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Subject: Re: Draw Detection by Move Repetition Procedure -- Comments

Author: Christophe Theron

Date: 11:12:23 08/01/04

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On August 01, 2004 at 13:51:47, vladan wrote:

>Hi Remi,
>"Extender" is Alfa-Beta procedure we use in terminal nodes instead of static
>evaluator. Only a fraction of all generated moves are computed (captures, some
>checks and promotion moves). It is very important to optimize this procedure as
>much as possible.

We call this a "quiescence search" or "QSearch". This term has been used for the
last 50 years I think.

When you publish papers, it is a good idea to use terms that are commonly used
in your field of research.

Or maybe I do not understand what you extender does?

>Hash system used in Axon is simple:
>6 bytes (48 bit):
>24 bit - fractional position key,
>16 bit - best move,
>8 bit - other flags.
>Using this compressed hash system we have tested Axon with 32 million
>positions/best moves memory. All nodes (included ones generated by the extender)
>could be supplied with best moves efficiently.
>Of course, 24-bit is not enough to determine positions exactly (like Zobrist
>64-bit hash); different positions could generate the same 24-bit hash key. But
>those cases (hash failure) are not fatal for searcher - they only could decrease
>quality of move ordering. But if the best move is found, Alfa-Beta, Null-Move
>and Extender procedures could make a great number of cutoffs.
>This is the main reason why our hash could be used for searcher and not for

If I understand correctly, you use your hash table only for move ordering. You
do not use it to produce direct cut-offs. Correct?


>Best regards,
>Vladan      (Axon programmer)

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