Author: Robert Hyatt
Date: 19:23:18 09/11/99
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On September 11, 1999 at 15:59:19, Ed Schröder wrote: >On September 11, 1999 at 15:36:18, Robert Hyatt wrote: > >>OK... then we are 'in sync' here it seems.. >> >>As far as PVS, the main advantage is that since almost everything is searched >>with a null-window, it saves nodes, _IF_ you do well at move ordering (I have >>no doubt that you do well so PVS might be a win for you too)... >> >>It reduced my trees by 10% and loses nothing at all... unless you screw >>up move ordering, then it can make the tree bigger as you first search with >>a null window, then you have to re-search with the normal window... > >Thus, PVS is aspiration search with a null-window? Is that all there is? > >Ed basically yes. You search the first move at any ply with the window that is passed in. You search the remainder of the moves with alpha,alpha+1. And all you care about is the case where another move comes in >= alpha+1, because then you have to re-search that move with the original window. Of course, 99.99999999999% of the time, the window passed in is x,x+1, so this doesn't happen... It is very efficient, since it is a more controlled version of mtd(f) when you think about it. IE mtd(f) inside the tree, but not along the PV...
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