
  .collect(Collectors.joining("\n")) +
  '}';
  }
@@ -318,9 +353,9 @@ public int currentBoard() {
  @Override
  public String toString() {
  return "LargeBoard{" +
- "\nlargeBoard=" + largeBoard +
- ", \nlargeCaptures=" + largeCaptures +
- ", \nlargeOccupied=" + largeOccupied +
+ "\nlargeBoard=" + Integer.toBinaryString(largeBoard) +
+ ", \nlargeCaptures=" + Integer.toBinaryString(largeCaptures) +
+ ", \nlargeOccupied=" + Integer.toBinaryString(largeOccupied) +
  ", \nmovesPlayed=" + movesPlayed +
  ", \nmoves=" + Arrays.toString(moves) +
  ", \nboards=" + Arrays.deepToString(boards) +