Author: Dave Gomboc
Date: 22:33:35 08/11/99
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On August 12, 1999 at 01:10:14, blass uri wrote: >This example shows that the null move is not a very good idea. >If you need more 3*2=6 plies to see the right move and there is no >zunzwnag(playing no move cannot help black) then you are not close to see >everything to depth n-r with null move. > >I thought depth n when you use null move with R=2 means that except for >zunzwangs you analyse everything to depth n-2 and I see that it is not the case. > >Uri Well, null-move is as you described, but what is shown above is "recursive null-move", which seems to be pretty popular, and some people abbreviate this as simply "null-move". It is the sort of search algorithm that gives people a happy feeling inside about how deep they are searching, but leaves holes for programs like DB to drive a truck through. Of course, Bob has pointed this out more than once before. Consider how much is being chopped out of some 13 ply search, and you might agree that Bob isn't just being stubborn: there's actually quite a big difference in coverage. Of course, those who use recursive null-move are making the reasonable gamble that the extra coverage isn't beneficial at their search speeds. Dave
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