Author: Uri Blass
Date: 10:06:28 10/04/01
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On October 04, 2001 at 12:21:07, Sune Fischer wrote: >On October 04, 2001 at 10:19:33, Uri Blass wrote: > >>>Move ordering has that bit of randomness about it, sometimes you pridict wrong >>>and you get the right move second (or even last). >>>Most of the time you would get the right move first though (or else just reverse >>>move ordering, so that is a safe assumtion). >>>Example: >>> >>>1. move has 60% chance of being the best. >>>2. move has 30% chance of being the best. >>>3. and rest 10% >>> >>>Search move 1 => succes has 60% chance. >>>Search half move 1 and half move 2 in the same time => 0.5*(60+30)=45% chance. >>> >>>It will not pay off on average, only once and a while. >> >>It is not so simple. >>programs do not have exact scores for a lot of moves and they search for good >>enough moves and not for the best moves. > >Are we talking about the alpha-beta algorithm here? >The better the move ordering you have, the more cut-offs you get and the faster >you go, so you want the best moves to be searched first. This is exactly the point I want the best move to be searched first. If move A is leading to a forced checkmate and move B is leading to win a pawn then one processor may always start from winning a pawn and decide that winning a pawn is good enough when 2 processors may find the mate,remember the mate, and always start from the mate in every iteration. >You can reverse the whole move ordering, it will end up finding the same move >(or some with equal score) but it will be alot slower, worst case would be >minimax speed. >I don't know what the parallel version of A-B() does either, but I figured it >was something along those lines. > >>if 2 processors search for a good enough move then it is possible that they can >>find in small part of the cases better good enough move than one processor and >>later in the next iterations the computer can remember that better good enough >>move to get a better branching factor. >> >>Uri > >Yes, "in small part of the cases" agreed, but not on average. > >-S. These small part of the cases may be important to get better branching factor because the program is going to reject losing moves for the fact that there is a mate in 1 and not for losing a pawn. Uri
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