Author: Dave Gomboc
Date: 21:55:05 03/09/99
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On March 09, 1999 at 14:34:49, Will Singleton wrote: > >Using PVS, I can't seem to demonstrate a clear benefit to using a small window >around the root score, as opposed to +-mate. > >Using a window of, for example, one-third pawn, if a move fails-high or low, it >takes fewer nodes to ascertain the move that caused the change, because you >don't have to find the real score right away. But then you've got to resolve >the new score, and that will take more nodes since you've got to re-search with >the relaxed window. In general, it should take you less nodes to search (n, n+1) followed by (n+1, beta) than it will for you to search [alpha, beta]. You are blocking out (alpha, n) completely, that must be worth something if your move ordering is good, yes? >And if, after a fail-high or low, you attempt to delay score resolution until >the next ply (to avoid the re-search at the same ply), it seems you might have >the problem of finding a worse move after the fail at the same ply, since you >don't know the real score yet. This would result in even more nodes being used. You could choose to not resolve the fail-high as long as you don't have a second move fail-high on the window (n+1, beta) as well. If that happens, you'd better resolve one of them, and test the other against whatever result you get from the resolved one. >So I don't see much benefit, unless I'm doing something wrong (likely). On a >normal search, without any fails, I see either more or less nodes (between >windowing and +-mate), depending on the position. But not really much change. > >Any comment would be apppreciated. > >Will I assume your transposition table is working well. Minimal-window techniques (but especially mtd(f), PVS is not so bad) rely heavily on a good tt. Dave Gomboc
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