Nimzo
Joined: 15 Mar 2005
Posts: 64
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 Posted: Mon Jul 21, 2008 5:26 pm Post subject: Undo multithread |
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Undo multithread
Context: Vista Ultimate .NET 3.5, SharpChess v 2.52 Official Release, Level 16, Pondering.
Symptom
Unhandled exception NullReferenceException
Stack: Think, Aspirate, AlphaBeta..., Move.Undo
Board.HashCodeA ^= move.To.Piece.HashCodeA;
Diagnostic
The piece has already been moved in the main UI thread before the Move.Undo in the thread Think.
So move.To.Piece is null. One cannot access to move.To.Piece.HashCodeA.
Tool
In Move.cs, add in debug the conditional breakpoint before the exception:
| Code: | public static void Undo(Move move)
{
#if DEBUG
if (move.To.Piece == null)
Debugger.Break();
#endif
Board.HashCodeA ^= move.To.Piece.HashCodeA; // un_XOR the piece ...
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Suggestion
FrmMain.cs
| Code: | private void StartNormalGame()
{
if (!Game.LoadBackup())
{
frmDifficulty formDifficulty = new frmDifficulty();
formDifficulty.ShowDialog(this);
}
/* 08/07/21 Nimzo: original code
Game.StartNormalGame();
*/
OrientBoard();
RenderBoard();
RenderClocks();
SetFormState();
timer.Start();
// 08/07/21 Nimzo: moved after RenderBoard
// because SetFormState calls CanMove, GenerateLegalMoves, Undo
Game.StartNormalGame();
} // end StartNormalGame
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Even if the problem of the concurrent access to the chess Board during pondering / thinking and the main UI thread is not fully solved, the above suggestion allows to properly restart SharpChess in the context of the scratch stored in the following BackupGame.sharpchess.
| Code: | <Game FEN="8/8/5kN1/7K/8/6PP/8/8 w - - 1 70" TurnNo="138" WhitePlayer="Human" BlackPlayer="Computer" BoardOrientation="White" Version="2.5.2.0" DifficultyLevel="16" ClockMoves="120" ClockSeconds="36000" MaximumSearchDepth="0" Pondering="1" UseRandomOpeningMoves="1" />
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In the Immediate Window, after 69. Kxh5
| Code: | Board.DebugDisplay()
0 1 2 3 4 5 6 7 :PlayerToPlay = White
8:. . . . . . . . :7 x Ng8 Nb8 Bf8 Bc8 Rh8 Ra8 Qd8
7:. . . . . . . . :6
6:. . . . . k N . :5
5:. . . . . . . K :4
4:. . . . . . . . :3
3:. . . . . . P P :2
2:. . . . . . . . :1
1:. . . . . . . . :0 x Nb1 Bf1 Bc1 Rh1 Ra1 Qd1
a b c d e f g h :TurnNo = 138. " "
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The full game in PGN format (the time is between braces):
| Code: | [Event "SharpChess"][Site "?"][Date "2008.07.21"][Round "1"]
[White "Human"][Black "Computer"][Result "1-0"]
[PlyCount "177"][Flip "1"][Ver "3.0.0.0"][Level "16"][Depth "0"]
[Ponder "1"][Book "1"][TimeControl "120/36000"]
1.e4 {11} f6 {0} 2.d4 {19} Nc6 {130} 3.d5 {32} Ne5 {315} 4.f4 {36} Nf7 {431}
5.Nf3 {42} Ngh6 {551} 6.Bd3 {48} e5 {712} 7.O-O {75} exf4 {872} 8.Bxf4 {82} Bc5+ {980}
9.Kh1 {86} Ng4 {1205} 10.Qe2 {90} O-O {1428} 11.h3 {94} Nge5 {1667} 12.Nbd2 {227} Nxd3 {2297}
13.cxd3 {231} a6 {2570} 14.d4 {313} Ba7 {2974} 15.Rac1 {353} d6 {3198}
16.Rc2 {361} Nh8 {3452} 17.Rfc1 {367} Rf7 {3672} 18.Nc4 {409} Ng6 {3919}
19.Bg3 {421} b5 {4064} 20.Na5 {433} Bb6 {4240} 21.Nc6 {449} Qd7 {4390}
22.e5 {495} dxe5 {4543} 23.dxe5 {499} Qxd5 {4779} 24.Rd1 {508} Qxa2 {4889}
25.b4 {598} Qa3 {5023} 26.e6 {608} Rf8 {5294} 27.e7 {618} Re8 {5511} 28.Rd8 {637} Qa1+ {6167}
29.Kh2 {649} Kf7 {6341} 30.Rcd2 {2307} Nxe7 {6555} 31.Rxe8 {2662} Nxc6 {6708}
32.Rxc8 {2670} Rxc8 {6912} 33.Rd7+ {2685} Kg8 {7450} 34.Rd1 {2938} Qxd1 {7892}
35.Qxd1 {2947} Rd8 {8102} 36.Qb3+ {3043} Kh8 {8310} 37.Qc3 {3195} Ne7 {8969}
38.Qa3 {3781} Ra8 {9094} 39.Qd3 {4511} Ng8 {9750} 40.Qd7 {5108} Ra7 {10006}
41.Qc6 {5476} Ne7 {10656} 42.Qe8+ {5572} Ng8 {10850} 43.Nd2 {5709} a5 {11256}
44.bxa5 {5735} Bxa5 {11615} 45.Nb3 {5748} Bb6 {12167} 46.Qxb5 {5981} Ra3 {12657}
47.Bd6 {6153} Ra8 {12986} 48.Qc6 {6766} Rb8 {13125} 49.Nc5 {6989} cxd6 {13360}
50.Nd7 {7152} Ne7 {13998} 51.Qxd6 {7189} Rd8 {14114} 52.Qxe7 {7342} Bc7+ {14664}
53.Kg1 {8406} Rg8 {14853} 54.Nxf6 {9292} Bd8 {15053} 55.Nxg8 {9939} Bxe7 {15232}
56.Nxe7 {9954} h5 {15352} 57.g3 {9964} Kh7 {15483} 58.Kg2 {10019} g6 {15972}
59.Kf3 {10111} Kg7 {16112} 60.Kf4 {10501} Kf6 {16764} 61.Nd5+ {11428} Ke6 {17029}
62.Nc3 {11521} Kd6 {17270} 63.Ne4+ {11775} Ke6 {17916} 64.Kg5 {12209} Kf7 {18234}
65.Nc5 {12772} Kg7 {18361} 66.Ne6+ {12952} Kf7 {18537} 67.Nf4 {13021} Kg7 {18904}
68.Nxg6 {13112} Kf7 {19054} 69.Kxh5 {13718} Kf6 {19168} 70.Kh6 {13839} Ke6 {19550}
71.g4 {13901} Kd5 {19673} 72.Kg7 {14082} Ke4 {19792} 73.h4 {14110} Kf3 {20132}
74.g5 {14136} Kg4 {20484} 75.Kh6 {14188} Kg3 {20700} 76.h5 {14278} Kg4 {20966}
77.Ne7 {14312} Kf4 {21091} 78.g6 {14499} Ke5 {21395} 79.Kg7 {14550} Ke6 {21541}
80.Ng8 {14602} Kd5 {21688} 81.Kf6 {14706} Ke4 {21894} 82.h6 {14872} Kd4 {22095}
83.h7 {14922} Ke4 {22267} 84.h8=Q {14973} Ke3 {22862} 85.Ne7 {15003} Kd3 {22862}
86.g7 {15024} Ke4 {22862} 87.g8=Q {15044} Kd4 {22863} 88.Qh3 {15050} Ke4 {22864}
89.Qgg4# {15063} 1-0
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1... f6 is not the best defense for Black
22. e5 sacrifice of d4 and a2 to win the queen after 34. Rd1 with the threat Qe6+ winning Rc8. |
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