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Subject: Re: Several chess programming questions

Author: Bruce Moreland

Date: 10:39:17 04/07/00

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On April 07, 2000 at 03:42:49, Jan Pernicka wrote:

>  Hi,
> week is over but my head is still full of questions, here they are:
>
> 1) how to quickly identify repetition in the game tree (with help from
>      hash tables, probably) ?

You can do this lots of different ways.  Since you have a hash key already,
that's a pretty good clue that you can use it to make the job easier.

You can use your main hash table to detect repetitions by setting a flag in the
table entry when you "enter" a node, and clearing it when you leave the node.  I
used to do this but it made my hash logic kind of complicated, and I had a few
really cool bugs.

Or you can make a smaller table with a few hundred elements.  It can be a small
table because you know that there won't be more than about 100 things in it,
because of the 50-move rule, so you can make it a few hundred elements in order
to avoid collisions.  This method is simpler and doesn't cause main hash table
bugs.

> 2) when reading some info about Zarkov there were mentioned, without
>    explanation, techniques as "reduced depth search" and "threat heuristics"
>     - so how and when can they be used?
>     Note: They were not mentioned in any context so to include that text
>            here wouldn't be useful...
> 3) does "razoring" mean pruning in general (or even alfa-beta method)?

It's a name given to one of the ways of pruning crap out near the leaves, but
honestly I don't know which one.  There are several ways of doing it, and some
of the ways seem to have names and some don't.

bruce

>
>  Thank you in advance
>
>       Jan



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