Author: Uri Blass
Date: 13:50:26 07/13/01
Go up one level in this thread
On July 13, 2001 at 14:25:23, Robert Hyatt wrote: >On July 13, 2001 at 12:28:01, Steve Maughan wrote: > >>I'm thinking of implementing double null move in my program. Now as far as I >>know the most conventional way is to do the normal null move search and if there >>is a cutoff follow it with a normal search at reduced depth to confirm no >>zugwag. However I do remember that someone here (Vincent?) outlined a different >>way of doing double null move. Is there another way? If there is, what are the >>pros and cons of each? >> >>Thanks, >> >>Steve > > >That's the gist of it. If the position is a zugzwang position, the second >null-move search will fail high, which will cause the first to fail low and >you don't run into the zug problem. > >The downside is the cost. The second null will fail low most of the time and >just generate wasted nodes. > >The other downside is that not all null-positions are zugzwang problems. In >fact, most null-move problems are caused by the R-value which bring the horizon >too close to spot a tactical threat. Double null won't find any of those... > >So you expend quite a bit of effort, to eliminate one small part of the total >problem... If you search to clearly reduced depth(for example before normal search with null move pruning to depth d when d>=6 you search without null move to depth d/2-2) then you may be less than 1% slower. I believe that it is a good deal to be 1% slower in order to avoid not seeing simple zunzwangs. I guess that you may earn 3 elo from not falling in some zunzwangs and lose only 1 elo from being slightly slower. Uri
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.