Author: David Rasmussen
Date: 07:54:04 01/06/01
Go up one level in this thread
On January 06, 2001 at 10:20:38, Robert Hyatt wrote: >On January 06, 2001 at 06:45:52, David Rasmussen wrote: > >>On January 05, 2001 at 23:48:58, Robert Hyatt wrote: >> >>>>> >>>>>One problem if you do null-move, is to watch for cases where a root move fails >>>>>high, then fails low on the re-search. In that case I do _not_ make that move >>>>>a PV move. >>>> >>>>What do you do then? >>> >>>OK.. let's take the root. The first move is searched. I then use the PVS >>>null-window on the remainder of the ply=1 moves. If one fails high on the >>>null-window search, I re-search with the correct PVS beta value. If this >>>search fails low, I pretend the fail-high didn't happen and keep right on >>>searching without replacing the PV move. >> >>I don't understand. Isn't that the normal way of doing things? I mean, you >>search with a null-window. You get a fail-high, that is the score is larger than >>alpha+1. Then you research with the full window, as always in PVS. Then the >>result of THIS search is the on that counts, right? So if this one fails low, >>then why would you ever replace the PV move? > >What do you do if the null-window search fails high and then you run out of >time? Normally a fail-high causes a PV change. I special-cased this to not >happen on the null-window search unless the relaxed beta bound search confirms >that the fail-high was real. > > Oh. But I just considered the "search and possible research" as an atomic block, and I only update _after_ all this. I never changed the PV after a null-move fail-high. I didn't know others did :) > >> >>>If it fails high on the re-search, >>>It does become a PV move even if it then fails low on the 4th re-search... >>> >> >>Again, isn't this just the way PVS is? >> >>>The bad case is failing high on the null-window search then failing low on >>>the first re-search... that can make you play lemon moves... >> >>I don't understand this at all.. :) > >Most implementations cause _any_ fail-high to place that move first and make it >a PV move, instantly. That can cause problems here... I see. Well I don't.
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