Author: Tord Romstad
Date: 15:21:28 01/21/04
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On January 21, 2004 at 14:14:00, Robert Hyatt wrote: >On January 21, 2004 at 13:34:27, Tord Romstad wrote: > >>Yes. This is why it is a good idea not to do IID at all nodes, but only >>at nodes where you are reasonably sure that there will be a fail high. >>You should always check the value of the static eval before doing the >>internal search. > >I don't even think you want to do it at fail-high nodes. Just at nodes >where you expect a "true score". At least that is how _I_ have implemented >it. I use MTD(f), hence I *never* get any "true scores" anywhere in the tree. My intuition regarding PVS is not very good (I have used MTD(f) almost since the beginning), but I don't see any reason not to use IID at all expected fail-high nodes in a PVS search, too. At a fail-high node, you can return a value before all moves are searched. If your move ordering is perfect, you will only need to search one move. It therefore makes sense to make some extra effort to make sure that the first move searched will really return a score >= beta, and the most obvious way to do this is to first do a search with reduced depth. What am I missing? Another thing that has always puzzled me is that reducing the depth by only 1 ply gives better results for me than reducing by 2 plies, like you and almost everybody else do. I have tested this very thorougly, and depth-1 always seems to be a bit better. Really weird. Tord
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