Checking draw by repetition. Improved time management.

src/main/java/se/dykstrom/ronja/common/model/Game.java

@@ -55,11 +55,17 @@ public class Game {
     /** Index to keep track of the number of stored moves. */
     private int moveIndex;
 
+    /** All historic positions in this game. */
+    public final Position[] positions = new Position[MAX_MOVES];
+
+    /** Index to keep track of the number of stored positions. */
+    public int positionIndex;
+
     /** The name of the opponent as set by the "name" command.*/
     private String opponent;
 
     /** A reference to the opening book used in this game. */
-    private OpeningBook book;
+    private final OpeningBook book;
 
     /** The game result, or {@code null} if the game has not yet ended. */
     private String result;
@@ -82,12 +88,6 @@ public class Game {
     /** Remaining time and moves for the engine. */
     private TimeData timeData;
 
-    /** All historic positions in this game. */
-    private final Position[] positions = new Position[MAX_MOVES];
-
-    /** Index to keep track of the number of stored positions. */
-    private int positionIndex;
-
     // ------------------------------------------------------------------------
 
     /**
@@ -211,13 +211,6 @@ public String getOpponent() {
         return opponent;
     }
 
-    /**
-     * Returns the list of historical positions.
-     */
-    public Position[] getPositions() {
-        return positions;
-    }
-
     /**
      * Sets the current position and the start position of the game to the given position.
      * Also resets the lists of historical positions and moves.

src/main/java/se/dykstrom/ronja/common/model/Position.java

@@ -726,6 +726,26 @@ public boolean equals(Object obj) {
         }
     }
 
+    /**
+     * Returns {@code true} if this position is equal to the given position if the full move number
+     * and half move clock are ignored.
+     *
+     * @param other The other position to compare with.
+     * @return True if the positions are equal.
+     */
+    public boolean equalTo(Position other) {
+        return ((flags == other.flags) &&
+                (enPassantSquare == other.enPassantSquare) &&
+                (white == other.white) &&
+                (black == other.black) &&
+                (bishop == other.bishop) &&
+                (king == other.king) &&
+                (knight == other.knight) &&
+                (pawn == other.pawn) &&
+                (queen == other.queen) &&
+                (rook == other.rook));
+    }
+
     @Override
     public String toString() {
         StringBuilder[] ranks = new StringBuilder[8];

src/main/java/se/dykstrom/ronja/engine/core/AlphaBetaFinder.java

@@ -202,7 +202,7 @@ int alphaBeta(Position position, int lastMove, int depth, int alpha, int beta) {
             if (DEBUG) TLOG.finest(leave(position, depth) + ", score = " + Evaluator.CHECK_MATE_VALUE);
             return Evaluator.CHECK_MATE_VALUE;
         }
-        if (PositionUtils.isDraw(position)) {
+        if (PositionUtils.isDraw(position, game)) {
             if (DEBUG) TLOG.finest(leave(position, depth) + ", score = " + Evaluator.DRAW_VALUE);
             return Evaluator.DRAW_VALUE;
         }

src/main/java/se/dykstrom/ronja/engine/time/TimeUtils.java

@@ -127,13 +127,21 @@ private static long getMinutesAsMillis(Matcher matcher) {
     public static long calculateTimeForNextMove(TimeControl timeControl, TimeData timeData) {
         if (timeControl.getType() == TimeControlType.SECONDS_PER_MOVE) {
             // Use all available time minus a safety margin
-            return timeData.getRemainingTime() - 50;
+            // The safety margin is 10% of the time up to 500 ms
+            long margin = Math.min(timeData.getRemainingTime() / 10, 500);
+            return timeData.getRemainingTime() - margin;
         } else if (timeControl.getType() == TimeControlType.CLASSIC) {
-            // Divide remaining time evenly between remaining moves
-            return timeData.getRemainingTime() / timeData.getNumberOfMoves();
+            // Divide the remaining time between remaining moves,
+            // but allocate more time to moves early in the game
+            double partOfMovesLeft = 1.0 * timeData.getNumberOfMoves() / timeControl.getNumberOfMoves();
+            double factor = 0.6 * partOfMovesLeft + 0.7;
+            long evenlyDividedTime = timeData.getRemainingTime() / timeData.getNumberOfMoves();
+            return (long) (evenlyDividedTime * factor);
         } else { // TimeControlType.INCREMENTAL
-            // Always assume there are 20 moves left
-            return timeData.getRemainingTime() / 20;
+            // Remove increment that was added after last move to get remaining base time
+            long baseTime = timeData.getRemainingTime() - timeControl.getIncrement();
+            // Use a certain part of the base time, and add increment to that
+            return baseTime / 20 + timeControl.getIncrement();
         }
     }
 

src/main/java/se/dykstrom/ronja/engine/ui/command/AbstractMoveCommand.java

@@ -74,7 +74,7 @@ protected void move() {
             response.write("move " + CanParser.format(move));
 
             // Check game status after move (get new position)
-            if (PositionUtils.isGameOver(game.getPosition())) {
+            if (PositionUtils.isGameOver(game.getPosition(), game)) {
                 notifyUserGameOverOk();
             }
 
@@ -117,8 +117,8 @@ void notifyUserGameOverOk() {
             } else {
                 result = "1-0 {White mates}";
             }
-        } else if (PositionUtils.isDraw(position)) {
-            result = "1/2-1/2 {" + PositionUtils.getDrawType(position) + "}";
+        } else if (PositionUtils.isDraw(position, game)) {
+            result = "1/2-1/2 {" + PositionUtils.getDrawType(position, game) + "}";
         } else {
             result = "?";
         }
@@ -133,8 +133,10 @@ void notifyUserGameOverError(String command) {
         Position position = game.getPosition();
         if (PositionUtils.isCheckMate(position)) {
             response.write("Error (checkmate): " + command);
-        } else if (PositionUtils.isDraw(position)) {
-            response.write("Error (draw): " + command);
+        } else {
+            if (PositionUtils.isDraw(position, game)) {
+                response.write("Error (draw): " + command);
+            }
         }
     }
 }

src/main/java/se/dykstrom/ronja/engine/ui/command/GoCommand.java

@@ -36,7 +36,7 @@ public GoCommand(String args, Response response, Game game) {
 
     @Override
     public void execute() {
-        if (PositionUtils.isGameOver(game.getPosition())) {
+        if (PositionUtils.isGameOver(game.getPosition(), game)) {
             notifyUserGameOverError(NAME);
         } else {
             game.setForceMode(false);

src/main/java/se/dykstrom/ronja/engine/ui/command/HintCommand.java

@@ -43,7 +43,7 @@ public HintCommand(String args, Response response, Game game) {
     public void execute() {
         OpeningBook book = game.getBook();
         Position position = game.getPosition();
-        if (!PositionUtils.isGameOver(position)) {
+        if (!PositionUtils.isGameOver(position, game)) {
             int move = book.findBestMove(position);
             if (move == 0) {
                 var finder = new AlphaBetaFinder(game);

src/main/java/se/dykstrom/ronja/engine/ui/command/PlayOtherCommand.java

@@ -37,7 +37,7 @@ public PlayOtherCommand(String args, Response response, Game game) {
 
     @Override
     public void execute() {
-        if (PositionUtils.isGameOver(game.getPosition())) {
+        if (PositionUtils.isGameOver(game.getPosition(), game)) {
             notifyUserGameOverError(NAME);
         } else {
             game.setForceMode(false);

src/main/java/se/dykstrom/ronja/engine/ui/command/UserMoveCommand.java

@@ -44,7 +44,7 @@ public UserMoveCommand(String move, Response response, Game game) throws Invalid
     public void execute() {
         Position position = game.getPosition();
 
-        if (PositionUtils.isGameOver(position)) {
+        if (PositionUtils.isGameOver(position, game)) {
             notifyUserGameOverError(NAME);
         } else {
             try {
@@ -61,7 +61,7 @@ public void execute() {
                 }
 
                 // If game is over notify user, otherwise make engine's move (in the new position)
-                if (PositionUtils.isGameOver(game.getPosition())) {
+                if (PositionUtils.isGameOver(game.getPosition(), game)) {
                     notifyUserGameOverOk();
                 } else {
                     move();

src/main/java/se/dykstrom/ronja/engine/utils/PositionUtils.java

@@ -19,6 +19,7 @@
 
 import se.dykstrom.ronja.common.model.Board;
 import se.dykstrom.ronja.common.model.Color;
+import se.dykstrom.ronja.common.model.Game;
 import se.dykstrom.ronja.common.model.Position;
 import se.dykstrom.ronja.engine.core.FullMoveGenerator;
 
@@ -44,8 +45,8 @@ public static boolean isLegal(Position position) {
     /**
      * Returns {@code true} if the game is over, that is, if the given position is draw or checkmate.
      */
-    public static boolean isGameOver(Position position) {
-        return isCheckMate(position) || isDraw(position);
+    public static boolean isGameOver(Position position, Game game) {
+        return isCheckMate(position) || isDraw(position, game);
     }
 
     /**
@@ -74,15 +75,15 @@ public static boolean isCheckMate(Position position) {
     /**
      * Returns {@code true} if the given position is a draw.
      */
-    public static boolean isDraw(Position position) {
-        return getDrawType(position) != null;
+    public static boolean isDraw(Position position, Game game) {
+        return getDrawType(position, game) != null;
     }
 
     /**
      * Returns a string describing the type of draw in the given position, or {@code null}
      * if the given position is not a draw at all.
      */
-    public static String getDrawType(Position position) {
+    public static String getDrawType(Position position, Game game) {
         if (isDrawByFiftyMoveRule(position)) {
             return "Fifty move rule";
         }
@@ -91,7 +92,7 @@ public static String getDrawType(Position position) {
             return "Insufficient mating material";
         }
 
-        if (isDrawByThreefoldRepetition(position)) {
+        if (isDrawByThreefoldRepetition(position, game)) {
             return "Threefold repetition";
         }
 
@@ -126,9 +127,22 @@ private static boolean isDrawByStalemate(Position position) {
 
     /**
      * Returns {@code true} if the given position is a draw by threefold repetition of position.
+     *
+     * @param position The position to check.
+     * @param game A reference to the current game that contains all positions that have occurred so far.
+     * @return True if a draw was found.
      */
-    private static boolean isDrawByThreefoldRepetition(Position position) {
-        return false;
+    private static boolean isDrawByThreefoldRepetition(Position position, Game game) {
+        int count = 1;
+        int index = game.positionIndex - 2;
+        while (index >= 0 && count < 3) {
+            if (position.equalTo(game.positions[index])) {
+                count++;
+            }
+            index--;
+        }
+
+        return count >= 3;
     }
 
     /**

src/test/java/se/dykstrom/ronja/engine/time/TimeUtilsTest.java

@@ -22,6 +22,7 @@
 import java.text.ParseException;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
 import static se.dykstrom.ronja.engine.time.TimeControlType.*;
 import static se.dykstrom.ronja.engine.time.TimeUtils.*;
 
@@ -40,6 +41,7 @@ public class TimeUtilsTest {
     private static final TimeControl TC_40_2_30_0 = new TimeControl(40, 150 * 1000, 0, CLASSIC);
     private static final TimeControl TC_40_25_0 = new TimeControl(40, 25 * 60 * 1000, 0, CLASSIC);
 
+    private static final TimeControl TC_0_0_3 = new TimeControl(0, 0, 3 * 1000, SECONDS_PER_MOVE);
     private static final TimeControl TC_0_0_30 = new TimeControl(0, 0, 30 * 1000, SECONDS_PER_MOVE);
 
     @Test
@@ -87,18 +89,20 @@ public void testParseStText_TwoArguments() throws Exception {
 
     @Test
     public void testCalculateTimeForNextMoveClassic() {
-        assertEquals(7500, calculateTimeForNextMove(TC_40_5_0, TimeData.from(TC_40_5_0)));
-        assertEquals(9000, calculateTimeForNextMove(TC_10_1_30_0, TimeData.from(TC_10_1_30_0)));
+        assertTrue(calculateTimeForNextMove(TC_40_5_0, TimeData.from(TC_40_5_0)) > 7500);
+        assertTrue(calculateTimeForNextMove(TC_10_1_30_0, TimeData.from(TC_10_1_30_0)) > 9000);
     }
 
     @Test
     public void testCalculateTimeForNextMoveIncremental() {
-        assertEquals(90000, calculateTimeForNextMove(TC_0_30_5, TimeData.from(TC_0_30_5)));
-        assertEquals(50, calculateTimeForNextMove(TC_0_30_5, TimeData.from(TC_0_30_5).withRemainingTime(1000)));
+        TimeData timeData = TimeData.from(TC_0_30_5);
+        assertEquals(95000, calculateTimeForNextMove(TC_0_30_5, timeData.withRemainingTime(30 * 60 * 1000 + 5 * 1000)));
+        assertEquals(5050, calculateTimeForNextMove(TC_0_30_5, timeData.withRemainingTime(1000 + 5 * 1000)));
     }
 
     @Test
     public void testCalculateTimeForNextMoveSecondsPerMove() {
-        assertEquals(29950, calculateTimeForNextMove(TC_0_0_30, TimeData.from(TC_0_0_30)));
+        assertEquals(2700, calculateTimeForNextMove(TC_0_0_3, TimeData.from(TC_0_0_3)));
+        assertEquals(29500, calculateTimeForNextMove(TC_0_0_30, TimeData.from(TC_0_0_30)));
     }
 }

src/test/java/se/dykstrom/ronja/engine/utils/PositionUtilsTest.java

@@ -34,25 +34,29 @@
  */
 public class PositionUtilsTest extends AbstractTestCase {
 
+    private final Game game = new Game(OpeningBook.DEFAULT);
+
     @Test
     public void testIsGameOver() throws Exception {
-        assertFalse(PositionUtils.isGameOver(FenParser.parse(FEN_START)));
-        assertFalse(PositionUtils.isGameOver(FenParser.parse(FEN_END_GAME_0)));
-        assertFalse(PositionUtils.isGameOver(FenParser.parse(FEN_DRAW_1_1)));
-        assertFalse(PositionUtils.isGameOver(FenParser.parse(FEN_CHECKMATE_1_2)));
-        assertTrue(PositionUtils.isGameOver(FenParser.parse(FEN_DRAW_1_2)));
-        assertTrue(PositionUtils.isGameOver(FenParser.parse(FEN_CHECKMATE_1_3)));
-        assertTrue(PositionUtils.isGameOver(FenParser.parse(FEN_SCHOLARS_MATE)));
-        assertTrue(PositionUtils.isGameOver(FenParser.parse(FEN_ONE_BISHOP)));
+        assertFalse(PositionUtils.isGameOver(FenParser.parse(FEN_START), game));
+        assertFalse(PositionUtils.isGameOver(FenParser.parse(FEN_END_GAME_0), game));
+        assertFalse(PositionUtils.isGameOver(FenParser.parse(FEN_DRAW_1_1), game));
+        assertFalse(PositionUtils.isGameOver(FenParser.parse(FEN_CHECKMATE_1_2), game));
+
+        assertTrue(PositionUtils.isGameOver(FenParser.parse(FEN_DRAW_1_2), game));
+        assertTrue(PositionUtils.isGameOver(FenParser.parse(FEN_CHECKMATE_1_3), game));
+        assertTrue(PositionUtils.isGameOver(FenParser.parse(FEN_SCHOLARS_MATE), game));
+        assertTrue(PositionUtils.isGameOver(FenParser.parse(FEN_ONE_BISHOP), game));
     }
 
     @Test
     public void testIsDraw() throws Exception {
-        assertFalse(PositionUtils.isDraw(FenParser.parse(FEN_START)));
-        assertFalse(PositionUtils.isDraw(FenParser.parse(FEN_CHECKMATE_1_3)));
-        assertFalse(PositionUtils.isDraw(FenParser.parse(FEN_DRAW_1_1)));
-        assertTrue(PositionUtils.isDraw(FenParser.parse(FEN_DRAW_1_2)));
-        assertTrue(PositionUtils.isDraw(FenParser.parse(FEN_ONE_BISHOP)));
+        assertFalse(PositionUtils.isDraw(FenParser.parse(FEN_START), game));
+        assertFalse(PositionUtils.isDraw(FenParser.parse(FEN_CHECKMATE_1_3), game));
+        assertFalse(PositionUtils.isDraw(FenParser.parse(FEN_DRAW_1_1), game));
+
+        assertTrue(PositionUtils.isDraw(FenParser.parse(FEN_DRAW_1_2), game));
+        assertTrue(PositionUtils.isDraw(FenParser.parse(FEN_ONE_BISHOP), game));
     }
 
     @Test
@@ -63,24 +67,24 @@ public void testIsDrawByThreefoldRepetition() {
 
         // Make moves to repeat position
         game.makeMove(MOVE_G1F3);
-        assertNull(PositionUtils.getDrawType(position));
+        assertNull(PositionUtils.getDrawType(game.getPosition(), game));
         game.makeMove(MOVE_G8F6);
-        assertNull(PositionUtils.getDrawType(position));
+        assertNull(PositionUtils.getDrawType(game.getPosition(), game));
         game.makeMove(MOVE_F3G1);
-        assertNull(PositionUtils.getDrawType(position));
+        assertNull(PositionUtils.getDrawType(game.getPosition(), game));
         game.makeMove(MOVE_F6G8);
-        assertNull(PositionUtils.getDrawType(position));
+        assertNull(PositionUtils.getDrawType(game.getPosition(), game));
 
         game.makeMove(MOVE_G1F3);
-        assertNull(PositionUtils.getDrawType(position));
+        assertNull(PositionUtils.getDrawType(game.getPosition(), game));
         game.makeMove(MOVE_G8F6);
-        assertNull(PositionUtils.getDrawType(position));
+        assertNull(PositionUtils.getDrawType(game.getPosition(), game));
         game.makeMove(MOVE_F3G1);
-        assertNull(PositionUtils.getDrawType(position));
+        assertNull(PositionUtils.getDrawType(game.getPosition(), game));
         game.makeMove(MOVE_F6G8);
 
         // Check for draw
-        assertEquals("Threefold repetition", PositionUtils.getDrawType(position));
+        assertEquals("Threefold repetition", PositionUtils.getDrawType(position, game));
     }
 
     @Test