Author: Robert Hyatt
Date: 08:47:08 05/11/98
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On May 11, 1998 at 10:20:27, Vincent Diepeveen wrote: > >On May 11, 1998 at 09:06:05, Guido Schimmels wrote: > >>>The only addition I would make to this report is a remark on the odd >>>nature of the PV for Qb6 at ply 10. GM Ronen Har-Zvi pointed out to me >>>that the move Qa7 in this PV is a simple blunder. How such a move can >>>appear in a PV is just one more mystery. >> >>The DB outputs of game 2 you've presented here, have already been >>discussed >>in an issue of the german magazine "CSS" quite some time ago. >>The author says, DB does not propagate the PV from the leaves to >>the root, as most PC-programs do. In order to save time, DB simply >>looks up the PV in the hashtable, which he thinks explains for some >>weird PV's. > >I'm doing this to: i only look in the hashtable. You get exactly >the same PV. the 2 advantages are: > -it is faster > - sometimes you get a little longer PV because of transpositions that > extend your PV. >>Guido No you don't get "exactly the same PV". Often you get one *much shorter* because a critical PV node was overwritten by something that was searched later. That is *the* problem with using the TT for PV moves... Unless you either search very slowly or have a huge TT so you never have to replace anything... Backing it up from the tips is much more reliable, but DB can't do this because the hardware doesn't have a way to pass back a variable amount of information.. just best move and best score... The software search can back up a PV, but when they hit the hardware part, it stops...
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