DroidFish: Some code re-organization.

DroidFish/src/org/petero/droidfish/DroidFish.java

@@ -107,6 +107,7 @@ public class DroidFish extends Activity implements GUIInterface {
     // FIXME!!! PGN view option: game continuation (for training)
     // FIXME!!! Remove invalid playerActions in PGN import (should be done in verifyChildren)
     // FIXME!!! Implement bookmark mechanism for positions in pgn files
+    // FIXME!!! Display chess notation in local language
 
     // FIXME!!! Computer clock should stop if phone turned off (computer stops thinking if unplugged)
     // FIXME!!! Add support for all time controls defined by the PGN standard
@@ -511,9 +512,8 @@ public class DroidFish extends Activity implements GUIInterface {
 
     @Override
     protected void onDestroy() {
-        if (ctrl != null) {
+        if (ctrl != null)
             ctrl.shutdownEngine();
-        }
         setNotification(false);
         super.onDestroy();
     }
@@ -1552,7 +1552,7 @@ public class DroidFish extends Activity implements GUIInterface {
                         for (int i = 0; i < pvMovesTmp.size(); i++) {
                             ArrayList<Move> pv = pvMovesTmp.get(i);
                             StringBuilder preComment = new StringBuilder();
-                            if (pvStrs.length > i) {
+                            if (i < pvStrs.length) {
                                 String[] tmp = pvStrs[i].split(" ");
                                 for (int j = 0; j < 2; j++) {
                                     if (j < tmp.length) {

DroidFish/src/org/petero/droidfish/GUIInterface.java

@@ -31,7 +31,7 @@ public interface GUIInterface {
     /** Update the displayed board position. */
     public void setPosition(Position pos, String variantInfo, List<Move> variantMoves);
 
-    /** Mark square i as selected. Set to -1 to clear selection. */
+    /** Mark square sq as selected. Set to -1 to clear selection. */
     public void setSelection(int sq);
 
     final static class GameStatus {

DroidFish/src/org/petero/droidfish/engine/CtgBook.java

@@ -271,7 +271,7 @@ public class CtgBook implements IOpeningBook {
             return page;
         }
 
-        final private static int tbl[] = {
+        private final static int tbl[] = {
             0x3100d2bf, 0x3118e3de, 0x34ab1372, 0x2807a847,
             0x1633f566, 0x2143b359, 0x26d56488, 0x3b9e6f59,
             0x37755656, 0x3089ca7b, 0x18e92d85, 0x0cd0e9d8,
@@ -290,7 +290,7 @@ public class CtgBook implements IOpeningBook {
             0x274c7e7c, 0x1e8be65c, 0x2fa0b0bb, 0x1eb6c371
         };
 
-        final private static int getHashValue(byte[] encodedPos) {
+        private final static int getHashValue(byte[] encodedPos) {
             int hash = 0;
             int tmp = 0;
             for (int i = 0; i < encodedPos.length; i++) {

DroidFish/src/org/petero/droidfish/engine/DroidBook.java

@@ -74,6 +74,7 @@ public final class DroidBook {
         rndGen.setSeed(System.currentTimeMillis());
     }
 
+    /** Set opening book options. */
     public final void setOptions(BookOptions options) {
         this.options = options;
         if (CtgBook.canHandle(options))
@@ -136,7 +137,7 @@ public final class DroidBook {
         }
     }
 
-    /** Return a string describing all book moves. */
+    /** Return all book moves, both as a formatted string and as a list of moves. */
     public final Pair<String,ArrayList<Move>> getAllBookMoves(Position pos) {
         StringBuilder ret = new StringBuilder();
         ArrayList<Move> bookMoveList = new ArrayList<Move>();

DroidFish/src/org/petero/droidfish/engine/DroidComputerPlayer.java

@@ -46,11 +46,13 @@ public class DroidComputerPlayer {
     private DroidBook book;
     private boolean newGame = false;
     private String engine = "";
-    private int maxPV = 1;  // >1 if multiPV mode is supported
+    /** >1 if multiPV mode is supported. */
+    private int maxPV = 1;
     private int numCPUs = 1;
 
     private boolean havePonderHit = false;
 
+    /** Constructor. Starts engine process if not already started. */
     public DroidComputerPlayer(String engine) {
         this.engine = engine;
         startEngine();
@@ -58,6 +60,245 @@ public class DroidComputerPlayer {
         book = DroidBook.getInstance();
     }
 
+    /** Set engine and engine strength.
+     * @param engine Name of engine.
+     * @param strength Engine strength, 0 - 1000. */
+    public final synchronized void setEngineStrength(String engine, int strength) {
+        if (!engine.equals(this.engine)) {
+            shutdownEngine();
+            this.engine = engine;
+            startEngine();
+        }
+        if (uciEngine != null)
+            uciEngine.setStrength(strength);
+    }
+
+    /** Set search listener. */
+    public final void setListener(SearchListener listener) {
+        this.listener = listener;
+    }
+
+    /** Return maximum number of PVs supported by engine. */
+    public final synchronized int getMaxPV() {
+        return maxPV;
+    }
+
+    /** Set engine multi-PV mode. */
+    public final synchronized void setNumPV(int numPV) {
+        if ((uciEngine != null) && (maxPV > 1)) {
+            int num = Math.min(maxPV, numPV);
+            uciEngine.setOption("MultiPV", num);
+        }
+    }
+
+    /** Set opening book options. */
+    public final void setBookOptions(BookOptions options) {
+        book.setOptions(options);
+    }
+
+    /** Return all book moves, both as a formatted string and as a list of moves. */
+    public final Pair<String, ArrayList<Move>> getBookHints(Position pos) {
+        return book.getAllBookMoves(pos);
+    }
+
+    /** Get engine reported name, including strength setting. */
+    public synchronized String getEngineName() {
+        if (uciEngine != null)
+            return engineName + uciEngine.addStrengthToName();
+        else
+            return engineName;
+    }
+
+    /** Clear transposition table. */
+    public final void clearTT() {
+        newGame = true;
+    }
+
+    /** Sends "ucinewgame" to engine if clearTT() has previously been called. */
+    public final void maybeNewGame() {
+        if (newGame) {
+            newGame = false;
+            if (uciEngine != null) {
+                uciEngine.writeLineToEngine("ucinewgame");
+                syncReady();
+            }
+        }
+    }
+
+    /** Sends "ponderhit" command to engine. */
+    public final synchronized void ponderHit(Position pos, Move ponderMove) {
+        havePonderHit = true;
+        uciEngine.writeLineToEngine("ponderhit");
+        pvModified = true;
+        notifyGUI(pos, ponderMove);
+    }
+
+    /** Stop the engine process. */
+    public final synchronized void shutdownEngine() {
+        if (uciEngine != null) {
+            uciEngine.shutDown();
+            uciEngine = null;
+        }
+    }
+
+    /**
+     * Do a search and return a command from the computer player.
+     * The command can be a valid move string, in which case the move is played
+     * and the turn goes over to the other player. The command can also be a special
+     * command, such as "draw" and "resign".
+     * @param pos  An earlier position from the game
+     * @param mList List of moves to go from the earlier position to the current position.
+     *              This list makes it possible for the computer to correctly handle draw
+     *              by repetition/50 moves.
+     * @param ponderEnabled True if pondering is enabled in the GUI. Can affect time management.
+     * @param ponderMove Move to ponder, or null for non-ponder search.
+     * @param engineThreads  Number of engine threads to use, if supported by engine.
+     * @return The computer player command, and the next ponder move.
+     */
+    public final Pair<String,Move> doSearch(Position prevPos, ArrayList<Move> mList,
+                                            Position currPos, boolean drawOffer,
+                                            int wTime, int bTime, int inc, int movesToGo,
+                                            boolean ponderEnabled, Move ponderMove,
+                                            int engineThreads) {
+        if (listener != null)
+            listener.notifyBookInfo("", null);
+    
+        if (ponderMove != null)
+            mList.add(ponderMove);
+    
+        havePonderHit = false;
+    
+        // Set up for draw detection
+        long[] posHashList = new long[mList.size()+1];
+        int posHashListSize = 0;
+        Position p = new Position(prevPos);
+        UndoInfo ui = new UndoInfo();
+        for (int i = 0; i < mList.size(); i++) {
+            posHashList[posHashListSize++] = p.zobristHash();
+            p.makeMove(mList.get(i), ui);
+        }
+    
+        if (ponderMove == null) {
+            // If we have a book move, play it.
+            Move bookMove = book.getBookMove(currPos);
+            if (bookMove != null) {
+                if (canClaimDraw(currPos, posHashList, posHashListSize, bookMove) == "") {
+                    return new Pair<String,Move>(TextIO.moveToString(currPos, bookMove, false), null);
+                }
+            }
+    
+            // If only one legal move, play it without searching
+            ArrayList<Move> moves = new MoveGen().pseudoLegalMoves(currPos);
+            moves = MoveGen.removeIllegal(currPos, moves);
+            if (moves.size() == 0) {
+                return new Pair<String,Move>("", null); // User set up a position where computer has no valid moves.
+            }
+            if (moves.size() == 1) {
+                Move bestMove = moves.get(0);
+                if (canClaimDraw(currPos, posHashList, posHashListSize, bestMove) == "") {
+                    return new Pair<String,Move>(TextIO.moveToUCIString(bestMove), null);
+                }
+            }
+        }
+    
+        StringBuilder posStr = new StringBuilder();
+        posStr.append("position fen ");
+        posStr.append(TextIO.toFEN(prevPos));
+        int nMoves = mList.size();
+        if (nMoves > 0) {
+            posStr.append(" moves");
+            for (int i = 0; i < nMoves; i++) {
+                posStr.append(" ");
+                posStr.append(TextIO.moveToUCIString(mList.get(i)));
+            }
+        }
+        maybeNewGame();
+        uciEngine.setOption("Ponder", ponderEnabled);
+        uciEngine.setOption("UCI_AnalyseMode", false);
+        uciEngine.setOption("Threads", engineThreads > 0 ? engineThreads : numCPUs);
+        uciEngine.writeLineToEngine(posStr.toString());
+        if (wTime < 1) wTime = 1;
+        if (bTime < 1) bTime = 1;
+        StringBuilder goStr = new StringBuilder(96);
+        goStr.append(String.format("go wtime %d btime %d", wTime, bTime));
+        if (inc > 0)
+            goStr.append(String.format(" winc %d binc %d", inc, inc));
+        if (movesToGo > 0)
+            goStr.append(String.format(" movestogo %d", movesToGo));
+        if (ponderMove != null)
+            goStr.append(" ponder");
+        uciEngine.writeLineToEngine(goStr.toString());
+    
+        Pair<String,String> pair = monitorEngine(currPos, ponderMove);
+        String bestMove = pair.first;
+        Move nextPonderMove = TextIO.UCIstringToMove(pair.second);
+    
+        // Claim draw if appropriate
+        if (statScore <= 0) {
+            String drawClaim = canClaimDraw(currPos, posHashList, posHashListSize, TextIO.UCIstringToMove(bestMove));
+            if (drawClaim != "")
+                bestMove = drawClaim;
+        }
+        // Accept draw offer if engine is losing
+        if (drawOffer && !statIsMate && (statScore <= -300)) {
+            bestMove = "draw accept";
+        }
+        return new Pair<String,Move>(bestMove, nextPonderMove);
+    }
+
+    public boolean shouldStop = false;
+
+    /** Tell engine to stop searching. */
+    public final synchronized void stopSearch() {
+        shouldStop = true;
+        if (uciEngine != null)
+            uciEngine.writeLineToEngine("stop");
+        havePonderHit = false;
+    }
+
+    /** Start analyzing a position.
+     * @param prevPos Position corresponding to last irreversible move.
+     * @param mList   List of moves from prevPos to currPos.
+     * @param currPos Position to analyze.
+     * @param drawOffer True if other side have offered draw.
+     * @param engineThreads Number of threads to use, or 0 for default value.
+     */
+    public final void analyze(Position prevPos, ArrayList<Move> mList, Position currPos,
+                              boolean drawOffer, int engineThreads) {
+        if (shouldStop)
+            return;
+        if (listener != null) {
+            Pair<String, ArrayList<Move>> bi = getBookHints(currPos);
+            listener.notifyBookInfo(bi.first, bi.second);
+        }
+    
+        // If no legal moves, there is nothing to analyze
+        ArrayList<Move> moves = new MoveGen().pseudoLegalMoves(currPos);
+        moves = MoveGen.removeIllegal(currPos, moves);
+        if (moves.size() == 0)
+            return;
+    
+        StringBuilder posStr = new StringBuilder();
+        posStr.append("position fen ");
+        posStr.append(TextIO.toFEN(prevPos));
+        int nMoves = mList.size();
+        if (nMoves > 0) {
+            posStr.append(" moves");
+            for (int i = 0; i < nMoves; i++) {
+                posStr.append(" ");
+                posStr.append(TextIO.moveToUCIString(mList.get(i)));
+            }
+        }
+        maybeNewGame();
+        uciEngine.writeLineToEngine(posStr.toString());
+        uciEngine.setOption("UCI_AnalyseMode", true);
+        uciEngine.setOption("Threads", engineThreads > 0 ? engineThreads : numCPUs);
+        String goStr = String.format("go infinite");
+        uciEngine.writeLineToEngine(goStr);
+    
+        monitorEngine(currPos, null);
+    }
+
     private final synchronized void startEngine() {
         boolean useCuckoo = engine.equals("cuckoochess");
         if (uciEngine == null) {
@@ -80,27 +321,6 @@ public class DroidComputerPlayer {
         }
     }
 
-    public final synchronized void setEngineStrength(String engine, int strength) {
-        if (!engine.equals(this.engine)) {
-            shutdownEngine();
-            this.engine = engine;
-            startEngine();
-        }
-        if (uciEngine != null)
-            uciEngine.setStrength(strength);
-    }
-
-    public final synchronized int getMaxPV() {
-        return maxPV;
-    }
-
-    public final synchronized void setNumPV(int numPV) {
-        if ((uciEngine != null) && (maxPV > 1)) {
-            int num = Math.min(maxPV, numPV);
-            uciEngine.setOption("MultiPV", num);
-        }
-    }
-
     private static int getNumCPUs() {
         int nCPUsFromProc = 1;
         try {
@@ -121,15 +341,7 @@ public class DroidComputerPlayer {
         return Math.max(nCPUsFromProc, nCPUsFromOS);
     }
 
-    public final void setListener(SearchListener listener) {
+    private final void readUCIOptions() {
-        this.listener = listener;
-    }
-
-    public final void setBookOptions(BookOptions options) {
-        book.setOptions(options);
-    }
-
-    private void readUCIOptions() {
         int timeout = 1000;
         maxPV = 1;
         while (true) {
@@ -159,13 +371,6 @@ public class DroidComputerPlayer {
         }
     }
 
-    public synchronized String getEngineName() {
-        if (uciEngine != null)
-            return engineName + uciEngine.addStrengthToName();
-        else
-            return engineName;
-    }
-
     /** Convert a string to tokens by splitting at whitespace characters. */
     private final String[] tokenize(String cmdLine) {
         cmdLine = cmdLine.trim();
@@ -181,141 +386,6 @@ public class DroidComputerPlayer {
         }
     }
 
-    /** Clear transposition table. */
-    public final void clearTT() {
-        newGame = true;
-    }
-
-    public final void maybeNewGame() {
-        if (newGame) {
-            newGame = false;
-            if (uciEngine != null) {
-                uciEngine.writeLineToEngine("ucinewgame");
-                syncReady();
-            }
-        }
-    }
-
-    /** Stop the engine process. */
-    public final synchronized void shutdownEngine() {
-        if (uciEngine != null) {
-            uciEngine.shutDown();
-            uciEngine = null;
-        }
-    }
-
-    public final synchronized void ponderHit(Position pos, Move ponderMove) {
-        havePonderHit = true;
-        uciEngine.writeLineToEngine("ponderhit");
-        pvModified = true;
-        notifyGUI(pos, ponderMove);
-    }
-
-    /**
-     * Do a search and return a command from the computer player.
-     * The command can be a valid move string, in which case the move is played
-     * and the turn goes over to the other player. The command can also be a special
-     * command, such as "draw" and "resign".
-     * @param pos  An earlier position from the game
-     * @param mList List of moves to go from the earlier position to the current position.
-     *              This list makes it possible for the computer to correctly handle draw
-     *              by repetition/50 moves.
-     * @param ponderEnabled True if pondering is enabled in the GUI. Can affect time management.
-     * @param ponderMove Move to ponder, or null for non-ponder search.
-     * @param engineThreads  Number of engine threads to use, if supported by engine.
-     * @return The computer player command, and the next ponder move.
-     */
-    public final Pair<String,Move> doSearch(Position prevPos, ArrayList<Move> mList,
-                                            Position currPos, boolean drawOffer,
-                                            int wTime, int bTime, int inc, int movesToGo,
-                                            boolean ponderEnabled, Move ponderMove,
-                                            int engineThreads) {
-        if (listener != null)
-            listener.notifyBookInfo("", null);
-
-        if (ponderMove != null)
-            mList.add(ponderMove);
-
-        havePonderHit = false;
-
-        // Set up for draw detection
-        long[] posHashList = new long[mList.size()+1];
-        int posHashListSize = 0;
-        Position p = new Position(prevPos);
-        UndoInfo ui = new UndoInfo();
-        for (int i = 0; i < mList.size(); i++) {
-            posHashList[posHashListSize++] = p.zobristHash();
-            p.makeMove(mList.get(i), ui);
-        }
-
-        if (ponderMove == null) {
-            // If we have a book move, play it.
-            Move bookMove = book.getBookMove(currPos);
-            if (bookMove != null) {
-                if (canClaimDraw(currPos, posHashList, posHashListSize, bookMove) == "") {
-                    return new Pair<String,Move>(TextIO.moveToString(currPos, bookMove, false), null);
-                }
-            }
-
-            // If only one legal move, play it without searching
-            ArrayList<Move> moves = new MoveGen().pseudoLegalMoves(currPos);
-            moves = MoveGen.removeIllegal(currPos, moves);
-            if (moves.size() == 0) {
-                return new Pair<String,Move>("", null); // User set up a position where computer has no valid moves.
-            }
-            if (moves.size() == 1) {
-                Move bestMove = moves.get(0);
-                if (canClaimDraw(currPos, posHashList, posHashListSize, bestMove) == "") {
-                    return new Pair<String,Move>(TextIO.moveToUCIString(bestMove), null);
-                }
-            }
-        }
-
-        StringBuilder posStr = new StringBuilder();
-        posStr.append("position fen ");
-        posStr.append(TextIO.toFEN(prevPos));
-        int nMoves = mList.size();
-        if (nMoves > 0) {
-            posStr.append(" moves");
-            for (int i = 0; i < nMoves; i++) {
-                posStr.append(" ");
-                posStr.append(TextIO.moveToUCIString(mList.get(i)));
-            }
-        }
-        maybeNewGame();
-        uciEngine.setOption("Ponder", ponderEnabled);
-        uciEngine.setOption("UCI_AnalyseMode", false);
-        uciEngine.setOption("Threads", engineThreads > 0 ? engineThreads : numCPUs);
-        uciEngine.writeLineToEngine(posStr.toString());
-        if (wTime < 1) wTime = 1;
-        if (bTime < 1) bTime = 1;
-        StringBuilder goStr = new StringBuilder(96);
-        goStr.append(String.format("go wtime %d btime %d", wTime, bTime));
-        if (inc > 0)
-            goStr.append(String.format(" winc %d binc %d", inc, inc));
-        if (movesToGo > 0)
-            goStr.append(String.format(" movestogo %d", movesToGo));
-        if (ponderMove != null)
-            goStr.append(" ponder");
-        uciEngine.writeLineToEngine(goStr.toString());
-
-        Pair<String,String> pair = monitorEngine(currPos, ponderMove);
-        String bestMove = pair.first;
-        Move nextPonderMove = TextIO.UCIstringToMove(pair.second);
-
-        // Claim draw if appropriate
-        if (statScore <= 0) {
-            String drawClaim = canClaimDraw(currPos, posHashList, posHashListSize, TextIO.UCIstringToMove(bestMove));
-            if (drawClaim != "")
-                bestMove = drawClaim;
-        }
-        // Accept draw offer if engine is losing
-        if (drawOffer && !statIsMate && (statScore <= -300)) {
-            bestMove = "draw accept";
-        }
-        return new Pair<String,Move>(bestMove, nextPonderMove);
-    }
-
     /** Wait for engine to respond with bestMove and ponderMove.
      * While waiting, monitor and report search info. */
     private final Pair<String,String> monitorEngine(Position pos, Move ponderMove) {
@@ -355,49 +425,6 @@ public class DroidComputerPlayer {
         }
     }
 
-    public final Pair<String, ArrayList<Move>> getBookHints(Position pos) {
-        Pair<String, ArrayList<Move>> bi = book.getAllBookMoves(pos);
-        return new Pair<String, ArrayList<Move>>(bi.first, bi.second);
-    }
-
-    public boolean shouldStop = false;
-
-    public final void analyze(Position prevPos, ArrayList<Move> mList, Position currPos,
-                              boolean drawOffer, int engineThreads) {
-        if (shouldStop)
-            return;
-        if (listener != null) {
-            Pair<String, ArrayList<Move>> bi = getBookHints(currPos);
-            listener.notifyBookInfo(bi.first, bi.second);
-        }
-
-        // If no legal moves, there is nothing to analyze
-        ArrayList<Move> moves = new MoveGen().pseudoLegalMoves(currPos);
-        moves = MoveGen.removeIllegal(currPos, moves);
-        if (moves.size() == 0)
-            return;
-
-        StringBuilder posStr = new StringBuilder();
-        posStr.append("position fen ");
-        posStr.append(TextIO.toFEN(prevPos));
-        int nMoves = mList.size();
-        if (nMoves > 0) {
-            posStr.append(" moves");
-            for (int i = 0; i < nMoves; i++) {
-                posStr.append(" ");
-                posStr.append(TextIO.moveToUCIString(mList.get(i)));
-            }
-        }
-        maybeNewGame();
-        uciEngine.writeLineToEngine(posStr.toString());
-        uciEngine.setOption("UCI_AnalyseMode", true);
-        uciEngine.setOption("Threads", engineThreads > 0 ? engineThreads : numCPUs);
-        String goStr = String.format("go infinite");
-        uciEngine.writeLineToEngine(goStr);
-
-        monitorEngine(currPos, null);
-    }
-
     /** Check if a draw claim is allowed, possibly after playing "move".
      * @param move The move that may have to be made before claiming draw.
      * @return The draw string that claims the draw, or empty string if draw claim not valid.
@@ -583,11 +610,4 @@ public class DroidComputerPlayer {
             statsModified = false;
         }
     }
-
-    public final synchronized void stopSearch() {
-        shouldStop = true;
-        if (uciEngine != null)
-            uciEngine.writeLineToEngine("stop");
-        havePonderHit = false;
-    }
 }

DroidFish/src/org/petero/droidfish/gamelogic/Game.java

@@ -35,6 +35,7 @@ public class Game {
     private DroidComputerPlayer computerPlayer;
     TimeControl timeController;
     private boolean gamePaused;
+    /** If true, add new moves as mainline moves. */
     private boolean addFirst;
 
     PgnToken.PgnTokenReceiver gameTextListener;
@@ -50,6 +51,7 @@ public class Game {
         newGame();
     }
 
+    /** De-serialize from byte array. */
     final void fromByteArray(byte[] data) {
         tree.fromByteArray(data);
         updateTimeControl(true);
@@ -66,10 +68,12 @@ public class Game {
         }
     }
 
+    /** Set whether new moves are entered as mainline moves or variations. */
     public final void setAddFirst(boolean addFirst) {
         this.addFirst = addFirst;
     }
 
+    /** Sets start position and discards the whole game tree. */
     final void setPos(Position pos) {
         tree.setStartPos(new Position(pos));
         updateTimeControl(false);
@@ -217,6 +221,7 @@ public class Game {
         return nVar > 0;
     }
 
+    /** Get number of variations in current game position. */
     public final int numVariations() {
         if (tree.currentNode == tree.rootNode)
             return 1;
@@ -226,6 +231,7 @@ public class Game {
         return nChildren;
     }
 
+    /** Get current variation in current position. */
     public final int currVariation() {
         if (tree.currentNode == tree.rootNode)
             return 0;
@@ -235,6 +241,7 @@ public class Game {
         return defChild;
     }
 
+    /** Go to a new variation in the game tree. */
     public final void changeVariation(int delta) {
         if (tree.currentNode == tree.rootNode)
             return;
@@ -249,6 +256,7 @@ public class Game {
         updateTimeControl(true);
     }
 
+    /** Move current variation up/down in the game tree. */
     public final void moveVariation(int delta) {
         if (tree.currentNode == tree.rootNode)
             return;
@@ -264,6 +272,7 @@ public class Game {
         updateTimeControl(true);
     }
 
+    /** Delete whole game sub-tree rooted at current position. */
     public final void removeSubTree() {
         if (getLastMove() != null) {
             tree.goBack();
@@ -323,10 +332,14 @@ public class Game {
         }
     }
 
-    public final void goNode(Node node) {
+    /** Go to given node in game tree.
-        tree.goNode(node);
+     * @return True if current node changed, false otherwise. */
+    public final boolean goNode(Node node) {
+        if (!tree.goNode(node))
+            return false;
         pendingDrawOffer = false;
         updateTimeControl(true);
+        return true;
     }
 
     public final void newGame() {

DroidFish/src/org/petero/droidfish/gamelogic/GameTree.java

@@ -657,13 +657,17 @@ public class GameTree {
         }
     }
 
-    /** Go to given node in game tree. */
+    /** Go to given node in game tree.
-    public final void goNode(Node node) {
+     * @return True if current node changed, false otherwise. */
+    public final boolean goNode(Node node) {
+        if (node == currentNode)
+            return false;
         ArrayList<Integer> path = node.getPathFromRoot();
         while (currentNode != rootNode)
             goBack();
         for (Integer c : path)
             goForward(c);
+        return true;
     }
 
     /** List of possible continuation moves. */
@@ -1388,6 +1392,7 @@ public class GameTree {
         }
     }
 
+    /** Set PGN header tags and values. */
     void setHeaders(Map<String,String> headers) {
         for (Entry<String, String> entry : headers.entrySet()) {
             String tag = entry.getKey();
@@ -1417,6 +1422,7 @@ public class GameTree {
         }
     }
 
+    /** Get PGN header tags and values. */
     void getHeaders(Map<String,String> headers) {
         headers.put("Event", event);
         headers.put("Site",  site);

DroidFishTest/src/org/petero/droidfish/gamelogic/GameTreeTest.java

@@ -667,7 +667,8 @@ public class GameTreeTest extends TestCase {
         for (int i = 0; i < 5; i++) gt.goForward(-1);
         assertEquals("e4 e5 Nf3 Nc6 Bb5 a6*", getMoveListAsString(gt));
         Node na6 = gt.currentNode;
-        gt.goNode(gt.rootNode);
+        assertTrue(gt.goNode(gt.rootNode));
+        assertFalse(gt.goNode(gt.rootNode));
         assertEquals("*e4 e5 Nf3 Nc6 Bb5 a6", getMoveListAsString(gt));
         gt.goNode(na6);
         assertEquals("e4 e5 Nf3 Nc6 Bb5 a6*", getMoveListAsString(gt));