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Subject: Re: Q: Singular extensions

Author: Jeremiah Penery

Date: 16:51:07 01/06/04

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On January 06, 2004 at 18:45:34, Tord Romstad wrote:

>On January 06, 2004 at 16:24:07, Robert Hyatt wrote:
>
>>Yes, but Ferret is not using Hsu's Singular Extension algorithm.  not even
>>close.  Bruce is using a "SE approximation" that works very well, but it is
>>not to be confused with what Hsu defined as singular extensions.
>>
>>I did the full DB implementation in Cray Blitz, and using non-recursive
>>null-move R=1, it seemed to work pretty well.  I have tried it more than
>>once in Crafty, and it simply did not work reasonably whatever I tried.  I've
>>not decided that it is hopeless, but I have not played with it further in at
>>least a couple of years now...
>
>Have you experimented with Bruce's approximation as well?  What were the
>results?
>I am tempted to try something similar to singular extensions myself some day,
>but
>I'm afraid I would have to modify the idea a bit to make it work with my MTD(f)
>search.
>
>>I came to the same conclusion that somehow, null-move with bigger R values simply
>>doesn't work very well.  You extend, but null-move reduces the depth and things get
>>lost in the middle.
>
>That's interesting -- I have precisely the opposite experience.  Small R values
>have never
>worked for me, except in the endgame.

He's talking about mixing larger R-value null move with singular extensions,
which is more difficult to make work.  Crafty normally uses R=2-3 depending on
depth.



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