so configuring the MPI flags I have realized that in the /usr/include directory there are two folders with the same files. So two related questions:
All the best and thanks in advance,
This can depend on your installation, but this is a common way for providing several parallel MPI installation.
I have both MPICH2 and OpenMPI installed, and this folders in /usr/include:
lrwxrwxrwx 1 root root 21 Apr 1 17:03 mpi -> /etc/alternatives/mpi/
drwxr-xr-x 3 root root 4096 Apr 1 17:03 mpich/
lrwxrwxrwx 1 root root 22 Nov 30 01:21 openmpi -> ../lib/openmpi/include/
And mpi folder is a folder which should be used as #include to make use of alternatives mechanism (I recommend starting from this and this, it's available on other than Debian based distros).
If you run update-alternatives --config mpi you can change the default MPI distribution.
Example, /etc/alternatives/mpi before and after update-alternatives:
# before, pointing to MPICH2
lrwxrwxrwx 1 root root 18 Apr 1 17:14 /etc/alternatives/mpi -> /usr/include/mpich/
# and after, pointing to OpenMPI
lrwxrwxrwx 1 root root 24 Apr 1 17:07 /etc/alternatives/mpi -> /usr/lib/openmpi/include/
Summarizing:
/usr/include/mpi/ to make your code as much portable as possible.update-alternatives to change the desired MPI distro.alternatives to provide easy way of multiple version (and distributions) of software.
