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Subject: Re: table-based SEE or "evaluation in rebel (hanging pieces)"

Author: Ed Schröder

Date: 14:48:29 11/27/03

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On November 27, 2003 at 15:34:24, Tord Romstad wrote:

>On November 27, 2003 at 12:39:06, Ed Schröder wrote:
>
>>On November 27, 2003 at 07:54:50, martin fierz wrote:
>>
>>>am i missing something here, or is this just another inaccuracy that such a
>>>table-based SEE has (like not resolving xray attacks)? is it simply unimportant
>>>to resolve such details?

>>It depends how you are planning to use the information, it is great for
>>move-ordering, q-search, static selective search, pruning, extensions,
>>reductions, eval.

>I've always wondered how you manage with only one bit for knights and bishop
>in your eval, for instance when using the attack table for static mate
>detection.  How is this done?

Static mate detection, why should one do this when you have q-search?

I have done so at the very beginning, on the Z80 I had a working static
checkmate algorithm which was called everytime a move gave a check, those were
the days I never heard of q-search and I evaluated hanging pieces on a static
base.


>My attack tables are similar to yours, but
>the way my eval currently works I need 9 bits instead of 8 because of the
>important distinction between knights and bishops.

My system was developed on the Z80 from the early 80's, 9-bits was a non option
at that time :)

I agree that with an 8-bit system to extract the information is more complicated
than with a 9-bit system nevertheless it is doable. I am pretty sure the error
margin in practice is somewhere between 0.1% and 0.01% which is more than
satisfying.



>Another question:  How did you do hanging piece detection and similar
>stuff at the time when the memory for lookup tables was limited (like
>on the ChessMachine version of Rebel and on versions for various Mephisto
>standalone units)?

I used code, later I precalculated the results. Actually the speed gain was
disappointing, less than 1%, probably due to the extra use of the PC's data
cache.



>Thank you very much for making your ideas public!  Your Rebel pages
>is the most valuable chess programming resource out there, IMHO.  They
>contain loads of interesting and useful information.

Thank you, that was the intend.

My best,

Ed



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