Author: Roberto Waldteufel
Date: 07:09:32 09/21/98
Go up one level in this thread
On September 20, 1998 at 20:59:55, Robert Hyatt wrote: >On September 20, 1998 at 19:49:57, Roberto Waldteufel wrote: > >> >>On September 20, 1998 at 17:49:17, Inmann Werner wrote: >> >>>On September 20, 1998 at 17:30:31, Robert Hyatt wrote: >>> >>>>On September 20, 1998 at 14:21:15, John Coffey wrote: >>>> >>>>>I think that the subject says it all. >>>>> >>>>>John Coffey >>>> >>>> >>>>Yes. You store the best move when you store a position, assuming you >>>>have a best move (you don't if you searched all moves and failed low, >>>>of course.) You should try this move first each time you encounter this >>>>position... >>> >>>Whats the thing with the fail low? >>>Why can I not use the Hash table for move ordering in this case? >>>(I do now!) >>> >>>Werner >> >>Hi Werner, >> >>When a fail low occurs, there is no guarantee that any of the moves that were >>searched are worth as much as the respective scores they produced (they can't be >>worth more, but could be worth less, maybe a lot less). Thus the move with the >>best score is not necessarily the best move.... >> >>Best wishes, >>Roberto > > >problem is, you don't even get "real scores" of any kind... only an indication >that the score is <= alpha, whatever alpha is... On odd occasions you can get score<=some value that is itself lower than alpha if you use the fail-soft version of alpha-beta, which is useful for the upper bound in the hash table, but this is a fairly rare occurrance. In any event, it is not possible to infer anything about the relative merits of any of the moves from the values they returned if a fail-low occurs at the node. Best wishes, Roberto
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