I've installed OpenMPI on my Ubuntu 11.04 machine.
My understanding is that I type mpirun and magic happens.
What I don't understand is how to configure mpirun to make this magic happen only on my machine's two cores.
How do you configure OpenMPI to run on a single machine using multiple of its cores?
There's no configuration needed, just pass the "-n 2" option to mpirun and it will start two processes. The mpirun documentation provides further information.