I propose a way we can make progress ... Let's start populating a matrix (excel spreadsheet) with a column for each MPI implementation, and rows for the various MPI datatypes, constants, etc. where the internal implementations varys. I'll kick it off for OpenMPI and send out. The last column of the matrix can be "ABI" where we propose a common approach across the implementations. A couple of driving principles: 1. the ABI solution shouldn't negatively impact quality of implementation 2. minimize platform specific solutions I'd like to see if we can produce a single ABI that spans platforms. comments? Jeff