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Subject: Re: [OMPI devel] running OpenMPI examples on two hosts
From: Ralph Castain (rhc_at_[hidden])
Date: 2011-10-12 14:55:05


I believe the btl must include self - can't just be openib. So you need -mca btl self,openib, otherwise the proc cannot talk to itself.

On Oct 12, 2011, at 12:46 PM, Bhargava Ramu Kavati wrote:

> Hi,
> I am using OpenMPI version 1.4.3 on CentOS5.4 machines (connected back to back using Infiniband HW)
> I am trying to run example apps in OpenMPI using the below command.
>
> "mpirun --prefix /usr/local/ -np 2 --mca btl openib --mca btl_openib_cpc_include rdmacm -hostfile tmp_host_file ring_c"
>
> Here tmp_host_file contains IP addresses of two hosts. After running this command, I see the error as
>
> "At least one pair of MPI processes are unable to reach each other for
> MPI communications. This means that no Open MPI device has indicated
> that it can be used to communicate between these processes. This is
> an error; Open MPI requires that all MPI processes be able to reach
> each other."
> This clearly indicates that there is an option missing the command due to which MPI processes are not able to reach each other. Can you please let me know
> 1) how do we resolve this
> 2) IP is the only way for MPI processes to reach each other (i.e. it'll go via IPoIB in infiniband case) ?
>
> Thanks & Regards,
> Ramu
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