3 Experimental Details

A target string of length 63 is generated from $S=[A,B,C,D]$. A target tree structure is constructed with 63 nodes. Tree initialisation is bounded with minimum depth of 2 and maximum size of 4, and subtree crossover is bounded to trees with a maximum depth of 10. Experimental parameters are found in Table 7.1. The target tree is shown graphically on the lattice in Figure 7.2, where the deepest node is at depth 6. This target tree structure defines the following string (resulting from a breadth-first traversal over the nodes (`n') and leaves ('l')):

n n n n n n n n n n n n n n n n n n n l l n l n l n n n n n l n l n n l n l n l l l l l l l l l l l l l l l l l l l l l l l l

The randomly generated target string using 63 symbols, realised over both leaves and functions, is:

C B C C C D B D A D A D B D D D D B C D C A B B D C A D C D B D C C B B B C D A D D C B D D A B C D C A D C B A D D C A B D A

Table 7.1: Experiment and problem parameters for the Tree-String experiments.

Population size	500
Tree initialisation	Ramped half-n-half
Maximum generation	51
Functions (binary)	A, B, C, D
Terminals	A, B, C, D
Other parameters	same as Chapter 4 parameters