Author: Uri Blass
Date: 05:45:52 06/18/03
Go up one level in this thread
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. Uri
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