Table 1 A list of control parameters of GP for the search of the kernel approximating function.

Population size:

1000

Maximum generation:

1000

Probability of crossover:

0.90

Probability of reproduction:

0.10

Maximum depth for tree created during run:

10

Maximum depth for initial random tree:

7

Terminal set:

{(x_{i 1}, x_{i 2}, ..., x _in ), (x_{j 1}, x_{j 2}, ..., x _jn )}

Function set:

+, -, ×, pow2, pow3, ..., pow10