Hi Olivier,

I tried the patch you provided for the same problem and got the following: 


[xutao@localhost various]$ patch lhe_parser.py empty_file.patch 
patching file lhe_parser.py
Hunk #1 FAILED at 173.
Hunk #2 succeeded at 229 (offset -4 lines).
Hunk #3 succeeded at 252 (offset -4 lines).
Hunk #4 succeeded at 2597 (offset -4 lines).
1 out of 4 hunks FAILED -- saving rejects to file lhe_parser.py.rej


There seems to be something wrong at line 173. So I modified it myself by adding


         if path.endswith('.gz') and mode == 'w' and\
                                               isinstance(self, EventFileNoGzip):
             path = path[:-3]


Then I made a simple test by performing PS in p p > j j process with matching, but got the following errors:


INFO: Running Pythia8 [arXiv:1410.3012] 
No user-defined value for Pythia8 parameter 'JetMatching:nJetMax'. Setting it automatically to 2.
Splitting .lhe event file for PY8 parallelization...
Command "generate_events run_01" interrupted with error:
IOError : [Errno 2] No such file or directory: '/home/xutao/HEP/MG5_aMC_v2_5_5/bin/PROC_sm_1/Events/run_01/unweighted_events.lhe_0.lhe.gz'
Please report this bug on https://bugs.launchpad.net/mg5amcnlo
More information is found in '/home/xutao/HEP/MG5_aMC_v2_5_5/bin/PROC_sm_1/run_01_tag_1_debug.log'.
Please attach this file to your report.
INFO: storing files of previous run 
gzipping output file: unweighted_events.lhe
INFO: Done 


I do have "unweighted_events.lhe_0.lhe" in that path, but not the .gz file. In "run_01_tag_1_debug.log", I find the following message: 


generate_events run_01
Traceback (most recent call last):
  File "/home/xutao/HEP/MG5_aMC_v2_5_5/madgraph/interface/extended_cmd.py", line 1430, in onecmd
    return self.onecmd_orig(line, **opt)
  File "/home/xutao/HEP/MG5_aMC_v2_5_5/madgraph/interface/extended_cmd.py", line 1384, in onecmd_orig
    return func(arg, **opt)
  File "/home/xutao/HEP/MG5_aMC_v2_5_5/madgraph/interface/madevent_interface.py", line 2130, in do_generate_events
    self.exec_cmd('shower --no_default', postcmd=False, printcmd=False)
  File "/home/xutao/HEP/MG5_aMC_v2_5_5/madgraph/interface/extended_cmd.py", line 1457, in exec_cmd
    stop = Cmd.onecmd_orig(current_interface, line, **opt)
  File "/home/xutao/HEP/MG5_aMC_v2_5_5/madgraph/interface/extended_cmd.py", line 1384, in onecmd_orig
    return func(arg, **opt)
  File "/home/xutao/HEP/MG5_aMC_v2_5_5/madgraph/interface/madevent_interface.py", line 3441, in do_shower
    postcmd=False, printcmd=False)
  File "/home/xutao/HEP/MG5_aMC_v2_5_5/madgraph/interface/extended_cmd.py", line 1457, in exec_cmd
    stop = Cmd.onecmd_orig(current_interface, line, **opt)
  File "/home/xutao/HEP/MG5_aMC_v2_5_5/madgraph/interface/extended_cmd.py", line 1384, in onecmd_orig
    return func(arg, **opt)
  File "/home/xutao/HEP/MG5_aMC_v2_5_5/madgraph/interface/madevent_interface.py", line 4058, in do_pythia8
    pjoin(parallelization_dir,split_files[-1]))
  File "/usr/lib64/python2.6/shutil.py", line 260, in move
    copy2(src, real_dst)
  File "/usr/lib64/python2.6/shutil.py", line 95, in copy2
    copyfile(src, dst)
  File "/usr/lib64/python2.6/shutil.py", line 50, in copyfile
    with open(src, 'rb') as fsrc:
IOError: [Errno 2] No such file or directory: '/home/xutao/HEP/MG5_aMC_v2_5_5/bin/PROC_sm_1/Events/run_01/unweighted_events.lhe_0.lhe.gz'
Related File: /home/xutao/HEP/MG5_aMC_v2_5_5/bin/PROC_sm_1/Events/run_01/unweighted_events.lhe_0.lhe.gz


I'm not sure if I used the patch right. Can you help me with this?

Many thanks,
Tao Xu