Half the variations which are calculated in a tournament game turn out to be completely superfluous. Unfortunately, no one knows in advance which half.
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[Event "rated untimed match"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "Unknown"]
[Black "Unknown240"]
[Result "0-1"]
[Annotator "David Hayes"]
[BlackElo "0"]
[FEN "8/6p1/4p1k1/6Pp/3Pp2P/4P1K1/8/8 b - - 0 1"]
[SetUp "1"]
[TimeControl "0"]
[WhiteElo "0"]
1... Kf5 2. Kh3 e5 3. d5 Kg6 4. Kg3 Kf7 5. Kf2 Ke7 6. Ke2 Kd6 7. Kd2 Kxd5 8. Kc3 Ke6 9. Kc4 Kf5 10. Kd5 Kg4 ( { Black can try: } 10... g6 11. Kd6 Kg4 12. Kxe5 Kxh4 13. Kf6 Kg4 14. Kxg6 h4 15. Kf6 h3 16. g6 h2 17. g7 h1=Q 18. g8=Q+ Kf3 19. Qf7 Kxe3 20. Qb3+ Kf2 21. Qc2+ Kf3 22. Qc3+ Kg4 23. Qc8+ Kg3 { Draw. Black cannot escape the checks. } ) 11. Kxe5 Kxh4 12. Kf5 Kg3 13. Kg6 h4 14. Kxg7 h3 15. Kf6 h2 16. g6 h1=Q 17. g7 Qh7 18. Kf7 Kf3 19. Kf8 Qf5+ 20. Ke8 Qg6+ 21. Kf8 Qf6+ 22. Kg8 Kxe3 { Black wins with a large material
advantage. } 0-1