[Rivet] Splitting rivet analysis in several jobs

[Piergiulio Lenzi]

Dear Rivet developers,
     I have a rather basic question about aida plots.
Is there a transparent way of combining histograms obtained in different 
runs?
I would like to split my analysis job in several jobs.
I understand that in general it can be tricky especially if 
normalizations are involved.
But I also saw that  a rivet-mergeruns is provided, I don't know exactly 
if this could be used for my task.
Also on a related subject I was wondering how to combine aida plots for 
different subsamples in case of alpgen, for example.

Thanks
Giulio