Author: milix
Date: 04:39:37 05/27/04
Hello! Chess enging bugs (CEBUGS) are very different than normal bugs (BUGS). They are very good in hiding from debuggers. They are also very good in covering one another so the engine seems to behave normaly, except if it plays a very important match. Sometimes CEBUGS are very productive and when they are eliminated the engine's strength drops about 50-150 points. Of course they have to be eliminated otherwise the engine cannot deliver a mate in KQvsK or it always thinks that passed pawns are Gods. CEBUGS are also layered and they are very cooperative. In the first layer we have the evaluation bugs (usualy + instead of -). In the next layer we can find search bugs (improper alpha - beta windows, or wrong score sign or null-move bugs). In the final layer we meet the most powerful bugs ever, the transposition table bugs. These bugs have a stealth ability, they are protecting the bugs in the first two layers while their actions mimic the behaviour of an evaluation term or a search property (like failing low). I am sure that other bugs exists in my engine but I haven't had the honor to meet them yet. PS: In the Null-Move search you might have forgotten to clear the ep-square as well as to restore it. This bug is very easy to detect and fix. But if you have forgotten to update the hash signature (if you encode ep square in the hash signature) then you are very lucky. You have met a Predator-like bug.
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Last modified: Thu, 15 Apr 21 08:11:13 -0700
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