Author: Robert Hyatt
Date: 22:03:06 12/30/00
Go up one level in this thread
On December 30, 2000 at 12:37:07, Steve Maughan wrote: >In my program I have the following lines of code after the hash probe: > > if (CurrentHash.Bound = HASH_LOWERBOUND) then > begin > if (CurrentHash.Value >= Beta) then > begin > result := CurrentHash.Value; > exit; > end > //increase the value of alpha if lower bound is greater > else if CurrentHash.Value > Alpha then > begin > alpha := CurrentHash.Value; > PVLength := Ply; > end; > end; > if (CurrentHash.Bound = HASH_UPPERBOUND) then > begin > if (CurrentHash.Value <= Alpha) then > begin > result := CurrentHash.Value; > exit; > end > //see if beta can be lowered > else if CurrentHash.Value < Beta then > begin > Beta := CurrentHash.Value; > end; > end; > >The bit that I'm not sure about and having problems with is the section that >adjusts the value of alpha and beta based upon the hash results. I'm getting >odd PVs and different values returned when I activate this section. I do this in crafty, but it is executed _very_ infrequently due to the PVS search using null-window almost everywhere... > >Is it valid to raise the value of Alpha when the depth is sufficient and the >lowerbound is greater than Alpha? What happens to the PV? I'm just cutting it >off at the moment (i.e. PVLength := Ply). Why bother the PV? You are simply altering the bound. The PV should not be affected by this at all... > >Likewise, is it valid to lower beta based on an upperbound? Again what happens >to the PV? At the moment I'm doing nothing as I cannot see that it's logical to >cut it off. You just adjust the upper or lower bound, leave the PV totally alone, and continue searching as though there was no hash hit of any kind. The only thing is you now have a better bound to guide the search... > >All help and suggestions appreciated! > >Regards, > >Steve > >BTW the code is written in Object Pascal / Delphi!
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