[Rivet] more fun with alpgen

[Gavin Hesketh]

Hi Andy,
I'll have to do more digging to figure out what really happens, but 
here's a bit more info. I use this command:

agile-runmc AlpGenPythia6:423:2.1.3d --beams=TVT:1960 -n 230 -P 
params.txt -o hepmc.fifo &
rivet --analysis=D0_2009_S8349509 hepmc.fifo

The number of events that are read in, pass UPVETO and make it out of 
pythia is only 224. The loop in agile-runmc:


## Make and write events
for i in range(opts.NEVTS):
     st = run.makeEvent()
     logging.debug(run.eventSummary())
     if not st:
         logging.error("Writing events failed")
         break
     if RECVD_KILL_SIGNAL is not None:
         logging.critical("Leaving event loop early due to signal " + 
str(RECVD_KILL_SIGNAL))
         break

gen.finalize()

does loop over 230 (not 224), and gen.finalize() seems to be called. eg 
the end of the output:


AGILe.PYTHIA: INFO  Finalising...
1********* PYSTAT:  Statistics on Number of Events and Cross-sections 
*********

 
==============================================================================
  I                                  I                            I 
        I
  I            Subprocess            I      Number of points      I 
Sigma   I
  I                                  I                            I 
        I
  I----------------------------------I----------------------------I 
(mb)    I
  I                                  I                            I 
        I
  I N:o Type                         I    Generated         Tried I 
        I
  I                                  I                            I 
        I
 
==============================================================================
  I                                  I                            I 
        I
  I   0 All included subprocesses    I          224           488 I 
1.435E-09 I
  I   4 User process 661             I          224           488 I 
1.435E-09 I
  I                                  I                            I 
        I
 
==============================================================================

  ********* Total number of errors, excluding junctions =        0 
*************
  ********* Total number of errors, including junctions =        0 
*************
  ********* Total number of warnings =                           1 
*************
  ********* Fraction of events that fail fragmentation cuts =  0.54098 
*********

HeavyIon input stream invalid line type: 
HepMC::IO_GenEvent-END_EVENT_LISTING
HeavyIon input stream setting badbit.



and now it just hangs (even ctrl-c won't kill it!). The last two lines 
of the output are probably a clue...
If I just run agile-runmc (no rivet) and dump to a file, it exits 
without hanging. The last 6 events in the file are junk though, so 
ideally it would stop when there are no more events to read in rather 
than going for the number I specify at the command line. However, it 
does have the "end event listing" flag:

E 230 -1 -1.0000000000000000e+00 -1.0000000000000000e+00 
-1.0000000000000000e+00 0 0 0 0 0 0 1 1.0000000000000000e+00
N 1 "0"
U GEV MM
C 1.4347291803278606e+00 9.5861875635604679e-02
HepMC::IO_GenEvent-END_EVENT_LISTING

So, I'm not sure what happens.

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
>