I just started running into issues with two breed threads and  
ESSelection when mu+lambda are equal and not even (ie, mu = lambda =  
13). Basically the parent index was one higher than it should be and  
an ArrayIndexOutOfBoundsException was being thrown.

I started digging around the code and I think may  
require a little TLC. Firstly, the produce(int, EvolutionState, int)  
method seems to use a different way of calculating the parent than  
either the breeder or the other produce method does. Secondly, I think  
there's an off-by-one error in the way the current position is  
determined when multiple threads are involved and lambda is not even.

I've attached a couple of patches that I think do the right thing (the  
breeder patch is just a clean-up to clarify the code a little).