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Subject: Practical Alpha-Beta-Conspiracy search

Author: Gian-Carlo Pascutto

Date: 08:38:44 02/13/00


Hi all,

Just for fun, I decided to convert my program to AB-conspiracy search, to see
how I'd work out. The results were not very encouraging...

I have several questions:

first, does anyone here use, used, or tested with AB-conspiracy search ? If so,
what were your results ?

second, the only source of information about ABC-search that I have is the
McAllester/Yuret paper of 1993. It is informative, but I am still wondering
about several things. For example, I am still wondering whether the constant
they use to vary from conspiracy depth to ply depth (page 14) has any effect
on the actual tree shape. Also, what would be a good value for the singular
margin ? A pawn ? Half a pawn ? Even less ?

third, they recommend to use a quiescence search as the static evaluator. But
the ABC-algorithm can do that kind of search automatically due to the way it
works. So why would one use a seperate qsearch function ?

My program seems to have a lot of trouble to archieve even very small conspiracy
depths, resulting in very weak tactical play. This seems to improve as the move
ordering gets better, which is mentioned in the article, but what about those
cases were your ordering can't be possibly right ? (discovering tactical shots)
Its frustrating to see the ABC search look at a position that's mate-in-three
for half an hour and never have it realize what the winning move is just
because it happened to look at the wrong move first. Even with good move
ordering the results are terrible. I can beat the darned thing. Uh! Also, the
gains of using a smaller window seem minimal.

I know there are several strong programs using a variant of conspiracy-number
search, so I am curious as to what advacements they use. Is there any
(preferrably online) source to new developments in this domain?

In short, if anybody has any experience with this kind of search, I'd very
much like to hear about it...

--
GCP



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