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Subject: Re: Nondeterminsitic behavior

Author: Robert Hyatt

Date: 07:05:05 07/18/99

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On July 18, 1999 at 03:01:33, Dave Gomboc wrote:

>In the past, people have discussed how difficult it can be to debug a chess
>program due to non-deterministic behavior.  Clearly, this can arise from a
>multi-threaded search.  If, however, the search is single-threaded (and
>discounting the play from the start of the game until the end of the opening
>book), what factors, if any, might allow a program to still not play identically
>each time?
>
>Dave


Time and hash tables are the other issue.  In a game, while waiting on the
opponent, you search like mad... and this adds/overwrites stuff in the hash
table.  If your program makes a move, and you then try to reproduce it later,
you will find it basically impossible to reproduce the same hash table state
again.  Starting from scratch, this is not a problem when you are searching some
test position.  But in the middle of a game it is nearly imposible.  Even if you
play a game with pondering disabled, you can't exactly reproduce the search,
which means the hash table will still be a variable...



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