Displayed are a few quick tests, to assess the gain of P&K MPI. One can see that the gain isn't constant. This is because the relation between CPU usage and I/O changes with lower QS to more impact of I/O. Its still one computer only. The decrease of gain with 4 processes on a 4-core computer can be explained with the impact by the active operating system.
300x300= 300 by 300 cells; c= Cores