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Anders_S_1
Beginner
124 Views

Intel MPI gives wrong number of physical cores on core i7 Q820?

Hi,

I have begun learning MPI on my Dell 4500 with a Core i7 Q820 processor (4 physical and 8 logical cores).

When I run a simple program in Fortran to get the rank and size, i get 0 and 1 instead of 0 and 3 (see attached code).

What is wrong?

Best regards

Anders S

0 Kudos
5 Replies
Artem_R_Intel1
Employee
124 Views

Hi Anders,
As far as I understand you run the MPI program without MPI launcher (like mpirun), correct?
$ ./mpitest
rank,size=   0   1
It's similar to:
$ mpirun -n 1 ./mpitest
rank,size=   0   1

Why do you expect '0 and 3'?

You can try to vary the number of MPI processes with '-n <procs>' option:
$ mpirun -n 4 ./mpitest
rank,size=   1   4
rank,size=   2   4
rank,size=   3   4
rank,size=   0   4

I'd recommend to look at the Getting Started with Intel® MPI Library document.

Artem_R_Intel1
Employee
124 Views

Hi Anders,
As far as I understand you run the MPI program without MPI launcher (like mpirun), correct?
$ ./mpitest
rank,size=   0   1
It's similar to:
$ mpirun -n 1 ./mpitest
rank,size=   0   1

Why do you expect '0 and 3'?

You can try to vary the number of MPI processes with '-n <procs>' option:
$ mpirun -n 4 ./mpitest
rank,size=   1   4
rank,size=   2   4
rank,size=   3   4
rank,size=   0   4

I'd recommend to look at the Getting Started with Intel® MPI Library document.

Anders_S_1
Beginner
124 Views

Artem R. (Intel) wrote:

Hi Anders,
As far as I understand you run the MPI program without MPI launcher (like mpirun), correct?
$ ./mpitest
rank,size=   0   1
It's similar to:
$ mpirun -n 1 ./mpitest
rank,size=   0   1

Why do you expect '0 and 3'?

You can try to vary the number of MPI processes with '-n <procs>' option:
$ mpirun -n 4 ./mpitest
rank,size=   1   4
rank,size=   2   4
rank,size=   3   4
rank,size=   0   4

I'd recommend to look at the Getting Started with Intel® MPI Library document.

Hi Artem,

Thank you for your answer!

My Dell M4500 broke down and I have continued with a Dell M4800 with a Core i7 4910MQ processor.

Furthermore, I have installed the Parallell Studio Cluster software.

When I run the simple test code (attached) with no use of MPI compile, link and run was OK.

When I added just the line

INCLUDE 'mpif.h'

compile was OK but link gave a number of warnings and errors (attached link message printout)

What have I missed?

Best regards

Anders S

James_T_Intel
Moderator
124 Views

Did you add impi.lib to your library input?

Anders_S_1
Beginner
124 Views

Hi James,

Thanks for your answers. As I just after your first reply installed the Cluster studio I found it better to start a new, hopefully better defined case called "Trying to make MPI work in a QuickWin application". I think your last comment may be relevant in the new case.

Best regards

Anders S

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