Author: Robert Hyatt
Date: 12:33:33 09/30/98
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On September 30, 1998 at 12:10:44, Don Dailey wrote: > >>>Which is pretty much how I do it. But my main point actually was how >>>one should THINK about null move selectivity. Thinking of it this way >>>is a great simplification and can make it easier to understand. >>> >>>My program actually does a null move search with a zero width window >>>around beta, so I don't actually get to raise alpha. In lots of testing >>>I did this was more efficient, I don't know if anyone else has tried >>>this or finds it useful. I also do my test at the top of the search >>>like you do but after making the move passed to the search function. >>> >> >> >>My null-search is also with beta-1,beta as the window, because I only care >>about failing high, and wouldn't trust the null-move to "raise alpha" in >>those few cases where I am not already doing a null-window search in the >>PVS code. > >Hi Bob, > >I have the same concern. There were a few positions that caused problems >and since the zero window is fast, there seems to be no justification >for having to put up with the alpha problem. > >- Don I thought this was a moot point in your case anyway, since using mtd(f) means *every* node is searched with X,X+1... ??? almost all of mine are searched the same way. This "thinking" probably goes back to the Slate/Atkin days when they talked of using the hash table to "raise alpha" or "lower beta" if the bound wouldn't immediately cause a cutoff. Way before negascout/PVS type algorithms... I Never did this funny-business with hashing, because it never seemed to be 100% safe... each time I tried it I would see fishy things here and there...
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