Author: martin fierz
Date: 09:28:05 11/22/00
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On November 22, 2000 at 10:06:24, Robert Hyatt wrote: >On November 22, 2000 at 05:38:32, martin fierz wrote: > >>hi, >> >>i was wondering about this PV-hashtable thing: in my checkers program, i do not >>generate a separate PV. i have two hashtables, a 'shallow' and a 'deep' one, >>positions close to the root of the tree are stored in shallow, the rest in deep. >>in shallow, i take care not to fill the table and not to overwrite entries. i >>took this idea from the crafty source code. in deep i overwrite everything >>without looking twice. question: i have no PV, but i have a guarantee that for >>the first 10 ply i have a hash move - because thats about what fits in shallow. >>for the next 10 ply i won't have a hash move. do you think that this is a >>serious problem? should i be generating a PV and stuffing hash moves back in the >>table (that surely costs some speed...)? typical search depths are 15-19 ply in >>a couple of seconds. do these last 5-9 ply really matter? >> >>cheers >> martin > > >They are often important for debugging, more than anything else. IE the goal >is to play the right move. Nothing says you have to have the right PV, when >playing a game. But if you can't see the PV when testing, you have a harder >problem to understand what is going on and why. > >DB didn't have a separate PV because the hardware didn't support the idea. They >seemed to play just fine. So yes, it can work... thanks for the answer. of course i can get a PV from the hashtable this way, as long as the position is still in the hashtable, which it is for the first 10 ply. but i see what you mean, i could get the whole PV to see which position determines the final evaluation and also to see if the quiescense search is performing properly. i suppose i should implement it :-) cheers martin
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