[Rivet] more fun with alpgen

[Gavin Hesketh]

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)?

cheers,
	Gavin