Author: Uri Blass
Date: 19:59:57 01/15/03
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On January 15, 2003 at 18:50:29, David Rasmussen wrote: >On January 15, 2003 at 18:38:38, Nathan Thom wrote: > >>I just realised that my program LittleThought (in progress, hoping noone has yet >>used this name?) only stores the best move in the hash table, so when a hash hit >>occurs it cannot display the entire PV for that depth like everyone else's seems >>to. >> >>Do you all store the entire PV in the hash entry? or some other trick im >>missing? > >No one stores the pv, it takes to much space. > >In general, you can't always get the entire PV if you use hashing, and you do if >you want a serious program. Only if you use the hash tables for pruning. 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). 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). 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). Uri
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