Add a DATA_GEN flag telling if it is necessary to generate data or not
Add a DATA_GEN flag telling if it is necessary to generate data or not

As data generation is kind of problematic on the cluster,
this flag allows data generation on a computer X,
and then the cluster take over for the result computation.

chagaz/sfan,chagaz/sfan,chagaz/sfan,chagaz/sfan,chagaz/sfan