Author: Robert Hyatt
Date: 05:40:19 12/14/00
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On December 14, 2000 at 06:50:45, Steve Maughan wrote: >My program doesn't use fail soft atr the moment but I have been reading about it >on the web. I hadn't realised that with fail soft the score, if less than >alpha, is an upper bound and if greater than beta is a lower bound. I can see >that this would be useful - but how useful is it in practice? > >A couple of things I can think of doing if this is the case: > >1) Back up the hash score with the returned value as the bound and NOT alpha or >beta. This would give more hash cutoffs but is it accurate when one has null >move & futility pruning etc? > >2) Use the score as a better bound for a fail high - obvious but I can't see >anyone doing it. As an example Shredder 5 seems to fail high at +0.25 above >current score then +0.50 above current score. Surely if this fail soft property >is robust there must be a better way. > >Are all of these insights correct? > >Regards, > >Steve Maughan It does work (fail soft). But with PVS, it is probably not as effective as it is when used with mtd(f) approaches. There is no way really, to "tighten the bound" in PVS... since the window is almost always a null window (x,x+1).
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