Author: Robert Hyatt
Date: 07:02:23 12/28/99
Go up one level in this thread
On December 28, 1999 at 01:38:49, William Bryant wrote: >I looked at this a year ago, but want to again ask the best way to handle >this situation. > >You fail high at the root, > increase alpha to beta -1 > increase beta to Mate (or Mate - 1 depending upon how these are defined) >Then you fail low on the same move. > >What I have been doing is accepting the fail high as correct, > making this the PV move, > and continuing the search at the next iteration with > a window set around alpha which is the old beta -1, + or - the aspiration > window size. > >Is this correct, is there a better way to handle a fail high/low. > >Thanks > >William >wbryant@ix.netcom.com I have two cases. (don't forget I use PVS). 1. get a value for first root move as normal, then a later move fails high on the null-window search, but when I re-search with the normal PVS window, it now fails low. I pretend the fail high didn't happen and keep the original root move. 2. A root move fails high, but then fails low on the re-search. I keep the fail-high move. You can probably eliminate the fail-low by simply searching with -inf,+inf, but it will be slower, and due to hash overwrites/draft problems this fail-high/fail-low problem will happen without this large window. And with the large window you might fail high on bound X, but get a score back that is < X... It is mainly an artifact of null-move search and hashing...
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