Say I have a 4-core workstation, what would linux (Ubuntu) do if I execute
mpirun -np 9 XXX
Q1. Will 9 run immediately together, or they will run 4 after 4?
Q2. I suppose that using 9 is not good, because the remainder 1, it 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?
Q3. 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.
Q4. Who decides all of these effciency optimization, Ubuntu, or linux, or motherboard or cpu?
Your enlightenment would be really appreciated.