Author: Richard Pijl
Date: 00:21:41 09/19/04
Go up one level in this thread
On September 18, 2004 at 23:57:32, Robert Hyatt wrote: >On September 18, 2004 at 18:50:22, Richard Pijl wrote: > >>On September 18, 2004 at 11:28:45, Sune Fischer wrote: >> >>>On September 18, 2004 at 11:09:26, Robert Hyatt wrote: >>> >>>>On September 18, 2004 at 04:05:38, Sune Fischer wrote: >>>> >>>>> >>>>>I decided to try out the triangular PV thing Bob >>>>>speaks so highly of, to see if it improves move ordering... >>>>> >>>>>I was careful to terminate the PV on all exact scores - of course. >>>>>Still I was getting illegal moves in the PV. >>>>> >>>>>It turned out to be a hash/nullmove problem. >>>>> >>>>>See, in the hash I adjust the window down on UPPER bounds, ie. >>>>>something like: >>>>> if (flag==UPPER && score<beta) >>>>> beta = score; >>>> >>>>Are you doing PVS? If so you won't do this a dozen times during a long search, >>>>most likely. But I do this in Crafty as well, and it doesn't _ever_ get illegal >>>>moves in the PV. >>> >>>I haven't looked but I guess you are doing something equivalent to what Richard >>>suggested with beta = score+1. >>> >> >>It may be less important when doing fail-hard. Chances that the upperbound >>equals the real score is lower with fail-hard. >>Richard. >> > >I'm not sure why it would matter. You should fail high, relax the upper bound, >and get the _same_ value back except this time it will be an exact score... >That is pretty normal to get a fail high and then on the re-search, getting the >same score again since the upper bound and true score were identical... Are you doing a research on a fail high in an innernode (when the beta was adjusted)? If you do, you're right. It won't matter. What I meant was, that with fail soft chances are bigger that a stored upperbound equals the true score as it can return a score outside the ab window. >This doesn't cause oddball PVs in Crafty however, even though I see it on >occasion... (see the identical score/upperbound problem, but no illegal moves >in my PV ever). Nor did it ever happen when I used true fail-soft years back... I don't think adjusting bounds will cause anomalies in the PV other than perhaps short pv's (when doing beta=score and no research) as the fail high will truncate the pv. Richard.
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