[Rivet] Running Rivet on the grid

[Andy Buckley]

Frank Siegert wrote:
> I have a few suggestions for the grid run strategy, which mainly appeared 
> when I started building the validator:
> 
> We should adapt the downloaded grid-tarballs more to which generator is 
> being run. Is Genser available on the grid nodes? I assume no

If run under the Atlas VO, Genser will be available. I'm not sure about
Pheno.

> Do you think it is feasible to link AGILe at runtime (if found in 
> LD_LIBRARY_PATH) instead of compile time? Since we have identified all 
> relevant places with an "#ifdef HAVE_AGILE" already, this might not be so 
> hard? Of course, during compilation one would need the AGILe headers 
> anyways. If nobody has a better suggestion, I could look into this. 
> Another option would be providing two Rivet tarballs, one compiled with 
> AGILe, and one without.

The new interfaces that I've been working on a bit in the last week
completely do away with using AGILe programmatically. Instead you run
AGILe to dump HepMC events to a FIFO (or an unnamed pipe, once I've
worked out how to handle arbitrary file descriptors) and then run
rivet's interface to read from the same pipe. If sockets have something
to offer, then I'm happy to add support for them, too. There's no Rivet
dependency on access to AGILe, and other generators like Sherpa can do
it without needing to use AGILe at all (although this then loses the
uniform way to pass parameters).

> And as far as I know there is already a mechanism in AGILe which checks 
> and enables only the generator interfaces it can find in LD_LIBRARY_PATH, 
> right?
> 
> Then we can split up the downloaded packages into
>  - HepMC*
>  - LHAPDF*
>  - FastJet*
>  - (boost is not needed, because we only use header files AFAIK)

Correct.

>  - Rivet
>    + libgsl.so link (from what i have noticed, this is missing on SL4,
>      but might only be needed during compilation?)

It's used in the sphericity calculator to diagonalise the momentum tensor.

> All of these should untar into the same temporary bin/ lib/ share/ 
> directories on the grid node, so with a properly set PATH and 
> LD_LIBRARY_PATH all programs can figure out what is available.
> 
> Does that sound reasonable?

Yes. For now I would use the AGILe version of Rivet only, since it keeps
things simple, and anyway the download size of the AGILe library is
pretty small: about 1MB.

Andy

-- 
Dr Andy Buckley
Institute for Particle Physics Phenomenology
Durham University
0191 3343798 | 0191 3732613 | www.insectnation.org