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Subject: Re: Deep Search Extension

Author: Heiko Mikala

Date: 16:24:56 01/21/98

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On January 21, 1998 at 18:59:08, Stuart Cracraft wrote:

>On January 21, 1998 at 18:52:44, Heiko Mikala wrote:
>
>>I tried Bruce's mate threat extension (everyone did, I guess...), and it
>>works fine.
>
>Could you elaborate on how you tried it, how you tested it, and why you
>think it worked?

First of all I'm using a "normal" null-move with zero-width window and a
depth reduction of 2 plys.
Unlike Crafty, I do only extend, if the side to move would be directly
mated in the next move. I didn't try the Crafty approach of extending
for all mates yet.
The test was mainly done on the win at chess position, that was men-
tioned here (I guess it was number 141) and the equivalent but easier
position number 17 of the BT2630 test. After that I ran the whole BT-
test and the Bratko-Kopec test suite to see if there are any negative
effects of this extension.  As far as I remember there were no negative
effects, but the two positions in question were solved 1 ply earlier and
much faster in time. I'm sorry, but I don't have the exact test results
any more, because at about the same time I added the one-reply-
extension and only recorded the results of these two extensions to-
gether.

By the way, at the moment I'm experimenting with removing some
of my extensions, because I think I'm doing to many (or the wrong
ones...) On the other hand, I'm "in love" with extensions, and would
like to add more of them... ;-)

Heiko.



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