Sure, the slaves can be hacked to ignore the seed given them and  
instead use a seed loaded from a parameter file.  But it's not as  
useful as you'd think.  ECJ's master-slave facility is not  
synchronous, meaning that any slave can be used to evaluate any  
individual, in any order, and take as long as it needs.  This allows  
the facility to be much more efficient, but in turn, it is going to  
make replicability nearly impossible because who knows what slave will  
be asked to evaluate individual X next time around...

If you farm out the evaluations as described below, AND were using  
generational evolution, AND you guaranteed that the slaves registered  
themselves in the same order initially (perhaps  by having one  
register every 5 second -- I made that up just now), yes, I *think*  
you could guarantee replicability, but I'm not positive.


On Aug 12, 2008, at 11:23 AM, David Robert White wrote:

> Hi,
> As I understand, when using Master-Slave evaluation the Master  
> generates a seed from the wallclock and sends it to the slaves.  As  
> a result, the runs are not repeatable regardless of the timings of  
> evaluation by the slaves.  Can I change this so that the slaves are  
> given seeds from their parameter files, or from the Mersenne Twister  
> in the Master?  Please could you let me know the rationale behind  
> the decision to use the wallclock, I know you will have one!
> If we choose to farm out evaluations with max_jobs_per_slave set to  
> M/N (M = pop size, N = slaves), and we had control over the seeds of  
> the slaves, wouldn't we be able to perfectly replicate an individual  
> run?  For me, this would be more important than efficiency  
> (especially considering my slaves are almost identical).
> Thanks,
> David
> -- 
> David R White
> Research Student
> Department of Computer Science
> University of York
> York YO10 5DD
> United Kingdom