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Subject: Re: Q: Singular extensions

Author: Robert Hyatt

Date: 19:47:37 01/06/04

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On January 05, 2004 at 19:24:31, Bas Hamstra wrote:

>On January 05, 2004 at 08:48:23, José Carlos wrote:
>
>>  Hi, I'd like to try singular extensions in my program. I've been trying to
>>think about it and all my tries so far result in worse performance. After some
>>web search I haven't been able to find anything but the general idea described.
>>  Is there any good description somewhere? Some pseudo-code? I guess there must
>>be something interesting in the archives but I can't download all of them.
>>  Thanks in advance,
>>
>>  José C.
>
>Here is what I tried (idea from Bruce I believe):
>
>Before you search all moves (after nullmove) you search all moves (unsorted)
>with D-R and check if there is one and only one move with a score above alpha
>*and* above Alpha-Margin. If so, in the normal search to depth D extend that
>move. I did not do this in nullwindow searches, or else performance crashed. No
>great results. In particular I didn't see much spectacular long pv's show up.
>

One addition I think Bruce and I both tested.  What you are looking for is a
quick fail-high on one move, while all others fail low on a much lower window
to prove "singularity".  However, if the first N moves (4 is what I think I
last tried) all failed low, I quit, since this might be an "all node" where
there can be no reasonable definition of "singularity".

If you want more details, I can provide at least what I tried myself.

BTW I don't think either of us searched "unsorted".  We tried our normal
move ordering so that the "4 move bailout" could be reliably used.



>I am interested in refinements or other approaches. And are there good
>testpositions to check the effect of SE?
>
>
>Best regards,
>Bas.



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