I'm sorry Daniel, I can't do much here without the full stack backtrace 
printed out, not just the exception.  Can you provide that?

At any rate, nowhere should ECJ be relying on initial population size 
conditions: that would definitely be a bug.  Populations can and do 
resize themselves: in fact I have an entire paper relying on that fact. 
  (http://www.cs.bham.ac.uk/~wbl/biblio/gp-html/luke_2003_gecco.html) 
And the ES package does it as a matter of course.

Sean

Daniel Lombraña González wrote:
> Hi to all,
> 
> I'm trying to use ECJ with GP and dynamic populations. I have been
> searching in the mailing list and I found the following conversation:
> 
> https://listserv.gmu.edu/cgi-bin/wa?A2=ind0404&L=ECJ-INTEREST-L&P=R72&I=-3
> 
> I have tried that solution, but I get an error when the
> CrossoverPipeline tries to create two new offsprings. The obtained
> error is the following one:
> 
> Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 18
> 
> It seems that the variable "q" is getting out of the bound in the inds
> array. I don't know how to fix this. It seems that the problem relies
> on the initial population length = 20, which is not varied at all
> during the evolution.
> 
> Any ideas?
> 
> PS: By the way, if using the proposed solution you increase the size
> of the subpopulation you get an error because ECJ tries to compute the
> fitness of a null individual :)
> 
> --
> ··························································································································································
> PhD Candidate
> Cátedra Ceta-Ciemat de la Universidad de Extremadura
> http://gea.unex.es/catedra-ceta-ciemat/
> Universidad de Extremadura
> ··························································································································································
> Por favor, NO utilice formatos de archivo propietarios para el
> intercambio de documentos, como DOC y XLS, sino HTML, RTF, TXT, CSV
> o cualquier otro que no obligue a utilizar un programa de un
> fabricante concreto para tratar la información contenida en él.
> ··························································································································································
> 
> 
>