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Sean: How about attaching a trial counter to each individual so that  
slaves could base the seed on that counter?

- John



On Aug 12, 2008, at 9:03 PM, Sean Luke <[log in to unmask]> wrote:

> 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.
>
> Sean
>
> 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