[Rivet] more fun with alpgen

[Gavin Hesketh]

...if you are interested in reproducing it exactly, this is the output 
from agile-runmc:

http://www-clued0.fnal.gov/~ghesketh/hepmc-crash.txt

then just:
 > rivet hepmc-crash.txt

should do it. I suspect it's a HepMC IO problem, as the last event (for 
which there was no input) has no P or V, so probably the 
"END_EVENT_LISTING" is not parsed correctly.

cheers,
	Gavin

On 16/12/10 17:04, Andy Buckley wrote:
> On 16/12/10 16:39, Gavin Hesketh wrote:
>> Hello,
>> hopefully a simple one.
>>
>> I'm running alpgen+pythia using agile, piping into a fifo being read by
>> rivet. I  specify the number of events: agile-runmc -n 1000.
>>
>> The problem is pythia is reading from an external file (from the alpgen
>> matrix element generator), which might not contain 1000 events. Then,
>> pythia calls UPVETO, to veto events based on parton-particle jet
>> matching. So, even if the external file contains 1000 events, they might
>> not all get processed through pythia to make it to the fifo.
>>
>> The result being that rivet does not get 1000 events, and just hangs
>> once the fifo is not being filled. I have to kill it by hand, which
>> means no .aida file, and no way to run this on the batch queue...
>>
>> Now, I have no way of knowing in advance exactly how many events will be
>> in the external file read by pythia, or how many of those will fail
>> UPVETO. So I want to tell agile to run over as many as possible (it
>> seems to cleanly stop once the external file is exhausted, even if this
>> is less than the "n" I specify). But is there a way to make rivet wrap
>> up cleanly once the fifo is not receiving any more events (or when agile
>> is no longer running)?
>
> Hi Gavin,
>
> Are you telling rivet to expect exactly 1000 events? In that case I
> think it will wait even when AGILe has died. It should exit cleanly,
> with an output file, if Ctrl-C'd. And if you don't specify a number of
> events to Rivet, it should run until the end of the HepMC stream, which
> is written by AGILe shutting down correctly. Maybe the AGILe AlpGen
> interface *doesn't* exit smoothly enough to write that terminating run
> footer.
>
> Without having time right now to look into it, I think that Rivet is
> doing the right thing, and heuristics to guess when the fifo is not
> receiving more events would probably have their own edge cases and
> problems. I've put a 1 hour timeout on the first event into the SVN
> version of Rivet, to catch a never-amusing batch farm gotcha where jobs
> appear to be running for days but are actually doing nothing at all, but
> even if I were to extend that to the event loop it wouldn't have the
> sort of responsive behaviour that you want.
>
> So the problem is probably either that agile-runmc is *not* exiting as
> smoothly as required when the external file is exhausted, or that you
> are explicitly telling rivet to wait for a fixed number of events which
> never arrive. Which is it? If the former, we should fix that before
> making the next AGILe release (pretty soon, I hope)
>
> Andy
>