FYI I ran a 10 way Monte-carlo simulation (Option pricing) on a Sunfire 1280. I also compared it to the one node case. If you are interested I used mpich-1.2.6 with pyMPI 2.1 b4 & Python-2.4 on solaris. Used following command lines:
time mpirun -np 10 pyMPI  =  148.73u 0.73s 2:31.52 98.6%
time mpirun -np  1 pyMPI = 15.41u 1.25s 0:23.02 72.3%
When I looked at the times, the actual CPU speedup looks like an impressive 9.65x (148.73 / 15.41) over the single cpu run. On the other hand the elapsed time 2:31.52 / 0:23.02 is only a 6.5 speedup. I would probably have to use LAM to remove the startup lag (If that's the difference), but I only have MPICH installed at the moment.
Anyway, it's a lot faster. If anyone is interested in seeing the python code let me know.
Julian Cook