Hi, I have a Fortran application that uses MPI_Comm_Spawn. When I run with it compiled using gfortran/gcc (and mpich compiled with gfortran/gcc), it just hangs forever. When I run with it compiled using ifort/icc (and mpich compiled with ifort/icc), it runs correctly. When I run it in GDB with the GNU compiler suite and interrupt it once it's stuck, it tells me: Program received signal SIGINT, Interrupt. 0x00007ffff7800fc9 in pmpi_comm_spawn__ () from /opt/mpi/mpich/gnu/system/lib64/libmpich.so.8 and this is with both mpich 1.4 and 1.5. Does anybody have any suggestions for what could be going on? It really just sits there, doing absolutely nothing, forever. No timeouts, no errors or warnings. I'm not ruling out a bug in my codes, but I don't even know where to begin. Thanks, Tim