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Subject: Re: Q: Singular extensions

Author: Robert Hyatt

Date: 20:28:19 01/06/04

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On January 06, 2004 at 10:48:11, Zach Wegner 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.
>
>The way Hsu described it was along the PV, you search all moves like normal, and
>you have two values containing the best and second best scores, and after all
>moves are searched, if the best score is more than the second by a certain
>margin, then research the best move with a deeper depth.

That's not quite accurate.  You search the first move at a PV node normally,
and then you search the remainder of the moves at that node with an offset
(lower) window.  If all fail low, the first move is singular.  You re-search
with depth+1.  If a second fails high, you simply figure out if one is better
than the other by the singular margin by a single re-search.  That is PV-
singular.

He also defined "fail-high" singular, which is a SE that is triggered at a
node where a single move will normally fail high, and you verify that all
the rest fail low on the same offset window.  I can explain further if you
want.

>
>Regards,
>Zach



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