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Subject: Re: Question for the MTD(f) experts

Author: Vasik Rajlich

Date: 02:48:07 04/14/04

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On April 14, 2004 at 05:38:17, Tord Romstad wrote:

>On April 14, 2004 at 05:32:37, Richard Pijl wrote:
>
>>>So my next question is, how do you normally populate a hash table with PV nodes,
>>>since we only get edge values during the search?  Do I need to follow the pv
>>>from hash to hash with a makemove for each succeeding pv node?
>>>{ICK}
>>
>>In addition to storing the move that gets a fail high, you could also store the
>>bestmove (i.e. score with highest value below alpha) in the hashtable. This only
>>makes some sense with fail soft. With fail hard (as TSCP is) you will (almost)
>>always get alpha as best value so the chosen move will be random.
>>
>>That way you will be able to construct an estimation of the pv, which will
>>improve with each iteration.
>
>Does this really work for you?  I once tried it, and the results were ugly.  In
>my experience, it is never a good idea to store a best move except when failing
>high.
>
>Tord

This is a tiny but clear improvement for Rybka, and a huge improvement in PV
quality.

How good is your fail-soft?

I don't just mean returning the fail-soft value.

I mean, dealing with lazy eval, dealing with scores returned from null move,
dealing with stopping the search in q-search, etc.

Vas



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