Author: rasjid chan
Date: 19:13:37 05/06/04
Go up one level in this thread
On May 06, 2004 at 15:23:30, Gerd Isenberg wrote: >On May 06, 2004 at 15:05:15, Robert Hyatt wrote: > >>On May 06, 2004 at 14:31:08, Gerd Isenberg wrote: >> >>>On May 06, 2004 at 11:58:11, Robert Hyatt wrote: >>> >>>>On May 06, 2004 at 11:38:44, Dan Honeycutt wrote: >>>> >>>>>Yet again I apologize for asking a question which I'm sure has been asked many >>>>>times before, but could someone explain the difference between a fail-hard and a >>>>>fail-soft and how does is affect a PVS search? >>>>> >>>>>I made the guess that, ie, if (score >= beta) if I return score it's a fail-hard >>>>>and if I return beta it's a fail-soft. It would seem that what I return doesn't >>>>>so much matter as what I put in the hash table. If I put in the (possibly) >>>>>higher value of score then I have a higher lower bound and a greater chance for >>>>>a hash cut if this position arises again. >>>>> >>>>>Thanks in advance. >>>>>Dan H. >>>> >>>>That is backward. But you have the right idea. Fail-hard never returns a value >>>>outside the initial alpha/beta window. Fail-soft does. >>> >>>I often confuse this hard/soft definitions too - i have the wrong mnemonic >>>trick. Intuitively i found it harder if i jump outside a window ;-) >> >> >>It is just as intuitive as where you store a lower bound but flag the position >>as an UPPER bound position. Makes sense after a lot of thought, but it still >>leads to confusion... :) > >yes, but that seems more logical to me than the fail-soft versus fail-hard >issue. To store the lower bound alfa if your score is less or equal to it, hence >score is an upper bound, it could be lower. > >But i never understood why returning values outside the window is soft. The 2 end limits are FIXED, hash/returned at FIXED limits == hard. Soft means swaying about the ends == soft. Rasjid
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