Author: Steven Edwards
Date: 22:48:59 04/29/05
Embarrassing moments in computer chess Every author enjoys the experience of seeing his program shine in an OTB computer chess event. A clever win, a hard fought draw against a stronger opponent, and the occasional brilliant move are things that are remembered for years thereafter. But what about the incidents that an author would have rather had not happen? Not so much fun, yet they are often more instructive. I will start out with a story of an unfortunate event that occurred in the OTB play of my old program Spector. Back around 1987 when Spector was less than a year old and was still a K&R C program, I was in the habit of entering it into some New England tournaments where it was the only computer program participant. In one of these four round Saturday swiss events, Spector was running on a Macintosh Plus (8 MHz MC68000, later upgraded to a 16 MHz MC68030) and started out the first round looking okay. Well, okay until several moves out of the book. After that the program started to very gradually slow down as the game progressed. (The node frequency was displayed along with the PV trace on the Mac's nine inch porthole CRT.) It lost the first game and the second as well with an even greater slowing down. After it lost the third game, I started to become suspicious. All doubt was gone that there was a yet undiagnosed problem after Spector lost the fourth and last game with its node frequency steadily dropping until it was something like five percent of what it was in pre-event testing. What had happened? I had earlier come up with a "clever" way of recycling move vector storage. And it worked rather well in the many, many pre-event test suite runs. (This was pre-EPD and all the suites were fairly short.) Alas, I had completely neglected to run a single whole game test after my clever modification, and that modification in practice worked reliably only once per program initialization. After a game was started, the program never released much of its allocated storage and so it had to work more and more to allocate less and less. The four straight losses were an amusement to the human entrants and a lesson to me to do full game testing prior to an event. What other embarrassing moments can be shared?
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