Author: Don Dailey
Date: 11:52:20 06/22/98
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On June 22, 1998 at 13:35:02, Roberto Waldteufel wrote: > >Hi Guido, > >It seems I had misinterpreted Negascaout. Perhaps my misinterpretation even >constitutes a new variant of this family of search algorithms. My metod on each >iteration is as follows: > >At each node, I search the first move with window {alpha,beta): > >value=-Search(-beta,-alpha,depth-1) >If value>alpha then > If value>=beta then > Search=value > Exit > End If > Alpha=value >End if > > > >Then, if I did not get a beta cut-off, for each subsequent move from that node I >do a null width search, with a research if necessary,like this > >value=-Search(-alpha-1,-alpha,depth-1) I think you really mean this: value = -Search( -alpha, -(alpha-1), depth-1 ) or value = -Search(-alpha, -alpha+1, depth-1 ) >If (value>alpha) and (value<beta) then > value=Search(-value,beta,depth-1) >End if > >If value>alpha then > If value>=beta then > Search=value > Exit > End If > Alpha=value >End if > >This was my interpretation (or misinterpretation) of Reinfeld's pseudo-code. To >be more precise, I search to depth instead of depth-1 if the side to move is in >check. Compared to classical alpha beta with infinite window, it was a great >improvement. I'll have to look at Reinfeld's code again a bit more closely, but >my method seems to work so well that I would need to be really convinced before >recoding it all over again. Do you think I could improve my speed with a proper >PVS? Maybe I waste a lot of time searching the first move to full width instead >of with a null window. > >Best Wishes, > >Roberto This is exactly the way I understand negamax. You can put a window on the first move but I have not found this to be useful although others have reported it to be a gain. - Don
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