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Subject: Re: fractional extensions/hashing

Author: Tord Romstad

Date: 07:11:00 10/23/03

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On October 22, 2003 at 21:02:04, Zach Wegner wrote:

>when hashing, is it really necessary to hash the exact fractional depth, or is
>it ok to just hash depth/PLY? I am thinking it is better to do the latter
>because it saves space and also if the current depth is (say) 1.3 plies and the
>hash table says 1.2, there wont be a cutoff, while the actual depth searched is
>the same. or is it necessary because you might extend .7 plies on the next ply,
>giving a premature cutoff?

As so often, it's a tradeoff.  Just storing depth/PLY will definitely cause
an increased number of errors and instabilities in the search if you use
any fractional extensions or reductions at all.  Whether the advantage of
saving a few bits in the hash table entries is big enough to compensate for
this is probably impossible to say without experimenting.  I expect that
the results would vary a lot between different programs.

Personally I have always stored the exact fractional depth, and I don't
think I will every try something else.

Tord




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