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In an attempt to approximate the degree of isomorphism,
we count the number of pseudo-isomorphic trees in the population.
Pseudo-isomorphic trees are represented by the number of similar 3-tuples
in the population, where a 3-tuple is defined as
*# of terminals, # of nonterminals, depth* for each individual.
Two identical 3-tuples
represent trees which could be isomorphic, while two non-identical 3-tuples
represent trees that certainly can not be isomorphic.

S Gustafson
2004-05-20