COKO III - Genie, United States Computer Chess Championship, 1971. White to move.
Not, you might suppose, the trickiest position a computer has ever faced. After all, white not only has a mate in one available, but a choice of mates in one - not to mention various mates in two (including the artistic 38.Qa1+! Kxa1 39.Bc4#), mates in three, four, and more. Except, for COKO III, this choice was the problem itself: it had not been programmed how to choose between alternate mates.
So it didn't. Instead it played something else entirely, the game continuing 38. Kc1 f5 39. Kc2 f4 40. Kc1 g4 41. Kc2 f3 42. Kc1 fxg2 43. Kc2 gxh1=Q, and thus reaching this position:
The damage done by white's time-wasting is not yet final; COKO still has a choice of two one-move mates. Ah, two: that terrible number, still one too many. Christian Kongsteds in How to Use Computers to Improve Your Chess: "the program could still not decide to mate the black king and so it chose a line that does not lead to mate at all. COKO III's programmers were quite depressed at this point."
So in our second diagram COKO chose 44.Kc1?? and the game concluded 45... Qxf1+ 46. Kd2 Qxf2+ 47. Kc1 Qg1+ 48. Kc2 Qxh2+ 49. Kc1 Qh1+ 50. Kc2 Qb1+ 51. Kd2 g3 52. Qc4+ Qb3 53. Qxb3+ Kxb3 54. e4 Kxb4 55. e5 g2 - at which point the programmers resigned for COKO, rather than wait with the faint hope that Genie's programming suffered from a similar bug.
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