abstract = "This paper introduces a random tree generation
algorithm for GP (Genetic Programming). Generating
random trees is an essential part of GP. However, the
recursive method commonly used in GP does not
necessarily generate random trees, i.e the standard GP
initialisation procedure does not sample the space of
possible initial trees uniformly. This paper proposes a
truly random tree generation procedure for GP. Our
approach is grounded upon a bijection method, i.e., a
1-1 correspondence between a tree with n nodes and some
simple word composed by letters x and y. We show how to
use this correspondence to generate a GP tree and how
GP search is improved by using this randomness",