Author: Uri Blass
Date: 13:06:00 08/02/01
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On August 02, 2001 at 14:47:20, Dann Corbit wrote: >On August 02, 2001 at 13:00:27, Miguel A. Ballicora wrote: > >>I have an idea for debugging that probably was used before but I want some >>opinions about it: >> >>I am thinking about a system to trace what is going in my engine when I see a >>weird move during a game. The main problem is that it is extremely difficult >>to reproduce the same conditions for search. I have seen once in a while a >>very weird move that I cannot reproduce it if I set the position to search. >>The obvious reason is because the tables, hash and history bring information >>that I lack when I try to reproduce. >>Clearing the tables before each move would be (I think) an easy way out. The >>engine in this state will be easy to debug but I would be dodging the problem. >>In that way I would not see problems caused by the tables. I would be debugging >>probably only part of the engine, dodging the most prone to errors!. >>Saving the tables is out of the question, I would fill my HD in no time. >> >>What I think I can do is to save how many nodes I searched in any particular >>move. When I ran out of time I keep record of the nodes. >>When I try to reproduce the game I set the limit of thinking in "nodes", rather >>than "time". I should be able to reach exactly the same situation in the search >>in each of the moves of the games. Moreover, I should be able to reproduce the >>whole thing with the debug version. Maybe I can store a log with all this >>information and after the game let the program chew it and see if the >>reproduction is exact. >> >>I think that debugging is tedious, boring but extremely important to make the >>engine play the way we want. Particularly for chess programs where >>the bugs are nasty because sometimes the program does not crash, it just plays >>worse "sometimes". >> >>I just came up with this idea this morning, is there anything that I am missing? >>suggestions? Is it obvious and everybody already does this? >> >>Regards, >>Miguel >>PS: I think that this kind of testing could be done also with pondering! >>just limiting the pondering to n = nodes. > >I think to reproduce the exact state of a computer program will be nearly >impossible if there is any way for randomness to be introduced (and surely there >will be such). Why do you think that there will be randomness? > >It's a good idea to try, but don't expect miracles. > >Normally, if I want to reproduce something, I just take the EPD position where >the problem occurred and let the program analyze. If it *never* makes the same >choice it made before at any point in time, you have some very serious problem >anyway (or a large amount of deliberately introduced randomness perhaps). I disagree. It is possible that in the game it learned information from previous search and this is the reason for the fact that it does not produce the same choice again. Uri
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