[Rivet] Multiple event weights

[Andy Buckley]

Hi Stefan,

For running in ATLAS there is already a hack to use different vector 
entries than the canonical zero-index.

Generally handling full weight vectors through the Rivet chain is a more 
involved process -- at least it is if (as we do) you don't want to have 
to expose repeated loops over weight vectors to the users. We've been 
iterating designs for that -- and the related issue of NLO counterevents 
-- for a long time, and it's not yet finished.

But there is a v3.0.0beta1 tarball that you might find does what you 
want. It just works for Histo1D data objects, but maybe that's enough. 
I'll let David Grellscheid or Chris Pollard comment on the progress 
toward a beta2, which would handle more general analysis objects and 
will generally be more in sync with the current 2.5.x sing-weight 
release series.

Andy


On 27/10/16 14:25, Stefan von Buddenbrock wrote:
> Dear Rivet experts
>
> Looking at the Doxygen page for the Rivet Event class, I see that the
> weight is retrieved as follows:
>
> {
>     return (!_genevent
> <https://rivet.hepforge.org/code/dev/classRivet_1_1Event.html#ab1a3b4bbcb1af136c14405e4c6b4ea4d>.weights().empty()) ? _genevent
> <https://rivet.hepforge.org/code/dev/classRivet_1_1Event.html#ab1a3b4bbcb1af136c14405e4c6b4ea4d>.weights()[0] : 1.0;
>   }
>
>
> There is also a TODO which mentions the possibility of incorporating the
> multiple possible weights from the HepMC file.
>
> My question is: is there any particular difficulty in trying to
> implement this? As far as I can tell, the HepMC::WeightContainer is
> pretty much just a vector of doubles, so I could try and hack the source
> code to get this vector through a new method.
>
> Cheers
> Stefan
>
>
>
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-- 
Dr Andy Buckley, Lecturer / Royal Society University Research Fellow
Particle Physics Expt Group, University of Glasgow