Fix en passant in do_move() - Githubissues

basil00 / Fathom

Syzygy TB probe tool.

MIT License

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Fix en passant in do_move() #11

Closed niklasf closed 8 years ago

niklasf commented 8 years ago

Check out 8/8/8/8/6pP/8/8/k6K b - h3 0 1. Last move was h4, allowing en passant on the next move.

h5 should not be a legal move, because that pawn should have been captured.

[Event ""]
[Site ""]
[Date "??"]
[Round "-"]
[White "Syzygy"]
[Black "Syzygy"]
[Result "1/2-1/2"]
[FEN "8/8/8/8/6pP/8/8/k6K b - h3 0 1"]
[WDL "Draw"]
[DTZ "0"]
[WinningMoves ""]
[DrawingMoves "gxh3"]
[LosingMoves "Kb1, Ka2, Kb2, g3"]

1... gxh3 2. h5 Kb1 3. h6 Ka1 4. h7 Kb1 5. h8=Q Kc1 6. Qxh3 Kb2 7. Kg1 Kb1 8. Kf1 Kc1 9. Ke1 Kc2 10. Ke2 Kb1 11. Kd1 Ka1 12. Kc1 Ka2 13. Kc2 Ka1 14. Qa3# 1-0

The fix is similar to https://github.com/basil00/Fathom/commit/45ae9beb1e813e3306ddcd871f7df3493aa35849#diff-98bbf44ad0a296906914322f9b11cd63L1350.

basil00 commented 8 years ago

I had forgotten there was also a do_move in fathom.c. Thanks for spotting this.