Author: Ricardo Gibert
Date: 18:16:50 06/19/03
Go up one level in this thread
On June 18, 2003 at 08:45:52, Uri Blass wrote: >On June 18, 2003 at 06:15:41, Thomas Mayer wrote: > >>Hi Uri, >> >>>You need to assume also not using hash tables for pruning. >>>There is an assumption that alpha beta includes no pruning by null move or by >>>hash tables. >> >>my godness, Uri - we are talking about pure alpha beta the hole threat... pure >>alphabeta definitely excludes any type of pruning... > >Ok >In this case it is only a question of definition. > >I think that everybody says that program use alpha beta so I thought that >talking about alpha beta does not mean automatically no pruning. > >> >>>I do not see a reason to make this assumption when most of the programs use >>>pruning and(or) hash tables. >> >>it's simple - that was the question of the initiator of this thread. :) >> >>> The right sentence is: >>> "With perfect move ordering, alpha-beta (with no pruning including not using >>> the hash tables for pruning) has a branching factor of the square >>> root of the min-max branching factor." >> >>wrong, correctly it must be written the following: >> >>> "alpha-beta has a branching factor of the square >>> root of the min-max branching factor." >> >>that's it. Move ordering has no influence at all on the theoretical branching >>factor...For perfect ordering alpha beta would need N(D)=SQRT(Nm(D)) where N(D) >>is nodes in alpha beta of a certain D=Depth and Nm(D) is Nodes with minimax for >>a certain D=Depth... when move ordering is not perfect the practice has shown >>that N(D)=5*SQRT(Nm(D)) is a good approch near to reality to calculate the nodes > > >practise of who? >I never used pure alpha beta(no extensions and no qsearch and no pruning). > >>- the branching factor would not be affected... On first sight this looks >>strange - when you think a little bit deeper about that it is logical - better >>move ordering will bring you a constant speed up which does simply not affect >>the branching factor... > >No It is not logical. >Better order of moves gives exponential speed up. No way! This would imply you can go on improving move ordering forever. Once you have perfect, you have hit a brick wall that cannot be breached. > >Uri
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