Author: Robert Hyatt
Date: 08:13:10 11/21/02
Go up one level in this thread
On November 21, 2002 at 04:52:13, Omid David Tabibi wrote: >On November 20, 2002 at 22:05:29, Robert Hyatt wrote: > >>On November 20, 2002 at 16:55:41, Gian-Carlo Pascutto wrote: >> >>>Nullmove in Deep Sjeng uses an algorithm of my own, but I can >>>switch it back to other systems easily. I did so for running >>>a few tests. >>> >>>I made a version which uses Heinz Adaptive Nullmove Pruning >>>and a version which uses your verification nullmove. >> >>This would seem to be a bit harder than at first glance. They say that >>if the normal null-move search fails high, then do a D-1 regular search >>to verify that, but while in that verification search, no further >>verification searches are done, meaning that the normal null-move search >>fail-high is treated just like we do it today.. >> >>I'm going to experiment with this myself, just for fun, but it seems that you >>need to pass some sort of flag down thru the search calls indicating that >>you are either below a verification-search node or not so that recursive >>verification searches are not done... >> > >Exactly!! (finally someone read the article carefully) > >See Figure 3 for detailed implementation (the flag you mentioned which is passed >down as a parameter for search(), is called 'verify' in the pseudo-code). > >At first stage leave alone the zugzwang detection part (the piece of code at the >bottom of Figure 3). Due to instablilities, some programs might do a needless >re-search. First let the algorithm work fine in general, and then do the >zugwzang detection part. > >I'm looking forward to your results in Crafty... I am working on it. :) It is a bit more complex as I pass a 0/1 flag already that says "do null at next ply or don't do null at next ply". that needs to be modified to a four-state flag, one bit says "no verifications beyond this point" the other says "don't do null move at next ply only". As you might guess I have screwed this up 10 times already and the tree gets real big or real small real quick. (and it is real wrong too).. :)
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