Hi all, if I understood the discussion about MPI_Session_init and PMPI right, I don't think there exists an issue. By ld-preloading the PMPI tool, the tool can also intercept a call to MPI_Session_init, which might come from a library constructor before main. Even a function called from the library constructor of a static library can be intercepted by a ld-preloaded tool. For libraries, which are explicitly loaded by the MPI runtime during initialization, this would also work. For others, it depends on the ordering of calling the library constructor (might work by chance :). This was one of my main motivation of having such an environmental variable. Best Joachim -- Dipl.-Inf. Joachim Protze IT Center Group: High Performance Computing Division: Computational Science and Engineering RWTH Aachen University Seffenter Weg 23 D 52074 Aachen (Germany) Tel: +49 241 80- 24765 Fax: +49 241 80-624765 [email protected] www.itc.rwth-aachen.de