SYNOPSYS
This class is mainly used to initialize the MPI library: it should be called juste after the main(argc,argv) declaration as in:
#include "rheolef.h"
using namespace rheolef;
int main(int argc, char**argv) {
environment rheolef (argc, argv);
...
}
An optional third argument of the environment constructor
allows to set the MPI thread feature. By default, its value
is MPI_THREAD_SINGLE, as defined in mpi.h.
Other possible values are related to MPI multi-threaded, see
the MPI documentation for more details.

