Michael Hart wrote:

> Not sure where the best place for bug reports is, but basically 
> InterPopulationExchange doesn't work in checkpoints because the inner 
> class IPEInformation doesn't implement Serializable.
> Adding "implements Serializable" seems to work fine (not extensively 
> tested, but the checkpoint will write and I can restart from it).

I believe that's all.  If you also declare it static:

	    static class IPEInformation implements Serializable

... you can also avoid having to explicitly provide SerialVersionUIDs.