After having modified the file madgraph/iolibs/export_v4.py, this is what I got: INFO: Use Fortran compiler gfortran INFO: Use c++ compiler g++ COMPILER g++ Command "output Zjj_new" interrupted with error: OSError : [Errno 12] Cannot allocate memory Please report this bug on https://bugs.launchpad.net/madgraph5 More information is found in 'MG5_debug'. Please attach this file to your report. Cheers, Francesco On 24 Jan 2015, at 17:27, Francesco Giuli <