[Rivet] Dangerous casting to FinalState

[David Bjergaard]

Hi Frank,

For some reason your test works (with the patch): 
> rivet --pwd -a MY_RFSTEST2c zee.hepmc 
> Rivet trunk running on machine calypso (x86_64)
> Rivet.Analysis.Handler: WARN  Analysis 'MY_RFSTEST2c' is unvalidated: be careful, it may be broken!
> Reading events from 'zee.hepmc'
> zfinder: -11 10022
> zfinder: 11 10021
> rfs.size = 8
>   rfs[0] = 2103 10006
>   rfs[1] = 2 10007
>   rfs[2] = 2103 10009
>   rfs[3] = 2 10010
>   rfs[4] = 21 10015
>   rfs[5] = 21 10016
>   rfs[6] = -4 10017
>   rfs[7] = 4 10018
> Finished event loop
> Rivet.Analysis.Handler: INFO  Finalising analyses
> Rivet.Analysis.Handler: INFO  Processed 1 event

> The MCnet usage guidelines apply to Rivet: see http://www.montecarlonet.org/GUIDELINES
> Please acknowledge plots made with Rivet analyses, and cite arXiv:1003.0694 (http://arxiv.org/abs/1003.0694)
> Cross-section = 1.515878e+03 pb
I wonder if its a compiler difference?
> g++ --version
> g++ (Ubuntu 4.8.2-19ubuntu1) 4.8.2
> uname -a
> Linux calypso 3.13.0-46-generic #77-Ubuntu SMP Mon Mar 2 18:23:39 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

Cheers,

    Dave

Frank Siegert <frank.siegert at cern.ch> writes:

> Hi David,
>
> Thanks for your feedback.
>
>> Just thinking out loud:
>> addProjection is templated on a reference, is it possible to make a
>> specialized template for the non-reference version?
>>
>> Something like:
>>     template <typename PROJ>
>>     const PROJ& addProjection(const PROJ proj, const std::string& name) {
>>       std::cerr<<"Please be careful about using references!"<<std::endl;
>>       return proj;
>>     }
>
> But we would not want to prevent *registering* projections by copy,
> since that's in general absolutely fine, right? It's rather the
> copying of a derived projection, e.g. VetoedFinalState, into a
> FinalState that seems dangerous to me.
>
> I have just tested that it's possible to hide the copy constructor,
> and am attaching a patch for Rivet which shows how this would work in
> real life. It's a bit ugly to have to hide this for each derived
> FinalState explicitly, I don't know whether there is any better way to
> disallow such "lossy" copying altogether for a base class?
>
> With this patch Rivet compiles fine, and a few of the typical ZFinder
> analyses seem to work as expected. Furthermore, an accidental VFS ->
> FS copying like in my Example 1 now fails as expected and 2a and 2b
> work as expected. But 2c is a bit strange... it compiles fine, but at
> runtime fails with:
> Error in MY_RFSTEST2c::init method: No projections registered for
> parent 0x7fff33dc1630
>
> I don't at all understand where that's coming from, but there is a lot
> of casting in the projection registration going on. Any ideas? I'm
> attaching a simple analysis that demonstrates this behaviour, together
> with one Zee event for testing.
>
> Cheers,
> Frank