Computer Chess Club Archives




Subject: Re: Nullmove: when to avoid it?

Author: J. Wesley Cleveland

Date: 10:01:52 03/02/01

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On March 01, 2001 at 06:44:58, Severi Salminen wrote:

>>There is another point, unrelated to hashing,
>>which I forgot to mention in my original question.
>>Since we are hoping for fail high, it seems to
>>me obvious that nullmoves are also useless if
>>beta = inf, where inf is the maximum value,
>>used in the largest possible window. Perhaps this
>>is so obvious that nobody mentions it?
>Yep, that's true. As Bob said it is very rare to have beta=INF. Actually
>Beta=INF can occur only in the very beginning of the search until we get our
>first real score (score<=INF-Ply). Remember also that you don't have to know
>anything else about the nullmove but whether its score is >=beta. So you can
>search with (-beta,-beta+1)
An idea I had, is that since about half the time we expect a move to fail low,
it doesn't make much sense to give the opponent an extra move and expect it to
fail high.

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