mcts v1, v2, v3, v4 done. v5 wip

game/src/main/java/org/toop/game/BitboardGame.java

@@ -6,7 +6,6 @@ import org.toop.framework.gameFramework.model.game.TurnBasedGame;
 import org.toop.framework.gameFramework.model.player.Player;
 
 import java.util.Arrays;
-import java.util.concurrent.atomic.AtomicInteger;
 
 // There is AI performance to be gained by getting rid of non-primitives and thus speeding up deepCopy
 public abstract class BitboardGame<T extends BitboardGame<T>> implements TurnBasedGame<T> {
@@ -19,7 +18,7 @@ public abstract class BitboardGame<T extends BitboardGame<T>> implements TurnBas
 
 	// long is 64 bits. Every game has a limit of 64 cells maximum.
 	private final long[] playerBitboard;
-	private int currentTurn = 0;
+	protected int currentTurn = 0;
 
 	public BitboardGame(int columnSize, int rowSize, int playerCount, Player<T>[] players) {
 		this.columnSize = columnSize;
@@ -82,10 +81,6 @@ public abstract class BitboardGame<T extends BitboardGame<T>> implements TurnBas
 		return (currentTurn + 1) % playerBitboard.length;
 	}
 
-    public Player<T> getCurrentPlayer(){
-        return players[getCurrentPlayerIndex()];
-    }
-
 	@Override
 	public PlayResult getState() {
 		return state;

game/src/main/java/org/toop/game/games/reversi/BitboardReversi.java

@@ -6,9 +6,6 @@ import org.toop.framework.gameFramework.model.player.Player;
 import org.toop.game.BitboardGame;
 
 public class BitboardReversi extends BitboardGame<BitboardReversi> {
-
-    public record Score(int black, int white) {}
-
 	private final long notAFile = 0xfefefefefefefefeL;
 	private final long notHFile = 0x7f7f7f7f7f7f7f7fL;
 
@@ -253,7 +250,9 @@ public class BitboardReversi extends BitboardGame<BitboardReversi> {
 	}
 
     @Override
-    public BitboardReversi deepCopy() {return new BitboardReversi(this);}
+	public BitboardReversi deepCopy() {
+		return new BitboardReversi(this);
+	}
 
 	public PlayResult play(long move) {
 		final long flips = getFlips(move);
@@ -296,13 +295,6 @@ public class BitboardReversi extends BitboardGame<BitboardReversi> {
 		return state;
 	}
 
-	public Score getScore() {
-		return new Score(
-			Long.bitCount(getPlayerBitboard(0)),
-			Long.bitCount(getPlayerBitboard(1))
-		);
-	}
-
     public int getWinner(){
         final long black = getPlayerBitboard(0);
         final long white = getPlayerBitboard(1);
@@ -316,8 +308,51 @@ public class BitboardReversi extends BitboardGame<BitboardReversi> {
         else if (blackCount > whiteCount){
             return 0;
         }
-        else{
+        else {
             return 1;
         }
     }
+
+	@Override
+	public float rateMove(long move) {
+		final long corners = 0x8100000000000081L;
+
+		if ((move & corners) != 0L) {
+			return 0.4f;
+		}
+
+		final long xSquares = 0x0042000000004200L;
+
+		if ((move & xSquares) != 0) {
+			return -0.4f;
+		}
+
+		final long cSquares = 0x4281000000008142L;
+
+		if ((move & cSquares) != 0) {
+			return -0.1f;
+		}
+
+		return 0.0f;
+	}
+
+	@Override
+	public long heuristicMove(long legalMoves) {
+		long bestMove = 0L;
+		float bestMoveRate = Float.NEGATIVE_INFINITY;
+
+		while (legalMoves != 0L) {
+			final long move = legalMoves & -legalMoves;
+			final float moveRate = rateMove(move);
+
+			if (moveRate > bestMoveRate) {
+				bestMove = move;
+				bestMoveRate = moveRate;
+			}
+
+			legalMoves &= ~move;
+		}
+
+		return bestMove;
+	}
 }

game/src/main/java/org/toop/game/games/tictactoe/BitboardTicTacToe.java

@@ -104,4 +104,14 @@ public class BitboardTicTacToe extends BitboardGame<BitboardTicTacToe> {
     public BitboardTicTacToe deepCopy() {
         return new BitboardTicTacToe(this);
     }
+
+	@Override
+	public float rateMove(long move) {
+		return 0.0f;
+	}
+
+	@Override
+	public long heuristicMove(long legalMoves) {
+		return legalMoves;
+	}
 }

game/src/main/java/org/toop/game/players/ai/MCTSAI.java

@@ -1,193 +0,0 @@
-package org.toop.game.players.ai;
-
-import org.toop.framework.gameFramework.GameState;
-import org.toop.framework.gameFramework.model.game.PlayResult;
-import org.toop.framework.gameFramework.model.game.TurnBasedGame;
-import org.toop.framework.gameFramework.model.player.AbstractAI;
-
-import java.util.Random;
-
-public class MCTSAI<T extends TurnBasedGame<T>> extends AbstractAI<T> {
-	private static class Node {
-		public TurnBasedGame<?> state;
-		public long move;
-
-		public Node parent;
-
-		public int expanded;
-		public Node[] children;
-
-		public int visits;
-		public float value;
-
-		public Node(TurnBasedGame<?> state, long move, Node parent) {
-			this.state = state;
-			this.move = move;
-
-			this.parent = parent;
-
-			this.expanded = 0;
-			this.children = new Node[Long.bitCount(state.getLegalMoves())];
-
-			this.visits = 0;
-			this.value = 0.0f;
-		}
-
-		public Node(TurnBasedGame<?> state) {
-			this(state, 0L, null);
-		}
-
-		public boolean isFullyExpanded() {
-			return expanded >= children.length;
-		}
-
-		float calculateUCT() {
-			float exploitation = visits <= 0? 0 : value / visits;
-			float exploration = 1.41f * (float)(Math.sqrt(Math.log(visits) / visits));
-
-			return exploitation + exploration;
-		}
-
-		public Node bestUCTChild() {
-			int bestChildIndex = -1;
-			float bestScore = Float.NEGATIVE_INFINITY;
-
-			for (int i = 0; i < expanded; i++) {
-				final float score = calculateUCT();
-
-				if (score > bestScore) {
-					bestChildIndex = i;
-					bestScore = score;
-				}
-			}
-
-			return bestChildIndex >= 0? children[bestChildIndex] : this;
-		}
-	}
-
-	private final int milliseconds;
-
-	public MCTSAI(int milliseconds) {
-		this.milliseconds = milliseconds;
-	}
-
-	public MCTSAI(MCTSAI<T> other) {
-		this.milliseconds = other.milliseconds;
-	}
-
-	@Override
-	public MCTSAI<T> deepCopy() {
-		return new MCTSAI<>(this);
-	}
-
-	@Override
-	public long getMove(T game) {
-		Node root = new Node(game.deepCopy());
-
-		long endTime = System.currentTimeMillis() + milliseconds;
-
-		while (System.currentTimeMillis() <= endTime) {
-			Node node = selection(root);
-			long legalMoves = node.state.getLegalMoves();
-
-			if (legalMoves != 0) {
-				node = expansion(node, legalMoves);
-			}
-
-			float result = 0.0f;
-
-			if (node.state.getLegalMoves() != 0) {
-				result = simulation(node.state, game.getCurrentTurn());
-			}
-
-			backPropagation(node, result);
-		}
-
-		int mostVisitedIndex = -1;
-		int mostVisits = -1;
-
-		for (int i = 0; i < root.expanded; i++) {
-			if (root.children[i].visits > mostVisits) {
-				mostVisitedIndex = i;
-				mostVisits = root.children[i].visits;
-			}
-		}
-
-		return mostVisitedIndex != -1? root.children[mostVisitedIndex].move : randomSetBit(game.getLegalMoves());
-	}
-
-	private Node selection(Node node) {
-		while (node.state.getLegalMoves() != 0L && node.isFullyExpanded()) {
-			node = node.bestUCTChild();
-		}
-
-		return node;
-	}
-
-	private Node expansion(Node node, long legalMoves) {
-		for (int i = 0; i < node.expanded; i++) {
-			legalMoves &= ~node.children[i].move;
-		}
-
-		if (legalMoves == 0L) {
-			return node;
-		}
-
-		long move = randomSetBit(legalMoves);
-
-		TurnBasedGame<?> copy = node.state.deepCopy();
-		copy.play(move);
-
-		Node newlyExpanded = new Node(copy, move, node);
-
-		node.children[node.expanded] = newlyExpanded;
-		node.expanded++;
-
-		return newlyExpanded;
-	}
-
-	private float simulation(TurnBasedGame<?> state, int playerIndex) {
-		TurnBasedGame<?> copy = state.deepCopy();
-		long legalMoves = copy.getLegalMoves();
-		PlayResult result = null;
-
-		while (legalMoves != 0) {
-			result = copy.play(randomSetBit(legalMoves));
-			legalMoves = copy.getLegalMoves();
-		}
-
-		if (result.state() == GameState.WIN) {
-			if (result.player() == playerIndex) {
-				return 1.0f;
-			}
-
-			return -1.0f;
-		}
-
-		return -0.2f;
-	}
-
-	private void backPropagation(Node node, float value) {
-		while (node != null) {
-			node.visits++;
-			node.value += value;
-			node = node.parent;
-		}
-	}
-
-	public static long randomSetBit(long value) {
-		Random random = new Random();
-
-		int count = Long.bitCount(value);
-		int target = random.nextInt(count);
-
-		while (true) {
-			int bit = Long.numberOfTrailingZeros(value);
-			if (target == 0) {
-				return 1L << bit;
-			}
-			value &= value - 1;
-			target--;
-		}
-	}
-}

game/src/main/java/org/toop/game/players/ai/MCTSAI1.java

@@ -0,0 +1,250 @@
+package org.toop.game.players.ai;
+
+import org.toop.framework.gameFramework.model.game.TurnBasedGame;
+import org.toop.framework.gameFramework.model.player.AbstractAI;
+
+import java.util.Random;
+
+public class MCTSAI1<T extends TurnBasedGame<T>> extends AbstractAI<T> {
+	private static class Node {
+		public TurnBasedGame<?> state;
+
+		public long move;
+		public long unexpandedMoves;
+
+		public Node parent;
+
+		public Node[] children;
+		public int expanded;
+
+		public float value;
+		public int visits;
+
+		public boolean solved;
+		public float solvedValue;
+
+		public Node(TurnBasedGame<?> state, Node parent, long move) {
+			final long legalMoves = state.getLegalMoves();
+
+			this.state = state;
+
+			this.move = move;
+			this.unexpandedMoves = legalMoves;
+
+			this.parent = parent;
+
+			this.children = new Node[Long.bitCount(legalMoves)];
+			this.expanded = 0;
+
+			this.value = 0.0f;
+			this.visits = 0;
+
+			this.solved = false;
+			this.solvedValue = 0.0f;
+		}
+
+		public Node(TurnBasedGame<?> state) {
+			this(state, null, 0L);
+		}
+
+		public boolean isFullyExpanded() {
+			return expanded == children.length;
+		}
+
+		public float calculateUCT(int parentVisits) {
+			if (visits == 0) {
+				return Float.POSITIVE_INFINITY;
+			}
+
+			final float exploitation = value / visits;
+			final float exploration = 1.41f * (float)(Math.sqrt(Math.log(parentVisits) / visits));
+
+			return exploitation + exploration;
+		}
+
+		public Node bestUCTChild() {
+			Node highestUCTChild = null;
+			float highestUCT = Float.NEGATIVE_INFINITY;
+
+			for (int i = 0; i < expanded; i++) {
+				final float childUCT = children[i].calculateUCT(visits);
+
+				if (childUCT > highestUCT) {
+					highestUCTChild = children[i];
+					highestUCT = childUCT;
+				}
+			}
+
+			return highestUCTChild;
+		}
+	}
+
+	private static final Random random = new Random();
+
+	private final int milliseconds;
+
+	public MCTSAI1(int milliseconds) {
+		this.milliseconds = milliseconds;
+	}
+
+	public MCTSAI1(MCTSAI1<T> other) {
+		this.milliseconds = other.milliseconds;
+	}
+
+	@Override
+	public MCTSAI1<T> deepCopy() {
+		return new MCTSAI1<>(this);
+	}
+
+	@Override
+	public long getMove(T game) {
+		final Node root = new Node(game, null, 0L);
+
+		final long endTime = System.nanoTime() + milliseconds * 1_000_000L;
+
+		while (System.nanoTime() < endTime) {
+			Node leaf = selection(root);
+			leaf = expansion(leaf);
+			final float value = simulation(leaf);
+			backPropagation(leaf, value);
+		}
+
+		final Node mostVisitedChild = mostVisitedChild(root);
+		return mostVisitedChild.move;
+	}
+
+	private Node mostVisitedChild(Node root) {
+		Node mostVisitedChild = null;
+		int mostVisited = -1;
+
+		for (int i = 0; i < root.expanded; i++) {
+			if (root.children[i].visits > mostVisited) {
+				mostVisitedChild = root.children[i];
+				mostVisited = root.children[i].visits;
+			}
+		}
+
+		return mostVisitedChild;
+	}
+
+	private Node selection(Node root) {
+		while (!root.solved && root.isFullyExpanded() && !root.state.isTerminal()) {
+			root = root.bestUCTChild();
+		}
+
+		return root;
+	}
+
+	private Node expansion(Node leaf) {
+		if (leaf.unexpandedMoves == 0L) {
+			return leaf;
+		}
+
+		final long unexpandedMove = leaf.unexpandedMoves & -leaf.unexpandedMoves;
+
+		final TurnBasedGame<?> copiedState = leaf.state.deepCopy();
+		copiedState.play(unexpandedMove);
+
+		final Node expandedChild = new Node(copiedState, leaf, unexpandedMove);
+
+		leaf.children[leaf.expanded] = expandedChild;
+		leaf.expanded++;
+
+		leaf.unexpandedMoves &= ~unexpandedMove;
+
+		return expandedChild;
+	}
+
+	private float simulation(Node leaf) {
+		final TurnBasedGame<?> copiedState = leaf.state.deepCopy();
+		final int playerIndex = 1 - copiedState.getCurrentTurn();
+
+		while (!copiedState.isTerminal()) {
+			final long legalMoves = copiedState.getLegalMoves();
+			final long randomMove = randomSetBit(legalMoves);
+
+			copiedState.play(randomMove);
+		}
+
+		if (copiedState.getWinner() == playerIndex) {
+			return 1.0f;
+		}
+
+		if (copiedState.getWinner() >= 0) {
+			return -1.0f;
+		}
+
+		return 0.0f;
+	}
+
+	private void backPropagation(Node leaf, float value) {
+		while (leaf != null) {
+			leaf.value += value;
+			leaf.visits++;
+
+			if (!leaf.solved) {
+				updateSolvedStatus(leaf);
+			}
+
+			value = -value;
+			leaf = leaf.parent;
+		}
+	}
+
+	private void updateSolvedStatus(Node node) {
+		if (node.state.isTerminal()) {
+			node.solved = true;
+
+			final int winner = node.state.getWinner();
+			final int mover = 1 - node.state.getCurrentTurn();
+
+			node.solvedValue = winner == mover? 1.0f : winner == -1? 0.0f : -1.0f;
+
+			return;
+		}
+
+		if (node.isFullyExpanded()) {
+			boolean allChildrenSolved = true;
+			boolean foundWinningMove = false;
+			boolean foundDrawMove = false;
+
+			for (final Node child : node.children) {
+				if (child.solved) {
+					if (child.solvedValue == -1.0f) {
+						foundWinningMove = true;
+						break;
+					}
+
+					if (child.solvedValue == 0.0f) {
+						foundDrawMove = true;
+					}
+				} else {
+					allChildrenSolved = false;
+				}
+			}
+
+			if (foundWinningMove) {
+				node.solved = true;
+				node.solvedValue = 1.0f;
+			} else if (allChildrenSolved) {
+				node.solved = true;
+				node.solvedValue = foundDrawMove? 0.0f : -1.0f;
+			}
+		}
+	}
+
+	private long randomSetBit(long value) {
+		if (0L == value) {
+			return 0;
+		}
+
+		final int bitCount = Long.bitCount(value);
+		final int randomBitCount = random.nextInt(bitCount);
+
+		for (int i = 0; i < randomBitCount; i++) {
+			value &= value - 1;
+		}
+
+		return value & -value;
+	}
+}

game/src/main/java/org/toop/game/players/ai/MCTSAI2.java

@@ -20,6 +20,9 @@ public class MCTSAI2<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 		public float value;
 		public int visits;
 
+		public boolean solved;
+		public float solvedValue;
+
 		public Node(TurnBasedGame<?> state, Node parent, long move) {
 			final long legalMoves = state.getLegalMoves();
 
@@ -35,6 +38,9 @@ public class MCTSAI2<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 
 			this.value = 0.0f;
 			this.visits = 0;
+
+			this.solved = false;
+			this.solvedValue = 0.0f;
 		}
 
 		public Node(TurnBasedGame<?> state) {
@@ -46,6 +52,10 @@ public class MCTSAI2<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 		}
 
 		public float calculateUCT(int parentVisits) {
+			if (visits == 0) {
+				return Float.POSITIVE_INFINITY;
+			}
+
 			final float exploitation = value / visits;
 			final float exploration = 1.41f * (float)(Math.sqrt(Math.log(parentVisits) / visits));
 
@@ -63,24 +73,28 @@ public class MCTSAI2<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 					highestUCTChild = children[i];
 					highestUCT = childUCT;
 				}
-
 			}
 
 			return highestUCTChild;
 		}
 	}
 
-	private final Random random;
+	private static final Random random = new Random();
+
 	private final int milliseconds;
 
+	private Node root;
+
 	public MCTSAI2(int milliseconds) {
-		this.random = new Random();
 		this.milliseconds = milliseconds;
+
+		this.root = null;
 	}
 
-	public MCTSAI2(MCTSAI2<?> other) {
-		this.random = other.random;
+	public MCTSAI2(MCTSAI2<T> other) {
 		this.milliseconds = other.milliseconds;
+
+		this.root = other.root;
 	}
 
 	@Override
@@ -90,7 +104,7 @@ public class MCTSAI2<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 
 	@Override
 	public long getMove(T game) {
-		final Node root = new Node(game, null, 0L);
+		root = findOrResetRoot(root, game);
 
 		final long endTime = System.nanoTime() + milliseconds * 1_000_000L;
 
@@ -102,8 +116,11 @@ public class MCTSAI2<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 		}
 
 		final Node mostVisitedChild = mostVisitedChild(root);
+		final long move = mostVisitedChild.move;
 
-		return mostVisitedChild != null? mostVisitedChild.move : 0L;
+		root = findChildByMove(root, move);
+
+		return move;
 	}
 
 	private Node mostVisitedChild(Node root) {
@@ -120,8 +137,51 @@ public class MCTSAI2<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 		return mostVisitedChild;
 	}
 
+	private Node findOrResetRoot(Node root, T game) {
+		if (root == null) {
+			return new Node(game.deepCopy());
+		}
+
+		if (areStatesEqual(root.state.getBoard(), game.getBoard())) {
+			return root;
+		}
+
+		for (int i = 0; i < root.expanded; i++) {
+			if (areStatesEqual(root.children[i].state.getBoard(), game.getBoard())) {
+				root.children[i].parent = null;
+				return root.children[i];
+			}
+		}
+
+		return new Node(game.deepCopy());
+	}
+
+	private Node findChildByMove(Node root, long move) {
+		for (int i = 0; i < root.expanded; i++) {
+			if (root.children[i].move == move) {
+				root.children[i].parent = null;
+				return root.children[i];
+			}
+		}
+
+		return null;
+	}
+
+	private boolean areStatesEqual(long[] state1, long[] state2) {
+		if (state1.length != state2.length) {
+			return false;
+		}
+
+		for (int i = 0; i < state1.length; i++) {
+			if (state1[i] != state2[i]) {
+				return false;
+			}
+		}
+
+		return true;
+	}
 	private Node selection(Node root) {
-		while (root.isFullyExpanded() && !root.state.isTerminal()) {
+		while (!root.solved && root.isFullyExpanded() && !root.state.isTerminal()) {
 			root = root.bestUCTChild();
 		}
 
@@ -161,7 +221,9 @@ public class MCTSAI2<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 
 		if (copiedState.getWinner() == playerIndex) {
 			return 1.0f;
-		} else if (copiedState.getWinner() >= 0) {
+		}
+
+		if (copiedState.getWinner() >= 0) {
 			return -1.0f;
 		}
 
@@ -173,11 +235,57 @@ public class MCTSAI2<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 			leaf.value += value;
 			leaf.visits++;
 
+			if (!leaf.solved) {
+				updateSolvedStatus(leaf);
+			}
+
 			value = -value;
 			leaf = leaf.parent;
 		}
 	}
 
+	private void updateSolvedStatus(Node node) {
+		if (node.state.isTerminal()) {
+			node.solved = true;
+
+			final int winner = node.state.getWinner();
+			final int mover = 1 - node.state.getCurrentTurn();
+
+			node.solvedValue = winner == mover? 1.0f : winner == -1? 0.0f : -1.0f;
+
+			return;
+		}
+
+		if (node.isFullyExpanded()) {
+			boolean allChildrenSolved = true;
+			boolean foundWinningMove = false;
+			boolean foundDrawMove = false;
+
+			for (final Node child : node.children) {
+				if (child.solved) {
+					if (child.solvedValue == -1.0f) {
+						foundWinningMove = true;
+						break;
+					}
+
+					if (child.solvedValue == 0.0f) {
+						foundDrawMove = true;
+					}
+				} else {
+					allChildrenSolved = false;
+				}
+			}
+
+			if (foundWinningMove) {
+				node.solved = true;
+				node.solvedValue = 1.0f;
+			} else if (allChildrenSolved) {
+				node.solved = true;
+				node.solvedValue = foundDrawMove? 0.0f : -1.0f;
+			}
+		}
+	}
+
 	private long randomSetBit(long value) {
 		if (0L == value) {
 			return 0;

game/src/main/java/org/toop/game/players/ai/MCTSAI3.java

@@ -3,7 +3,13 @@ package org.toop.game.players.ai;
 import org.toop.framework.gameFramework.model.game.TurnBasedGame;
 import org.toop.framework.gameFramework.model.player.AbstractAI;
 
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Random;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
 
 public class MCTSAI3<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 	private static class Node {
@@ -20,6 +26,9 @@ public class MCTSAI3<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 		public float value;
 		public int visits;
 
+		public boolean solved;
+		public float solvedValue;
+
 		public Node(TurnBasedGame<?> state, Node parent, long move) {
 			final long legalMoves = state.getLegalMoves();
 
@@ -35,6 +44,9 @@ public class MCTSAI3<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 
 			this.value = 0.0f;
 			this.visits = 0;
+
+			this.solved = false;
+			this.solvedValue = 0.0f;
 		}
 
 		public Node(TurnBasedGame<?> state) {
@@ -46,6 +58,10 @@ public class MCTSAI3<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 		}
 
 		public float calculateUCT(int parentVisits) {
+			if (visits == 0) {
+				return Float.POSITIVE_INFINITY;
+			}
+
 			final float exploitation = value / visits;
 			final float exploration = 1.41f * (float)(Math.sqrt(Math.log(parentVisits) / visits));
 
@@ -63,30 +79,25 @@ public class MCTSAI3<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 					highestUCTChild = children[i];
 					highestUCT = childUCT;
 				}
-
 			}
 
 			return highestUCTChild;
 		}
 	}
 
-	private final Random random;
+	private static final ThreadLocal<Random> random = ThreadLocal.withInitial(Random::new);
 
-	private Node root;
 	private final int milliseconds;
+	private final int threads;
 
-	public MCTSAI3(int milliseconds) {
-		this.random = new Random();
-
-		this.root = null;
+	public MCTSAI3(int milliseconds, int threads) {
 		this.milliseconds = milliseconds;
+		this.threads = threads;
 	}
 
-	public MCTSAI3(MCTSAI3<?> other) {
-		this.random = other.random;
-
-		this.root = other.root;
+	public MCTSAI3(MCTSAI3<T> other) {
 		this.milliseconds = other.milliseconds;
+		this.threads = other.threads;
 	}
 
 	@Override
@@ -96,23 +107,57 @@ public class MCTSAI3<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 
 	@Override
 	public long getMove(T game) {
-		detectRoot(game);
-
+		final ExecutorService pool = Executors.newFixedThreadPool(threads);
 		final long endTime = System.nanoTime() + milliseconds * 1_000_000L;
 
-		while (System.nanoTime() < endTime) {
-			Node leaf = selection(root);
-			leaf = expansion(leaf);
-			final float value = simulation(leaf);
-			backPropagation(leaf, value);
+		final List<Callable<Node>> tasks = new ArrayList<>();
+
+		for (int i = 0; i < threads; i++) {
+			tasks.add(() -> {
+				final Node localRoot = new Node(game.deepCopy());
+
+				while (System.nanoTime() < endTime) {
+					Node leaf = selection(localRoot);
+					leaf = expansion(leaf);
+					final float value = simulation(leaf);
+					backPropagation(leaf, value);
+				}
+
+				return localRoot;
+			});
 		}
 
-		final Node mostVisitedChild = mostVisitedChild(root);
-		final long move = mostVisitedChild != null? mostVisitedChild.move : 0L;
+		try {
+			final List<Future<Node>> results = pool.invokeAll(tasks);
 
-		newRoot(move);
+			pool.shutdown();
 
-		return move;
+			final Node root = new Node(game.deepCopy());
+
+			for (int i = 0; i < root.children.length; i++) {
+				expansion(root);
+			}
+
+			for (final Future<Node> result : results) {
+				final Node localRoot = result.get();
+
+				for (final Node localChild : localRoot.children) {
+					for (int i = 0; i < root.children.length; i++) {
+						if (localChild.move == root.children[i].move) {
+							root.children[i].visits += localChild.visits;
+							root.visits += localChild.visits;
+							break;
+						}
+					}
+				}
+			}
+
+			final Node mostVisitedChild = mostVisitedChild(root);
+			return mostVisitedChild.move;
+		} catch (Exception _) {
+			final long legalMoves = game.getLegalMoves();
+			return randomSetBit(legalMoves);
+		}
 	}
 
 	private Node mostVisitedChild(Node root) {
@@ -129,62 +174,8 @@ public class MCTSAI3<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 		return mostVisitedChild;
 	}
 
-	private void detectRoot(T game) {
-		if (root == null) {
-			root = new Node(game.deepCopy());
-			return;
-		}
-
-		final long[] currentBoards = game.getBoard();
-		final long[] rootBoards = root.state.getBoard();
-
-		boolean detected = true;
-
-		for (int i = 0; i < rootBoards.length; i++) {
-			if (rootBoards[i] != currentBoards[i]) {
-				detected = false;
-				break;
-			}
-		}
-
-		if (detected) {
-			return;
-		}
-
-		for (int i = 0; i < root.expanded; i++) {
-			final Node child = root.children[i];
-
-			final long[] childBoards = child.state.getBoard();
-
-			detected = true;
-
-			for (int j = 0; j < childBoards.length; j++) {
-				if (childBoards[j] != currentBoards[j]) {
-					detected = false;
-					break;
-				}
-			}
-
-			if (detected) {
-				root = child;
-				return;
-			}
-		}
-
-		root = new Node(game.deepCopy());
-	}
-
-	private void newRoot(long move) {
-		for (final Node child : root.children) {
-			if (child.move == move) {
-				root = child;
-				break;
-			}
-		}
-	}
-
 	private Node selection(Node root) {
-		while (root.isFullyExpanded() && !root.state.isTerminal()) {
+		while (!root.solved && root.isFullyExpanded() && !root.state.isTerminal()) {
 			root = root.bestUCTChild();
 		}
 
@@ -224,7 +215,9 @@ public class MCTSAI3<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 
 		if (copiedState.getWinner() == playerIndex) {
 			return 1.0f;
-		} else if (copiedState.getWinner() >= 0) {
+		}
+
+		if (copiedState.getWinner() >= 0) {
 			return -1.0f;
 		}
 
@@ -236,18 +229,64 @@ public class MCTSAI3<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 			leaf.value += value;
 			leaf.visits++;
 
+			if (!leaf.solved) {
+				updateSolvedStatus(leaf);
+			}
+
 			value = -value;
 			leaf = leaf.parent;
 		}
 	}
 
+	private void updateSolvedStatus(Node node) {
+		if (node.state.isTerminal()) {
+			node.solved = true;
+
+			final int winner = node.state.getWinner();
+			final int mover = 1 - node.state.getCurrentTurn();
+
+			node.solvedValue = winner == mover? 1.0f : winner == -1? 0.0f : -1.0f;
+
+			return;
+		}
+
+		if (node.isFullyExpanded()) {
+			boolean allChildrenSolved = true;
+			boolean foundWinningMove = false;
+			boolean foundDrawMove = false;
+
+			for (final Node child : node.children) {
+				if (child.solved) {
+					if (child.solvedValue == -1.0f) {
+						foundWinningMove = true;
+						break;
+					}
+
+					if (child.solvedValue == 0.0f) {
+						foundDrawMove = true;
+					}
+				} else {
+					allChildrenSolved = false;
+				}
+			}
+
+			if (foundWinningMove) {
+				node.solved = true;
+				node.solvedValue = 1.0f;
+			} else if (allChildrenSolved) {
+				node.solved = true;
+				node.solvedValue = foundDrawMove? 0.0f : -1.0f;
+			}
+		}
+	}
+
 	private long randomSetBit(long value) {
 		if (0L == value) {
 			return 0;
 		}
 
 		final int bitCount = Long.bitCount(value);
-		final int randomBitCount = random.nextInt(bitCount);
+		final int randomBitCount = random.get().nextInt(bitCount);
 
 		for (int i = 0; i < randomBitCount; i++) {
 			value &= value - 1;
@@ -255,4 +294,4 @@ public class MCTSAI3<T extends TurnBasedGame<T>> extends AbstractAI<T> {
 
 		return value & -value;
 	}
-}
+}

game/src/main/java/org/toop/game/players/ai/MCTSAI4.java

@@ -0,0 +1,359 @@
+package org.toop.game.players.ai;
+
+import org.toop.framework.gameFramework.model.game.TurnBasedGame;
+import org.toop.framework.gameFramework.model.player.AbstractAI;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+public class MCTSAI4<T extends TurnBasedGame<T>> extends AbstractAI<T> {
+	private static class Node {
+		public TurnBasedGame<?> state;
+
+		public long move;
+		public long unexpandedMoves;
+
+		public Node parent;
+
+		public Node[] children;
+		public int expanded;
+
+		public float value;
+		public int visits;
+
+		public boolean solved;
+		public float solvedValue;
+
+		public Node(TurnBasedGame<?> state, Node parent, long move) {
+			final long legalMoves = state.getLegalMoves();
+
+			this.state = state;
+
+			this.move = move;
+			this.unexpandedMoves = legalMoves;
+
+			this.parent = parent;
+
+			this.children = new Node[Long.bitCount(legalMoves)];
+			this.expanded = 0;
+
+			this.value = 0.0f;
+			this.visits = 0;
+
+			this.solved = false;
+			this.solvedValue = 0.0f;
+		}
+
+		public Node(TurnBasedGame<?> state) {
+			this(state, null, 0L);
+		}
+
+		public boolean isFullyExpanded() {
+			return expanded == children.length;
+		}
+
+		public float calculateUCT(int parentVisits) {
+			if (visits == 0) {
+				return Float.POSITIVE_INFINITY;
+			}
+
+			final float exploitation = value / visits;
+			final float exploration = 1.41f * (float)(Math.sqrt(Math.log(parentVisits) / visits));
+
+			return exploitation + exploration;
+		}
+
+		public Node bestUCTChild() {
+			Node highestUCTChild = null;
+			float highestUCT = Float.NEGATIVE_INFINITY;
+
+			for (int i = 0; i < expanded; i++) {
+				final float childUCT = children[i].calculateUCT(visits);
+
+				if (childUCT > highestUCT) {
+					highestUCTChild = children[i];
+					highestUCT = childUCT;
+				}
+			}
+
+			return highestUCTChild;
+		}
+	}
+
+	private static final ThreadLocal<Random> random = ThreadLocal.withInitial(Random::new);
+
+	private final int milliseconds;
+	private final int threads;
+
+	private final Node[] threadRoots;
+
+	public MCTSAI4(int milliseconds, int threads) {
+		this.milliseconds = milliseconds;
+		this.threads = threads;
+
+		this.threadRoots = new Node[threads];
+	}
+
+	public MCTSAI4(MCTSAI4<T> other) {
+		this.milliseconds = other.milliseconds;
+		this.threads = other.threads;
+
+		this.threadRoots = other.threadRoots;
+	}
+
+	@Override
+	public MCTSAI4<T> deepCopy() {
+		return new MCTSAI4<>(this);
+	}
+
+	@Override
+	public long getMove(T game) {
+		for (int i = 0; i < threads; i++) {
+			threadRoots[i] = findOrResetRoot(threadRoots[i], game);
+		}
+
+		final ExecutorService pool = Executors.newFixedThreadPool(threads);
+		final long endTime = System.nanoTime() + milliseconds * 1_000_000L;
+
+		final List<Callable<Node>> tasks = new ArrayList<>();
+
+		for (int i = 0; i < threads; i++) {
+			final int threadIndex = i;
+
+			tasks.add(() -> {
+				final Node localRoot = threadRoots[threadIndex];
+
+				while (System.nanoTime() < endTime) {
+					Node leaf = selection(localRoot);
+					leaf = expansion(leaf);
+					final float value = simulation(leaf);
+					backPropagation(leaf, value);
+				}
+
+				return localRoot;
+			});
+		}
+
+		try {
+			final List<Future<Node>> results = pool.invokeAll(tasks);
+
+			pool.shutdown();
+
+			final Node root = new Node(game.deepCopy());
+
+			for (int i = 0; i < root.children.length; i++) {
+				expansion(root);
+			}
+
+			for (final Future<Node> result : results) {
+				final Node localRoot = result.get();
+
+				for (final Node localChild : localRoot.children) {
+					for (int i = 0; i < root.children.length; i++) {
+						if (localChild.move == root.children[i].move) {
+							root.children[i].visits += localChild.visits;
+							root.visits += localChild.visits;
+							break;
+						}
+					}
+				}
+			}
+
+			final Node mostVisitedChild = mostVisitedChild(root);
+			final long move = mostVisitedChild.move;
+
+			for (int i = 0; i < threads; i++) {
+				threadRoots[i] = findChildByMove(threadRoots[i], move);
+			}
+
+			return move;
+		} catch (Exception _) {
+			final long legalMoves = game.getLegalMoves();
+			return randomSetBit(legalMoves);
+		}
+	}
+
+	private Node mostVisitedChild(Node root) {
+		Node mostVisitedChild = null;
+		int mostVisited = -1;
+
+		for (int i = 0; i < root.expanded; i++) {
+			if (root.children[i].visits > mostVisited) {
+				mostVisitedChild = root.children[i];
+				mostVisited = root.children[i].visits;
+			}
+		}
+
+		return mostVisitedChild;
+	}
+
+	private Node findOrResetRoot(Node root, T game) {
+		if (root == null) {
+			return new Node(game.deepCopy());
+		}
+
+		if (areStatesEqual(root.state.getBoard(), game.getBoard())) {
+			return root;
+		}
+
+		for (int i = 0; i < root.expanded; i++) {
+			if (areStatesEqual(root.children[i].state.getBoard(), game.getBoard())) {
+				root.children[i].parent = null;
+				return root.children[i];
+			}
+		}
+
+		return new Node(game.deepCopy());
+	}
+
+	private Node findChildByMove(Node root, long move) {
+		for (int i = 0; i < root.expanded; i++) {
+			if (root.children[i].move == move) {
+				root.children[i].parent = null;
+				return root.children[i];
+			}
+		}
+
+		return null;
+	}
+
+	private boolean areStatesEqual(long[] state1, long[] state2) {
+		if (state1.length != state2.length) {
+			return false;
+		}
+
+		for (int i = 0; i < state1.length; i++) {
+			if (state1[i] != state2[i]) {
+				return false;
+			}
+		}
+
+		return true;
+	}
+
+	private Node selection(Node root) {
+		while (!root.solved && root.isFullyExpanded() && !root.state.isTerminal()) {
+			root = root.bestUCTChild();
+		}
+
+		return root;
+	}
+
+	private Node expansion(Node leaf) {
+		if (leaf.unexpandedMoves == 0L) {
+			return leaf;
+		}
+
+		final long unexpandedMove = leaf.unexpandedMoves & -leaf.unexpandedMoves;
+
+		final TurnBasedGame<?> copiedState = leaf.state.deepCopy();
+		copiedState.play(unexpandedMove);
+
+		final Node expandedChild = new Node(copiedState, leaf, unexpandedMove);
+
+		leaf.children[leaf.expanded] = expandedChild;
+		leaf.expanded++;
+
+		leaf.unexpandedMoves &= ~unexpandedMove;
+
+		return expandedChild;
+	}
+
+	private float simulation(Node leaf) {
+		final TurnBasedGame<?> copiedState = leaf.state.deepCopy();
+		final int playerIndex = 1 - copiedState.getCurrentTurn();
+
+		while (!copiedState.isTerminal()) {
+			final long legalMoves = copiedState.getLegalMoves();
+			final long randomMove = randomSetBit(legalMoves);
+
+			copiedState.play(randomMove);
+		}
+
+		if (copiedState.getWinner() == playerIndex) {
+			return 1.0f;
+		}
+
+		if (copiedState.getWinner() >= 0) {
+			return -1.0f;
+		}
+
+		return 0.0f;
+	}
+
+	private void backPropagation(Node leaf, float value) {
+		while (leaf != null) {
+			leaf.value += value;
+			leaf.visits++;
+
+			if (!leaf.solved) {
+				updateSolvedStatus(leaf);
+			}
+
+			value = -value;
+			leaf = leaf.parent;
+		}
+	}
+
+	private void updateSolvedStatus(Node node) {
+		if (node.state.isTerminal()) {
+			node.solved = true;
+
+			final int winner = node.state.getWinner();
+			final int mover = 1 - node.state.getCurrentTurn();
+
+			node.solvedValue = winner == mover? 1.0f : winner == -1? 0.0f : -1.0f;
+
+			return;
+		}
+
+		if (node.isFullyExpanded()) {
+			boolean allChildrenSolved = true;
+			boolean foundWinningMove = false;
+			boolean foundDrawMove = false;
+
+			for (final Node child : node.children) {
+				if (child.solved) {
+					if (child.solvedValue == -1.0f) {
+						foundWinningMove = true;
+						break;
+					}
+
+					if (child.solvedValue == 0.0f) {
+						foundDrawMove = true;
+					}
+				} else {
+					allChildrenSolved = false;
+				}
+			}
+
+			if (foundWinningMove) {
+				node.solved = true;
+				node.solvedValue = 1.0f;
+			} else if (allChildrenSolved) {
+				node.solved = true;
+				node.solvedValue = foundDrawMove? 0.0f : -1.0f;
+			}
+		}
+	}
+
+	private long randomSetBit(long value) {
+		if (0L == value) {
+			return 0;
+		}
+
+		final int bitCount = Long.bitCount(value);
+		final int randomBitCount = random.get().nextInt(bitCount);
+
+		for (int i = 0; i < randomBitCount; i++) {
+			value &= value - 1;
+		}
+
+		return value & -value;
+	}
+}

game/src/main/java/org/toop/game/players/ai/MCTSAI5.java

@@ -0,0 +1,371 @@
+package org.toop.game.players.ai;
+
+import org.toop.framework.gameFramework.model.game.TurnBasedGame;
+import org.toop.framework.gameFramework.model.player.AbstractAI;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+public class MCTSAI5<T extends TurnBasedGame<T>> extends AbstractAI<T> {
+	private static class Node {
+		public TurnBasedGame<?> state;
+
+		public long move;
+		public long unexpandedMoves;
+
+		public Node parent;
+
+		public Node[] children;
+		public int expanded;
+
+		public float value;
+		public int visits;
+
+		public boolean solved;
+		public float solvedValue;
+
+		public float heuristic;
+
+		public Node(TurnBasedGame<?> state, Node parent, long move) {
+			final long legalMoves = state.getLegalMoves();
+
+			this.state = state;
+
+			this.move = move;
+			this.unexpandedMoves = legalMoves;
+
+			this.parent = parent;
+
+			this.children = new Node[Long.bitCount(legalMoves)];
+			this.expanded = 0;
+
+			this.value = 0.0f;
+			this.visits = 0;
+
+			this.solved = false;
+			this.solvedValue = 0.0f;
+
+			this.heuristic = state.rateMove(move);
+		}
+
+		public Node(TurnBasedGame<?> state) {
+			this(state, null, 0L);
+		}
+
+		public boolean isFullyExpanded() {
+			return expanded == children.length;
+		}
+
+		public float calculateUCT(int parentVisits) {
+			if (visits == 0) {
+				return Float.POSITIVE_INFINITY;
+			}
+
+			final float exploitation = value / visits;
+			final float exploration = 1.41f * (float)(Math.sqrt(Math.log(parentVisits) / visits));
+			final float bias = heuristic / visits;
+
+			return exploitation + exploration + bias;
+		}
+
+		public Node bestUCTChild() {
+			Node highestUCTChild = null;
+			float highestUCT = Float.NEGATIVE_INFINITY;
+
+			for (int i = 0; i < expanded; i++) {
+				final float childUCT = children[i].calculateUCT(visits);
+
+				if (childUCT > highestUCT) {
+					highestUCTChild = children[i];
+					highestUCT = childUCT;
+				}
+			}
+
+			return highestUCTChild;
+		}
+	}
+
+	private static final ThreadLocal<Random> random = ThreadLocal.withInitial(Random::new);
+
+	private final int milliseconds;
+	private final int threads;
+
+	private final Node[] threadRoots;
+
+	public MCTSAI5(int milliseconds, int threads) {
+		this.milliseconds = milliseconds;
+		this.threads = threads;
+
+		this.threadRoots = new Node[threads];
+	}
+
+	public MCTSAI5(MCTSAI5<T> other) {
+		this.milliseconds = other.milliseconds;
+		this.threads = other.threads;
+
+		this.threadRoots = other.threadRoots;
+	}
+
+	@Override
+	public MCTSAI5<T> deepCopy() {
+		return new MCTSAI5<>(this);
+	}
+
+	@Override
+	public long getMove(T game) {
+		for (int i = 0; i < threads; i++) {
+			threadRoots[i] = findOrResetRoot(threadRoots[i], game);
+		}
+
+		final ExecutorService pool = Executors.newFixedThreadPool(threads);
+		final long endTime = System.nanoTime() + milliseconds * 1_000_000L;
+
+		final List<Callable<Node>> tasks = new ArrayList<>();
+
+		for (int i = 0; i < threads; i++) {
+			final int threadIndex = i;
+
+			tasks.add(() -> {
+				final Node localRoot = threadRoots[threadIndex];
+
+				while (System.nanoTime() < endTime) {
+					Node leaf = selection(localRoot);
+					leaf = expansion(leaf);
+					final float value = simulation(leaf);
+					backPropagation(leaf, value);
+				}
+
+				return localRoot;
+			});
+		}
+
+		try {
+			final List<Future<Node>> results = pool.invokeAll(tasks);
+
+			pool.shutdown();
+
+			final Node root = new Node(game.deepCopy());
+
+			for (int i = 0; i < root.children.length; i++) {
+				expansion(root);
+			}
+
+			for (final Future<Node> result : results) {
+				final Node localRoot = result.get();
+
+				for (final Node localChild : localRoot.children) {
+					for (int i = 0; i < root.children.length; i++) {
+						if (localChild.move == root.children[i].move) {
+							root.children[i].visits += localChild.visits;
+							root.visits += localChild.visits;
+							break;
+						}
+					}
+				}
+			}
+
+			final Node mostVisitedChild = mostVisitedChild(root);
+			final long move = mostVisitedChild.move;
+
+			for (int i = 0; i < threads; i++) {
+				threadRoots[i] = findChildByMove(threadRoots[i], move);
+			}
+
+			return move;
+		} catch (Exception _) {
+			final long legalMoves = game.getLegalMoves();
+			return randomSetBit(legalMoves);
+		}
+	}
+
+	private Node mostVisitedChild(Node root) {
+		Node mostVisitedChild = null;
+		int mostVisited = -1;
+
+		for (int i = 0; i < root.expanded; i++) {
+			if (root.children[i].visits > mostVisited) {
+				mostVisitedChild = root.children[i];
+				mostVisited = root.children[i].visits;
+			}
+		}
+
+		return mostVisitedChild;
+	}
+
+	private Node findOrResetRoot(Node root, T game) {
+		if (root == null) {
+			return new Node(game.deepCopy());
+		}
+
+		if (areStatesEqual(root.state.getBoard(), game.getBoard())) {
+			return root;
+		}
+
+		for (int i = 0; i < root.expanded; i++) {
+			if (areStatesEqual(root.children[i].state.getBoard(), game.getBoard())) {
+				root.children[i].parent = null;
+				return root.children[i];
+			}
+		}
+
+		return new Node(game.deepCopy());
+	}
+
+	private Node findChildByMove(Node root, long move) {
+		for (int i = 0; i < root.expanded; i++) {
+			if (root.children[i].move == move) {
+				root.children[i].parent = null;
+				return root.children[i];
+			}
+		}
+
+		return null;
+	}
+
+	private boolean areStatesEqual(long[] state1, long[] state2) {
+		if (state1.length != state2.length) {
+			return false;
+		}
+
+		for (int i = 0; i < state1.length; i++) {
+			if (state1[i] != state2[i]) {
+				return false;
+			}
+		}
+
+		return true;
+	}
+
+	private Node selection(Node root) {
+		while (!root.solved && root.isFullyExpanded() && !root.state.isTerminal()) {
+			root = root.bestUCTChild();
+		}
+
+		return root;
+	}
+
+	private Node expansion(Node leaf) {
+		if (leaf.unexpandedMoves == 0L) {
+			return leaf;
+		}
+
+		final long unexpandedMove = leaf.unexpandedMoves & -leaf.unexpandedMoves;
+
+		final TurnBasedGame<?> copiedState = leaf.state.deepCopy();
+		copiedState.play(unexpandedMove);
+
+		final Node expandedChild = new Node(copiedState, leaf, unexpandedMove);
+
+		leaf.children[leaf.expanded] = expandedChild;
+		leaf.expanded++;
+
+		leaf.unexpandedMoves &= ~unexpandedMove;
+
+		return expandedChild;
+	}
+
+	private float simulation(Node leaf) {
+		final TurnBasedGame<?> copiedState = leaf.state.deepCopy();
+		final int playerIndex = 1 - copiedState.getCurrentTurn();
+
+		while (!copiedState.isTerminal()) {
+			final long legalMoves = copiedState.getLegalMoves();
+
+			long move = 0L;
+
+			if (random.get().nextFloat() > 0.9f) {
+				move = copiedState.heuristicMove(legalMoves);
+			} else {
+				move = randomSetBit(legalMoves);
+			}
+
+			copiedState.play(move);
+		}
+
+		if (copiedState.getWinner() == playerIndex) {
+			return 1.0f;
+		}
+
+		if (copiedState.getWinner() >= 0) {
+			return -1.0f;
+		}
+
+		return 0.0f;
+	}
+
+	private void backPropagation(Node leaf, float value) {
+		while (leaf != null) {
+			leaf.value += value;
+			leaf.visits++;
+
+			if (!leaf.solved) {
+				updateSolvedStatus(leaf);
+			}
+
+			value = -value;
+			leaf = leaf.parent;
+		}
+	}
+
+	private void updateSolvedStatus(Node node) {
+		if (node.state.isTerminal()) {
+			node.solved = true;
+
+			final int winner = node.state.getWinner();
+			final int mover = 1 - node.state.getCurrentTurn();
+
+			node.solvedValue = winner == mover? 1.0f : winner == -1? 0.0f : -1.0f;
+
+			return;
+		}
+
+		if (node.isFullyExpanded()) {
+			boolean allChildrenSolved = true;
+			boolean foundWinningMove = false;
+			boolean foundDrawMove = false;
+
+			for (final Node child : node.children) {
+				if (child.solved) {
+					if (child.solvedValue == -1.0f) {
+						foundWinningMove = true;
+						break;
+					}
+
+					if (child.solvedValue == 0.0f) {
+						foundDrawMove = true;
+					}
+				} else {
+					allChildrenSolved = false;
+				}
+			}
+
+			if (foundWinningMove) {
+				node.solved = true;
+				node.solvedValue = 1.0f;
+			} else if (allChildrenSolved) {
+				node.solved = true;
+				node.solvedValue = foundDrawMove? 0.0f : -1.0f;
+			}
+		}
+	}
+
+	private long randomSetBit(long value) {
+		if (0L == value) {
+			return 0;
+		}
+
+		final int bitCount = Long.bitCount(value);
+		final int randomBitCount = random.get().nextInt(bitCount);
+
+		for (int i = 0; i < randomBitCount; i++) {
+			value &= value - 1;
+		}
+
+		return value & -value;
+	}
+}