Hi list, It appears there is a problem with the OpenMPI I/O library on CentOS 6.2 & 6.3 (package openmpi-1.5.4-1.el6.x86_64). When I compile the attached program it ends up in the error path since MPI_File_open returns 16. The corresponding (unhelpful) message is: MPI_ERR_OTHER: known error not in list I couldn't find any pointers on the net and the same program works with OpenMPI 1.4.5 on a debian system. Any help would be greatly appreciated. Cheers, Cihan