Substantially improved performance of Board.isLegal().

No longer a static method.
AlphaBeta is now playable with 4-move lookahead (although slow).

src/model/Board.java

@@ -12,14 +12,20 @@ public class Board {
 	public static final int NUM_ROWS = 5;
 	public static final int ROW_REMOVAL_SIZE = 3;
 
-	public static boolean isLegal(Board brd, CellPointer cp) {
+	private boolean boardEmpty = true;
+	
+	public boolean isLegal(CellPointer cp) {
+		//coordinates are out of board bounds
 		if (cp.r < 0 || cp.r >= Board.NUM_ROWS || cp.c < 0
 				|| cp.c >= Board.NUM_COLS) {
 			return false;
 		}
 
-		boolean legal = (brd.getTile(cp.r, cp.c) == TileColor.NONE);
+		//target coordinate already has a tile
-
+		if (board[cp.r][cp.c] != TileColor.NONE) {
+			return false;
+		}
+		
 		boolean rowUp = (cp.r - 1) >= 0;
 		boolean rowDown = (cp.r + 1) < Board.NUM_ROWS;
 		boolean colUp = (cp.c - 1) >= 0;
@@ -27,49 +33,49 @@ public class Board {
 
 		// r-1 / c-1
 		if (rowUp && colUp
-				&& (brd.getTile(cp.r - 1, cp.c - 1) != TileColor.NONE)) {
+				&& (board[cp.r - 1][ cp.c - 1] != TileColor.NONE)) {
-			return legal && true;
+			return true;
 		}
 
 		// r-1 / c
-		if (rowUp && (brd.getTile(cp.r - 1, cp.c) != TileColor.NONE)) {
+		if (rowUp && (board[cp.r - 1][ cp.c] != TileColor.NONE)) {
-			return legal && true;
+			return true;
 		}
 
 		// r-1 / c+1
 		if (rowUp && colDown
-				&& (brd.getTile(cp.r - 1, cp.c + 1) != TileColor.NONE)) {
+				&& (board[cp.r - 1][ cp.c + 1] != TileColor.NONE)) {
-			return legal && true;
+			return true;
 		}
 
 		// r / c-1
-		if (colUp && (brd.getTile(cp.r, cp.c - 1) != TileColor.NONE)) {
+		if (colUp && (board[cp.r][ cp.c - 1] != TileColor.NONE)) {
-			return legal && true;
+			return true;
 		}
 
 		// r / c+1
-		if (colDown && (brd.getTile(cp.r, cp.c + 1) != TileColor.NONE)) {
+		if (colDown && (board[cp.r][ cp.c + 1] != TileColor.NONE)) {
-			return legal && true;
+			return true;
 		}
 
 		// r+1 / c-1
 		if (rowDown && colUp
-				&& (brd.getTile(cp.r + 1, cp.c - 1) != TileColor.NONE)) {
+				&& (board[cp.r + 1][ cp.c - 1] != TileColor.NONE)) {
-			return legal && true;
+			return true;
 		}
 
 		// r+1 / c
-		if (rowDown && (brd.getTile(cp.r + 1, cp.c) != TileColor.NONE)) {
+		if (rowDown && (board[cp.r + 1][ cp.c] != TileColor.NONE)) {
-			return legal && true;
+			return true;
 		}
 
 		// r+1 / c+1
 		if (rowDown && colDown
-				&& (brd.getTile(cp.r + 1, cp.c + 1) != TileColor.NONE)) {
+				&& (board[cp.r + 1][ cp.c + 1] != TileColor.NONE)) {
-			return legal && true;
+			return true;
 		}
 
-		return brd.isEmpty();
+		return boardEmpty;
 	}
 
 	private final TileColor[][] board;
@@ -91,6 +97,7 @@ public class Board {
 
 		for (int r = 0; r < NUM_ROWS; r++) {
 			for (int c = 0; c < NUM_COLS; c++) {
+				this.boardEmpty = that.boardEmpty;
 				this.board[r][c] = that.board[r][c];
 			}
 		}
@@ -163,7 +170,7 @@ public class Board {
 	}
 
 	public boolean playTile(CellPointer cp, TileColor tile) {
-		if (!isLegal(this, cp)) {
+		if (!isLegal(cp)) {
 			return false; // Illegal move.
 		}
 
@@ -304,6 +311,8 @@ public class Board {
 		}
 
 		numPlies++;
+		
+		boardEmpty = false;
 		return true;
 	}
 
@@ -320,16 +329,4 @@ public class Board {
 		}
 		return sb1.toString();
 	}
-
-	private boolean isEmpty() {
-		for (int r = 0; r < Board.NUM_ROWS; r++) {
-			for (int c = 0; c < Board.NUM_COLS; c++) {
-				if (getTile(r, c) != TileColor.NONE) {
-					return false;
-				}
-			}
-		}
-
-		return true;
-	}
 }

src/model/comPlayer/CountingPlayer.java

@@ -286,7 +286,7 @@ public class CountingPlayer implements Player {
 
 		for (int r = 0; r < Board.NUM_ROWS; r++) {
 			for (int c = 0; c < Board.NUM_COLS; c++) {
-				if (Board.isLegal(board, new CellPointer(r, c))) {
+				if (board.isLegal(new CellPointer(r, c))) {
 					moves.add(new Move(TileColor.BLUE, r, c));
 					moves.add(new Move(TileColor.GREEN, r, c));
 					moves.add(new Move(TileColor.RED, r, c));

src/model/comPlayer/generator/NeuralNetworkMoveGenerator.java

@@ -80,7 +80,7 @@ public class NeuralNetworkMoveGenerator implements MoveGenerator {
 			}
 		}
 
-		while (!Board.isLegal(board, mv.getCell())) {
+		while (!board.isLegal(mv.getCell())) {
 			mv = new Move(mv.getColor(), new CellPointer(
 					PlayerModel.rand.nextInt(Board.NUM_ROWS),
 					PlayerModel.rand.nextInt(Board.NUM_COLS)));

src/model/comPlayer/generator/ValidMoveGenerator.java

@@ -22,13 +22,11 @@ public class ValidMoveGenerator implements MoveGenerator {
 
 		for (int r = 0; r < Board.NUM_ROWS; r++) {
 			for (int c = 0; c < Board.NUM_COLS; c++) {
-				if (Board.isLegal(board, new CellPointer(r, c))) {
+				if (board.isLegal(new CellPointer(r, c))) {
-					for (TileColor color : TileColor.values()) {
+					validMoves.add(new Move(TileColor.BLUE, r, c));
-						if (color == TileColor.NONE) {
+					validMoves.add(new Move(TileColor.GREEN, r, c));
-							continue;
+					validMoves.add(new Move(TileColor.RED, r, c));
-						}
+					validMoves.add(new Move(TileColor.YELLOW, r, c));
-						validMoves.add(new Move(color, r, c));
-					}
 				}
 			}
 		}