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Subject: Re: significant math

Author: Steffan Westcott

Date: 06:37:11 11/20/02

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On November 20, 2002 at 07:35:46, Sune Fischer wrote:

>You are right that would save time, but I wonder if not the book keeping becomes
>very complex. There seem to be two conflicting issues at work here, doing the
>least amount of effort and get a good move ordering.
>What I don't understand is how you do your move ordering (SEE or MVV/LVA) for
>captures, how do you access the history table without "to" and "from" squares,
>that kind of thing.
>I guess if you do something really simple like: Attack(Whitepawns)&BlackQueens,
>then you can generate that move(s) only and try that, no move ordering needed.
>But there are 5 pieces and each can attack eachother, so that must be 25
>different checks.
>What am I missing here?


I perhaps spend a bit more effort than most on immediate move ordering when the
other heurisitics (transposition table, history, killers etc) are exhausted. I
have a high degree of overlap between (fundamental) position evaluation and SME
(Static Move Evaluation, a generalisation of SEE where the initial move is not
necessarily a capture).

Your example, of testing for instances of the pattern P x Q, is not far off the
mark. The patterns I use for SME are *ahem* somewhat more complex, and mostly
resemble those of interest for standard SEE. The patterns are ordered (from best
to worst) and tested for matches on the board _when_needed_. It essentially
implements a static (predetermined) sequence of move types to try, ordered by
position features that can be discovered quickly without doing a search.
Optimisations are possible to skip patterns if they are known that they will not
currently match anything. For example, if no enemy queen is currently attacked,
all patterns ? x Q can be skipped.

As for indexing the history table, I index it using a move hash value, not the
from/to square indices. It is merely a different hashing scheme than the
traditional [from][to] scheme.


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