Author: Dan Honeycutt
Date: 12:39:15 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. I obviously didn't know it was soft till a short while ago. Inside the window sounds like "in the comfort zone" or something soft. Outside the window sounds like "out in the wild" or something hard. I'll remember it easily from now on since it's simply backwards from what I think it sounds like. Dan H.
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