At the end of the call, Jeff asked about a simple example that illustrates building a tool with QMPI that works with multiple MPI implementations. I've attached a tarball that illustrates what I was picturing. This example builds a pair of libraries, libfakeopenmpi.so and libfakempich.so, which each export "mpisend" functions with different signatures as well as a pair of fake apps, app_openmpi and app_mpich, that use each library. It also builds a single libtool.so, which contains wrapper functions for each mpisend and dynamically chooses which one is used. Note that the tool library still has files built against each MPI implementation, but produces a single library that works with either implementation. On the phone I speculated that you'd need the callback registration functions to be ABI compatible across all MPI implementations, but this didn't turn up being necessary. You can get away with only the MPI identification function having a standard ABI. In this example I called the function get_mpi_implementation(). It also turned up being very convenient if the MPI header exported the return value of get_mpi_implementation() though a #define (which I called MPI_IMPL). This allowed for an easy runtime test of whether the a tool implementation was compiled for the running MPI. Also, On the phone I speculated that getting per-compiler tools would be difficult. You actually could solve part of the problem by including a compiler name and version in the MPI_IMPL #define--most compilers have preprocessor macros that exports that info. Though this still wouldn't solve any tool incompatibilities with runtime libraries like libstdc++.so. -Matt