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Subject: Re: Returning PV from hash table

Author: Nathan Thom

Date: 21:09:04 01/15/03

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On January 15, 2003 at 22:59:57, Uri Blass wrote:

>If you use hash tables but not for pruning you can always get the entire pv.
>Movei still does not use hash tables for pruning but only for order of moves
>because the last time that I tried using hash tables for pruning test positions
>showed that the result is not better.
>One possible reason is the fact that I do not store partial extensions in the
>hash tables(I thought that it still may be better to avoid search and use the
>result at depth k to prune expensive search at depth k+partial but tests showed
>that it cause more problems).

I dont understand how using hash tables for pruning would not speed the search?

>Another possible reason is my different pruning methods that mean that I do not
>always get the same result when I search the same depth from the same position
>even when the partial extensions are the same(it is the same for everybody who
>use repetition detection but I have more reasons).

I also dont understand why you dont get the same result when searching the same
position to the same depth each time. What does repetition detection do to
affect this?

>When I decided to prune only when the depth is bigger and not equal to the
>reported depth I also got slightly worse results(usually I was slightly faster
>but there were still few cases when I got the solution one ply later).
>Maybe the fact that I got slightly worse result was bad luck but I prefered
>simply not to use hash tables for pruning because I have no time to check if
>this is a small improvement or not a small improvement.
>I am not going to change it for the cct5 because it is not something that I can
>change in the last minute and it is more important for me to add better
>evaluation of king safety and maybe better eval of pawn structure(not sure if I
>will do it).

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