Author: martin fierz
Date: 16:14:11 01/28/02
aloha! i am wondering about endgame databases and their verification, maybe someone here can shed some light on the issue: it's regarding the 8-piece checkers endgame database, which was computed by jonathan schaeffer in about '95, and just now by different commercial checkers programmers. one team, world championship checkers, has verified it's database against that of schaeffer, and apparently this verification has found errors in both databases. i wrote a post on a checkers message board saying i believed that an independent verification would not be necessary, to which ed trice of WCC replied below, calling this statement ridiculous. since endgame database construction in checkers is the same as in chess: could somebody comment on the database verification process? how reliable is it? is ed trice right? eugene? : Gentlemen, : : I have been directed to this page by a couple of ACF members who have : inundated me with emails. : : Verifying the 8-piece database was a difficult task. Gil Dodgen and : I found a mistake in the Chinook database which had been present for : 8 years, undetected by the most-tested database on the planet. Dr. : Schaeffer corrected his databases. As we continued to develope our : databases, Dr. Schaeffer's results and ours did not agree again, this : time it was tracked down to 1123 bits that did not copy properly on : *our end.* : : Anyone who states that their database computation does not need : independent verification is rather foolish. The process is very complex, : and hundreds of trillions (I guess a few hundred thousand million in the : English sense) of calculations are performed as your database is being built. : : If your chance of any error creeping in in one in 10,000,000,000 you : will most likely have 100 chances to encounter such an error. Should : one single integrated circuit dip to -0.5 Volts when it should have been : +0.5 Volts (the difference between a binary "0" and a binary "1") even for : a microsecond, your databases will be wrong. : : Dr. Schaeffer will publish a paper on the topic wherein the notion : of "unilateral verification", that is "testing it yourself" once a : database has been computed, is no longer a valid means to assert : correctness. Gil and I will be participating in this paper as contributors. : : So, while you may use whatever rhetoric you wish on this forum, I suggest : you defer to the two teams who have correctly completed the result before : you make ridiculous statements such as I have already seen. : : Any doubts, send an email to Dr. Schaeffer yourself.
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