ctools

When a fits file with zero events in the EVENTS table is passed to ctselect, it throws a RuntimeError, and complains about missing columns from ctselect’s temporary fits file. The example script below, combined with the attached 'noevents.fits’, reproduces this error.

test_script.py:

#!/usr/bin/python
import gammalib, ctools

filename = 'noevents.fits'

obs = gammalib.GObservations()
run = gammalib.GCTAObservation('VERITAS')
run.load( filename )
obs.append( run )

sel = ctools.ctselect(obs)
sel['usepnt'].boolean(False)
sel['ra'    ].real(0.0)
sel['dec'   ].real(0.0)
sel['rad'   ].real(180.0)
sel['tmin'  ].real(0.0)
sel['tmax'  ].real(0.0)
sel['emin'  ].real(   0.3 )
sel['emax'  ].real( 100.0 )
sel.run()

I get the following error:

$ python test_script.py
Traceback (most recent call last):
  File "./test_script.py", line 20, in <module>
    sel.run()
  File "/afs/ifh.de/user/n/nkelhos/scratch/ctools/ctools-git/lib64/python2.6/site-packages/ctools/tools.py", line 522, in run
    return _tools.ctselect_run(self)
RuntimeError: *** ERROR in ctselect::run(): The following columns are missing in the "EVENTS" extension of input file "": "TIME", "ENERGY", "RA", "DEC" 

I break up each 20 minute veritas data run into multiple event lists, so that I can give more precise IRFs to each event list. But, this means that some of these event lists only cover 1-2 seconds of a run, and often won’t have any events, so the EVENTS table will have 0 rows. I’ve encountered this problem at least 4 times in 100 or so runs, so its a fairly disruptive bug.

The error pops up in ctselect::check_infile(), which calls on GFitsTable::contains(), which relies on GFitsTable::ptr_column(), which reads from GFitsTable::m_columns. Beyond that, I’m not sure why GFitsTable::m_columns is empty during ctselect::run().