Author: Thomas Mayer
Date: 03:15:41 06/18/03
Go up one level in this thread
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... >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 - 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... Greets, Thomas
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