Author: Robert Hyatt
Date: 07:15:27 09/24/99
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On September 24, 1999 at 08:14:05, Bas Hamstra wrote: >What are good ways to control extensions? I like the idea of extending part of a >ply, but am not sure how to implement it. > >Suppose you have a depth 5 to search. Then if you wanted to extend 1/2 ply then >there are now 2 available extensions. You extend here. Next ply: depth=4. How >many available extensions? At first I thought 4/2 = 2, but already used 1, so 1 >left. But I think this is not quite correct to subtract "history" extensions >from the available extensions this ply. But how else??? > > > >Regards, > >Bas Hamstra. First, for simplicity, lets count plies by 100. So a five ply search starts with a depth of 500. For every ply you advance into the tree, you decrement this by 100. So it works as always and the *100 doesn't do a thing, yet. But now we extend by 3/4 ply, say (for some reason at the root of the tree) so our depth is now 575. This does nothing (yet) as when depth drops to < 100, we treat it as zero. So we are still doing a 5 ply search. But _if_ we extend by a fraction of a ply at another point in the tree, 575 + 75 = 650 and _now_ we are really doing a 6 ply search, not 5. But notice how it took two extensions at two different plies, to make this happen? Which lets you sort of say "if something interesting happens at two different nodes in the same path, then I will extend that deeper than if something interesting only happens one time in a path..."
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