mpirun -np N, what if N is larger than my core number?

Posted by Daniel on Ask Ubuntu See other posts from Ask Ubuntu or by Daniel
Published on 2012-05-30T21:42:26Z Indexed on 2012/05/30 22:51 UTC
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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.

© Ask Ubuntu or respective owner

mpirun -np N, what if N is larger than my core number?

Posted by Daniel on Super User See other posts from Super User or by Daniel
Published on 2012-05-30T21:52:51Z Indexed on 2012/05/30 22:43 UTC
Read the original article Hit count: 467

Filed under:
|
|

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.

© Super User or respective owner

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