[mvapich-discuss] MPI-2 over ibverbs/rdma

[Jonathan Perkins]

On Wed, Nov 25, 2009 at 02:04:13PM +0530, Vivek Satpute wrote:
> Hi,
> 
> First of all thanks for the instant reply.
> 
> I am bit confused with IPoIB and MPI-2. Please find inline reply/questions .
> 
> On Wed, Nov 25, 2009 at 1:38 PM, Dhabaleswar Panda wrote:
> > You can use the OpenFabrics-Gen2/IB interface of MVAPICH2 to run it
> > directly over ibverbs.
>
> If  I configured above then for executing MPI application from node1
> to node2, node3 and node4 (e.g mpirun_rsh -np 4 n0 n1 n2 n3 ./cpi), I
> will have to mention a IB interfaces of each n0, n1, n3, n4. So
> ultimately MPI will use IPoIB module. Am i right ?

You shouldn't need to specify any additional information.  The
mpirun_rsh command only needs to know which nodes you're trying to
launch mpi program on.  It appears that you're basing your questions on
some additional assumptions.  Are you asking this question based on some
problem that you're run into?

MPI is an API that you write your software against.  You don't need to
worry about what the underlying transport is (thus it doesn't matter if
IPoIB is used or not).  When you build mvapich2 with its default options
it will know to use IB communications and thus will try to use the first
working IB interface on each of the nodes that you run the MPI
application on.  The only reason you should need to specify the
interface you want to use is when you have a special configuration where
the default behaviour is not desirable.

> 
> Please refer to MVAPICH2 1.4 user guide (available from the following
> > URL). This indicates how to build, configure and run MVAPICH2 on Gen2
> > interface.
> >
> > http://mvapich.cse.ohio-state.edu/support/user_guide_mvapich2-1.4.html
> >
> > Hope this helps.
> >
> > DK
> >

-- 
Jonathan Perkins
http://www.cse.ohio-state.edu/~perkinjo
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