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Subject: Re: [OMPI users] Regarding hyperthreding
From: seshendra seshu (seshu199_at_[hidden])
Date: 2012-08-14 07:55:31


Hi Tom,

Thank you.

I haven't still changed my code to run when threading is needed (presently
working).
I have doubt that when i calculate the MPI ranks using the MPI command it
gives only the nodes which have given in a host file.
But how can i calculate the MPI ranks as you have told i.e N=H( number
of CPUs showing on a node ) x M ( number of nodes in a cluster).

And I would like test like this if have 2 nodes and where I can use up to
50 cores. I would like to scale like 2,4,8,16,32,45 cores and at the same
time if use 8 cores then I would like to take the readings as node1- 3cores
and node2-5 cores. So in order to do that should I need mention anything in
the host file as I have mentioned the No.of nodes.

And can provide me any tutorials which explains with an example programs.

Thanking you,

On Mon, Aug 13, 2012 at 6:59 PM, Elken, Tom <tom.elken_at_[hidden]> wrote:

> Hi Seshendra,****
>
> ** **
>
> If you have implemented hyperthreading by Enabling it in the BIOS, then
> when you look at****
>
> cat /proc/cpuinfo output, you will see 2x the # of CPUs than the number of
> cores on your system. ****
>
> If that number of CPUs showing on a node = H, and the number of nodes in
> your cluster with this same configuration is M, ****
>
> Then you can run your program on up to N = H x M MPI ranks,****
>
> and your Open MPI mpirun command can use the****
>
> ‘-np N –npernode H’ options to indicate this.****
>
> ** **
>
> Note that with some applications, you may see very little benefit to
> hyperthreading. In any case, you should also run on “-np N/2” ranks and
> add the “-npernode H/2” setting to not use more ranks per node than you
> have cores per node, and compare performance with N ranks (with H per node).
> ****
>
> ** **
>
> -Tom****
>
> ** **
>
> ****
>
> ** **
>
> *From:* users-bounces_at_[hidden] [mailto:users-bounces_at_[hidden]] *On
> Behalf Of *seshendra seshu
> *Sent:* Monday, August 13, 2012 9:27 AM
> *To:* Open MPI Users
> *Subject:* [OMPI users] Regarding hyperthreding****
>
> ** **
>
> Hi,****
>
> I have written an code mpi and an iam trying to implement hyperthreading
> environment. So could any one tell me how to implement and run the
> program in open mpi.****
>
> ** **
>
> Kindly help me.****
>
> ** **
>
> Thanking you,****
>
> ** **
>
> ** **
>
>
> --
> WITH REGARDS
> M.L.N.Seshendra****
>
> _______________________________________________
> users mailing list
> users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/users
>

-- 
 WITH REGARDS
M.L.N.Seshendra