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Subject: Re: Zero-width Window Null Move Search

Author: Roberto Waldteufel

Date: 22:32:38 06/18/98

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Hi Don,

Thanks for your detailed description of Cilkchess' MTD(f) implementation. Maybe
I'll try it again at some point, but it sounds quite tricky to get right. I
don't use a lazy evaluation (never have done), but then my normal evaluation is
not very sophisticated. It only takes into account material, bishop pair,
open/semi-open files near kings and attack counts on squares adjacent to kings.
However, I also use a preprocessor which sets square values for all the chessmen
based on those features of the position that are unlikely to change during the
search, such as squares on which pawns would be passed, open/semiopen files for
rooks, squares for rooks behind passed pawns, centrality etc. I have tried other
things, but came to the conclusion that it is best not to attempt preprocessing
features that may change frequently, since then the information is too often
inaccurate at the leaf nodes. I seem to have achieved a fairly good balance
between the things I evaluate in the evaluation function and those I preprocess,
but there are many things I still need to consider, perhaps pawn structure is
the most important omission at present. I would be very interested to know what
were the features that Larry recommended for your preprocessor, and whether any
of these things were later moved to the terminal evaluation to improve accuracy,
albeit at the cost of some speed.

Over the past couple of days I have ported my program from an old 16-bit DOS
compiler to a much superior 32-bit compiler (alas, no alpha 64-bit technology
yet, but Pentium 333MHz is not too slow), and in the process of optimizing my
code for this new platform I have been re-examining the issue of divideing the
evaluation effort between the preprocessor and the evaluation function with a
view to expanding the positional features it considers.

Best Wishes

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