abstract = "In genetic programming, crossover swaps randomly
selected subtrees between parents. Typically, the
probability of selecting a leaf as the subtree to be
swapped is reduced, supposedly to allow larger
structures on average. This paper reports on a study to
determine the effect of modifying the leaf selection
frequency for subtree crossover on the performance of a
non-standard genetic program. Both a variety of
constant values and dynamic update methods are
investigated . It is shown that the performance of the
genetic program is impacted by the manipulation of the
leaf selection frequency and often can be improved
using a random process rather than a constant value.",