Hi,

I encountered a case where, if I'm using roulette wheel selection or stochastic universal selection and if the fitness sum is 0, there will be a division by 0. I know that probably it's very little probability to encounter such a case, but my suggestion would be to instead of havingprobs = fitness / fitness_sum
to have:

iffitness_sum!=0:probs=fitness/fitness_sumelse:probs=0

or instead of probs=0, to divide fitness by a very large number.

Best Regards!