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Re: Simple analysis example of stdhep files ? [message #1270 is a reply to message #1265] Wed, 07 November 2007 14:29 Go to previous messageGo to previous message
Messages: 16
Registered: June 2007
Location: Fermiliab

Hi Graham,

I see that you already have some examples. I have one comment to add. You should not directly access the stdhep "common block" but should access it via something like the LCIO container of MCParticles ( or its equivalent in other frameworks ). If not you will eventually get caught with the following:

Some of the ILC event files advertised to be in stdhep format are not. They are written in an unofficial extension of stdhep that will cause most stdhep readers to dump core ( or, sometimes, to produce incorrect results). So you must either choose to avoid the bad files or choose your stdhep reader wisely.

Any file that contains more than NMXHEP particles in one event will cause the problem. This happens often in beamstrahlung event files. I have not seen the problem in other files but I can imagine situations that it might. Currently NMXHEP=4000 in the official release.

What readers to use:

The files can be read safely by org.lcsim.

I guess, but do not know for sure, that the code that converts stdhep to LCIO is also safe. Norman can you confirm this?

I do not know about Marlin but I would guess it's safe. Frank do you know?

The files cannot be read by the 4th concept code.

The files cannot be read by the standard stdhep libraries owned by the stdhep maintainers.

If you want to run private C++ code, reading stdhep directly without Marlin or LCIO, you are on your own, at least for now.

You mentioned wanting to use F77. There is no hope for that to ever work unless you make your own private copy of stdhep and compile in a sufficiently large value of NMXHEP.

There are good reasons to allow more than NMXHEP particles per event but this change was made without alerting the maintainers of stdhep so the change never made it to other stdhep readers.

I am aware of a hack that will work around the problem in a confined envirnment but it is not truly robust for use with the full body of legacy code. Any robust solution will require changes to the legacy code: the question is where to require the changes.


Rob Kutschke Computing Division, MS#234 Fermi National Accelerator Laboratory
Phone: (630) 840-5645 P.O. Box 500
Fax: (630) 840-2783 Batavia, IL 60510
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