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Subject: Re: King danger extensions

Author: Peter McKenzie

Date: 20:06:12 02/16/99

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On February 16, 1999 at 22:34:32, Robert Hyatt wrote:

>On February 16, 1999 at 16:26:53, James Robertson wrote:
>
>>My program keeps falling prey to king attacks. Although it does very well
>>tactically when it's king is not threatened, it frequently plays combinations
>>that win material (it thinks), only to find, say, a back-rank mate that went
>>unnoticed. I am using a one-reply-to-check extension, the mate extension after
>>null move, and extending half a ply whenever there is a check in the tree. No

I haven't tried the mate extension after null move yet, do you think it is very
effective?

>>check detection is done in the q-search. Are there any other standard check
>>extensions I am not doing?

I've heard that some programs extend on captures by (or adjacent to maybe) the
King, but I've never tried this.

>>
>>James
>
>Half a ply for check is very conservative.  I use 1 ply for all checks, 3/4
>ply for one-legal-reply-to-check...

Yes, I extend a full ply for check - I think this is pretty standard.
I don't do partial ply, so I limit the number of one-legal-reply-to-check
extensions to something like 3 in any given branch of the search tree.

>
>but speed is the main thing you need.  Or else resorting to selective approaches

q-srch is of course a selective search, I think it is a common idea to try
checks in the q-srch.  Either only in the first N ply of q-srch or only 'good
looking' checks.

The other thing to try is playing all responses to check in the q-srch, even if
they aren't captures.

These changes to your q-srch will of course cost you nodes, it is debatable
whether they are worthwhile.

>to get the depth you need.  Or else tuning your evaluation to protect your king
>better.  The chess servers will _really_ help you do this, of course...

Sure does!

Peter



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