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4f0drlp7eyj3
Beginner
89 Views

Mapping ranks consecutively on nodes

Hi,

   Running Intel MPI 4.1.3

   Contrary to the user guide, which states for the default round-robin mapping,

To change this default behavior, set the number of processes per host by using the -perhost option, and set the total number of processes by using the -n option. See Local Options for details. The first <# of processes> indicated by the -perhost option is executed on the first host; the next <# of processes> is executed on the next host, and so on.

, when I try to run on 2 nodes and I_MPI_DEBUG=4, I see

[cchang@n0290]$ mpirun -n 4 -perhost 2 ./hello_MPIMP_multinode
[0] MPI startup(): Rank    Pid      Node name  Pin cpu
[0] MPI startup(): 0       54622    n0290      {0,1,2,3,4,5,6,7,8,9,10,11}
[0] MPI startup(): 1       53310    n0289      {0,1,2,3,4,5,6,7,8,9,10,11}
[0] MPI startup(): 2       54623    n0290      {12,13,14,15,16,17,18,19,20,21,22,23}
[0] MPI startup(): 3       53311    n0289      {12,13,14,15,16,17,18,19,20,21,22,23}
Hello world: rank 0 of 4, thread 0 of 1 on n0290
Hello world: rank 2 of 4, thread 0 of 1 on n0290
Hello world: rank 1 of 4, thread 0 of 1 on n0289
Hello world: rank 3 of 4, thread 0 of 1 on n0289

Both the I_MPI_DEBUG and the actual test program output confirm that round-robin scheduling is being done.

I can't seem to change this with any combination of -perhost #, or -grr #. I can create a machinefile that specifies the number of ranks per node and it will map as desired, but I'm guessing I should be able to do this simply from the mpirun command. How is this done?

Thanks; Chris

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4 Replies
TimP
Black Belt
89 Views

Back then there were some flip flops version to version on how perhost was working, so I'm not entirely surprised at your finding.  What does surprise is your desire to rely on a version which was retired before me.

Artem_R_Intel1
Employee
89 Views

Hi Chris,

As it's mentioned in the Intel® MPI Library for Linux* OS Reference Manual:
The -machinefile, -ppn, -rr, and -perhost options are intended for process distribution. If used simultaneously, -machinefile takes precedence.

You can try '-f ' or '-hostfile' mpirun options (instead of '-machinefile') which are able to work in conjunction with '-ppn'/'-perhost' options.

4f0drlp7eyj3
Beginner
89 Views

Tim--

   Not sure I understand. Intel MPI 4.1 update 3 build 049 was released Mar 2014. We've put off upgrading to 5.0 because we're leery of putting .0 versions of anything into production.
 

4f0drlp7eyj3
Beginner
89 Views

Artem--

   Thanks. I was hoping there was a short and sweet way (not that generating a machinefile is especially onerous) of packing consecutive ranks to consecutive node ids. The machinefile works fine, just wondered if I was misinterpreting the documentation somehow, or if there were an environment variable that we'd missed setting to get the documented behavior.

Cheers,

Chris

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