Author: Dan Homan
Date: 08:38:00 07/01/98
About a week ago I was logged on to ICC to watch my program, EXchess play some games while I worked on a talk I'll be giving in England next week. My program is set up to "tell" me when it is playing a game, so I usually pick up the games sometime in the middle game, after I notice the tell. EXchess had been playing on ICC since early June and had maintained a blitz rating around 2300 on a P133 class machine for 600-700 games. However, on this day I noticed something disturbing.... EXchess was losing a lot, usually to assaults on its King. It's rating had dropped to the low 2100's in a few hours. I had observed some of the games and noticed the way the King was being shredded by its opponents. I thought, "wow, I should fix this", and proceeded to spend time that I didn't have to re-write some of the eval. I added some King safety terms... They didn't work, still lost in the same way. Beefed up the King safety terms and added some more.... This worked some, the rating stopped falling and I watched EXchess defend its King well in some rather sticky situations. By now my eval was slower and my lazy-eval window needed to be larger, slowing down the program further. I tinkered with the eval for a few evenings and managed to really mess things up (Although I didn't know that at the time.). On Saturday I found the problem. My opening book had somehow become corrupted. I was getting a max of 1-2 moves in book. Because I only caught games from the mid-game onward, I had missed this at first. Now, what a smart programmer would do at this stage is to undo all of the unnecessary changes, re-install the original book, and see if things go back to normal. But being the person that I am, I thought, "I've wasted all this time adding these terms to the eval, they are theoretically a good idea anyway, - I'll keep them". Not so easy, the terms were too strong and buggy. I've since toned them down and de-bugged them. (With much added frustration, I might add.) Now play seems to be back to 'normal' and EXchess' rating is on the way back up. I wonder how many other 'problems' I have 'fixed' which turned out not to be the problem at all? Ok, now back to my talk.... :) - Dan
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