def fitness_func(X): x = X[:, 0] y = X[:, 1] return x ** 2 + y ** 2 + x

** 3 + y ** 3

This fitness function takes in a 2-dimensional array of solutions, where each row represents a solution with 2 variables x and y. It computes the fitness value for each solution using the formula x^2 + y^2 + x^3 + y^3.

The fitness value represents the quality of the solution, where higher values indicate better solutions. The function is designed to encourage solutions with higher x and y values, as well as solutions that have a balance between the x and y values.

Note that there is a syntax error in the code provided, where the return statement is not properly formatted. The corrected code should be:

def fitness_func(X):
x = X[:, 0]
y = X[:, 1]
return x ** 2 + y ** 2 + x ** 3 + y ** 3