Author: Robert Hyatt
Date: 07:44:22 01/22/02
Go up one level in this thread
On January 22, 2002 at 03:18:42, José Carlos wrote: >On January 22, 2002 at 01:53:53, Uri Blass wrote: > >>On January 22, 2002 at 00:44:53, Robert Hyatt wrote: >> >>>On January 21, 2002 at 14:27:34, David Rasmussen wrote: >>> >>>>On January 21, 2002 at 10:41:39, Robert Hyatt wrote: >>>> >>>>> >>>>>You have to do two things: >>>>> >>>>>1. If you get a fail high at the root on a zero-width window (any move after >>>>>the first move should be searched with a zero-width window) you can't trust it >>>>>unless you re-search it with a bigger beta bound and make _sure_ that it doesn't >>>>>then fail low. Such fail-high (zero window) fail-low (non-zero window) is an >>>>>artifact of null-move and if you play such a fail high move even if it fails low >>>>>on the re-search, you will die... >>>>> >>>> >>>>If you mean, do I count value >= alpha+1 from zero-window search as a fail high, >>>>then no. In that case, I research with the original alpha;beta window. Isn't >>>>that ok? >>>> >>> >>> >>>What if you run out of time? You failed high on the null-window search. >>>You started a new search with a wider window and time expired. Do you play >>>the fail-high move or stick with the previous best move? I stick with the >>>last verified move. >>> >>>Unless I fail high a second time which means the original aspiration window >>>was too small and I am now going to +infinity. I trust the second fail high >>>but not the first. >> >>Does it mean that even if the evaluation before the fail high was mate against >>youself you are not going to play the fail high move if you have not time to >>verify it? >> >>In this case it is a mistake. >>It seems better to have a rule based on the previous evaluation when to play the >>fail high move that you cannot trust and when not to play it and not to play it >>only when the evaluation is bigger than some number. > > If the previous pv score is a mate against you and the move you're searching >isn't, it's gonna fail high very quickly in the research. > But I find your idea senseful. For example, if your pv fails low down to >-mate in n and you run out of time so much that you can't allocate more time, >you could even pick a random move among the others, and hope it's not -mate... > > José C. I think that is bad. Remember, you searched for a good while and until the last iteration, your program thought the current best move was really the best one. That means that busting this move is very difficult. Against a human it is very likely that he won't even see how to bust it. If you go belly-up and play a random move, you will greatly increase your chances of really losing this game. (this was discussed by Hans Berliner years ago. It was his idea to behave as I explained). > >>I have no idea about the exact number and looking at positions when Crafty did >>not play a move that fail high may help to get a better idea. >> >>Uri
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