Say I have a 4-core workstation, what would Linux (Ubuntu) do if I execute
mpirun -np 9 XXX
Will 9 run immediately together, or they will run 4 after 4?
I suppose that using 9 is not good, because the remainder 1 will make the computer confused, (I don't know is it going to be confused at all, or the "head" of the computer will decide which core among the 4 cores will be used?) Or it will be randomly picked. Who decide which one core to call?
If I feel my cpu is not bad and my ram is okay and large enough, and my case is not very big. Is it a good idea in order to fully use my cpu and ram, that I do
mpirun -np 8 XXX, or even
mpirun -np 12 XXX.