Author: Ernst A. Heinz
Date: 01:39:59 10/21/98
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On October 20, 1998 at 20:33:27, Robert Hyatt wrote: > >On October 20, 1998 at 08:20:53, Ernst A. Heinz wrote: > >>On October 20, 1998 at 08:08:23, Robert Hyatt wrote: >>> >>>Quite easy. With alpha/beta the only "order" we have is (1) best move and >>>(2) rest of moves. There is no "order" to the moves other than one move is >>>better than all the rest. No idea how much better, no idea where the other >>>moves rank with respect to each other... >> >>In order to avoid wide-spread confusion, I would like to add that Bob's above >>statement implicitly assumes "alpha-beta" to mean "PVS/NegaScout" as employed >>by most chess programs. >> >>Pure alpha-beta without null-window searches and eager resolution of any >>fail-high/fail-low situations can of course calculate accurate search scores >>of all moves. But it would be horribly inefficient as compared to PVS (yet >>still much better than naive minimax). >> >>=Ernst= >No "pure" alpha/beta can do this. But if, at the root, you simply reset >alpha/beta after each root move, you get a score whether it be from a PVS >search a negascout search or a traditional alpha beta Right, that is exactly what I said -- so we agree on this. :-) It is not alpha-beta that hinders the calculation of accurate search scores. Instead, the null-window searches which represent the heart of PVS are the real culprits. If you remove the null-window searches and resolve any fail-high/fail-low at the root you can easily calculate the accurate search scores of all moves. Exactly as I said. >(I don't see what null- >move has to do with this issue at all). Where did you read "null move"? I wrote "null-window search" ... :-( =Ernst=
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