Author: J. Wesley Cleveland
Date: 08:17:35 08/27/04
Go up one level in this thread
On August 26, 2004 at 21:00:10, Robert Hyatt wrote: >On August 26, 2004 at 14:09:06, Bert van den Bosch wrote: > >>On August 26, 2004 at 11:33:48, Robert Hyatt wrote: >> >>>On August 25, 2004 at 17:37:59, Bert van den Bosch wrote: >>> >>>>First of all, I hope the forum will continue in some way! >>>> >>>>Before it is gone, I have a question. >>>> >>>>I wanted to check my null move so I tested if the null move would create a >>>>cutoff, and after that I did the normal stuff. So if you have a cutoff with null >>>>moving you are almost sure you will also get a cutoff with the normal proces, >>>>except for zugzwangs of course. But this wasn't happening all the time when I >>>>tested it, and usually the values involved from what I got back from nullmove >>>>and from the normal process were just a few centipawns in difference. Could this >>>>be because of search instabillity? If it isn't a bug in my program I had the >>>>idea to search nullmove with beta-MARGIN in order for the value returned by null >>>>move to bridge the few centipawns gap. And taking MARGIN the few centipawns. But >>>>I'm not sure if that is correct. Can someone shine a light on this? >>>> >>>>Thanks, greetings Bert >>> >>>This isn't what null-move is about. It will fail high in positions where a >>>normal search won't, but that doesn't make it wrong. The point is that if your >>>opponent can move twice in a row and you fail high after "passing" then your >>>position is very good and it is safe to avoid searching to the normal depth to >>>see if it is even better. >>> >>>As a general rule, if null-move fails high, a normal search should also fail >>>high, of course, as that is the point in that the null-move search is easier to >>>do since it searches to a reduced depth. But there is nothing to say that if >>>the null-move search fails high that the regular search will not, that is part >>>of the risk you take, since null-move is not 100% accurate. Reduce the depth >>>and you obviously will miss some tactical shots that the deeper depth would not >>>miss. >>> >>>If you want an "error-free" pruning algorithm, good luck. Logic says no such >>>thing exists. :) >> >>alphabeta :) > > >OK. > >If you want an error-free _forward-pruning_ algorithm, good luck. Logic says no >such thing exists. :) EGTBs ;)
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