I haven't investigated implementations in any depth recently, but recent quick looks confirms that quite a few MPI features are NOT available in all of the major ones. I know that is true for heterogeneous systems, and the more extreme threading options, but there are quite a few other areas where I should be flabberghasted if it were not. And, of course, at least some of the almost-unused features don't actually work quite right, but don't get fixed because nobody gives a damn ....

MPICH2 supports essentially everything except heterogeneous (in the 32/64-bit sense, for example; GPUs are a different issue) as far as I know. I don't know anyone running such a system anyways, since all modern Linux systems are 64-bit. Mixing endianness is even more rare; I don't know anyone that cares about this scenario. Microsoft MPI, MVAPICH2, Cray MPI, Intel MPI and IBM Blue Gene MPI are all based upon MPICH2 so they should have similar feature support. Cray and IBM Blue Gene do not support dynamic processes yet. Blue Gene will never support them in a nontrivial way, although I know how to make the implementation standard compliant to the letter of the standard (it's not worth doing because no one cares). Can you list some of the "quite a few" features that are not available in MPICH2 and OpenMPI, which I contend are the "major ones"? It's somewhat frustrating that you write to this list with statements about all the things about MPI that don't work but never actually follow through and enumerate them in such a way that someone like me could determine the veracity of your statements. In the future, can you please provide such lists in the first message rather than going around and around without ever posting them. You still haven't posted a specific instance of C99-MPI incompatibility that one can verify... Jeff -- Jeff Hammond Argonne Leadership Computing Facility University of Chicago Computation Institute [email protected] / (630) 252-5381 http://www.linkedin.com/in/jeffhammond https://wiki.alcf.anl.gov/parts/index.php/User:Jhammond