Ok, i am quite lost. Also googling the error you get is not of much help… Try this: Open the file madgraph/iolibs/export_v4.py and comment these p = misc.Popen([compiler, '--version'], stdout=subprocess.PIPE, stderr=subprocess.PIPE) output, error = p.communicate() is_clang = 'LLVM' in output and add is_clang = False in place of the last line. What happens if you now try to re-export your process? Let me know, Marco On 27 Jan 2015, at 08:45, Francesco Giuli