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Subject: Re: Extensions and Hashing

Author: Dieter Buerssner

Date: 07:16:45 10/19/00

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On October 19, 2000 at 09:45:23, Robert Hyatt wrote:

>Why would this be a problem?  IE the last time I did this search, I already
>had the threat extension folded in.  The idea is that When I store the result
>of a search, I use a consistent depth, namely the depth I had when I came in to
>the position, which will be the same depth I use when I probe later.  If you
>look at my code, inside a ply I _never_ adjust "depth".  I have a separate
>modifier that is added to it when I recursively call search.
>
>So that 'depth' when I do a probe is exactly the same for this position as
>when I did a store.

I think, it is almost impossible, to do this really correct. What you
describe works for example for check extensions and also on the null threat. But
other extensions may depend on the path, the position is reached. One example
would be recapture. The last move might have been a capture, when you
get the table hit. But when the position was stored, the last move might not
have been a capture move. This probably means for many programs, that some
moves now should be searched deeper, than they were searched, when the position
was stored in the hash table.

Other sources of inconsistencies might be extensions, that depend on the initial
search depth or the ply, and not on the depth left. I think, one just have to
live with these inconsistencies.

-- Dieter



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