Author: Ian Kennedy
Date: 04:40:11 04/06/03
Has anyone done this in their program? I have been trying recently. One of the
problems is that the standard formula for the size of a minimal tree assume a
fixed branching factor. I've manually worked out what the figures are for a
branching factor bf[depth] for the first few plies but gave up after that. I've
just read a paper by Schaeffer in which he refers to a technique suggested by
Carl Ebeling but the book 'All the right moves' in which it appears is now out
of print and Schaeffer doesn't describe the method himself. He quotes some
performances around 1.2x to 1.5x bigger than minimal (2.2 for Belle), does
anyone have any figures for their programs they can share?
Or does anyone have a useful general formula for the size of the minimal tree
based on a varying bf[depth]?
The figures I obtained during a game with my program playing both sides,
averaged over the first 18 b/w moves were
ply 3: 1.21x minimal
ply 4: 2.48x minimal
These actually look very similar to the graph in fig 1 - derived from Phoenix
-in Schaeffer's paper ('New Advances in alpha-beta searching'). And yet my
program looks like it doesn't order and prune as well as others and spends
proportionally longer searching the moves 2-n at each iteration than others.
Ian
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