Author: Andrew Williams
Date: 01:38:08 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
In my (single-threaded) program, there are:
(1) The hash-table - search the previous move for 10 seconds one time and
for 30 seconds the next time and you will have different information
supporting the search.
(2) The order of the pieces in my piecelist[] data structure. For a long
while I was confused by the fact that if I ran postmodernist on a test
position from the command line I got a different search from what I got
running it under Xboard. The problem was that reading a position from fen
put the pieces in a different order from reading the same position from
xboard's "Edit Position" command. (I should say that this depends a bit
on your approach to move generation). I solved this by taking what I
got from "Edit Position", converting it to FEN and reading it back in.
(3) Bugs! I would look at uninitialized variables first.
Best regards
Andrew
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