Author: Robert Hyatt
Date: 12:47:05 05/06/04
Go up one level in this thread
On May 06, 2004 at 15:32:11, Dan Honeycutt 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... :) > >Are the there known implications on the search from doing using fail-soft vs >fail-hard? From a tiny amount of testing it looks like my engine does best >using a fail-soft (outside the window) lower-bound (returning beta) and a >fail-hard (inside the window) upper-bound (returning alpha). I'm sure I have >something backward in that last sentence - see my reply to Anthony below for >what I'm trying to determine. > >Thanks. >Dan H. No problems I am aware of. With PVS it doesn't matter much since almost all searches are done with a null-window...
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