Q) Why doesn't the mpirun option do what the help pages say it shoud do?
A) mpirun options must be specified before the name of the executable. Any options specified after the executable will be passed as arguments to the executable and not parsed as mpirun options. For example: mpirun -np 5 myapp.exe -machinefile filename will not use the machine file specified by filename because mpirun considers this an argument to the application.