[OMPI users] Best MPI implementation

[Tony Power]

Hi!
I am going to start my approach to parallel programming (on C or C++)
and I would like to know what should I learn/use, LAM MPI, OpenMPI, or
any other MPI implementation.
Can anyone advise me please?
I believe OpenMPI would be best, but I can't find any tutorial on OpenMPI.
Thank you very much ;)