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Subject: Re: [OMPI users] Multi-rail support
From: Rolf Vandevaart (Rolf.Vandevaart_at_[hidden])
Date: 2010-03-25 08:37:35

They will automatically be used by the library. There is nothing
special that you need to do. Unfortunately, there is no simple way to
tell if they are being used. I would suggest that you specifically call
them out in different calls to mpirun to make sure they are both
working. If they both work individually, then you can assume they are
both being used. You will only see better performance with larger
messages. Something like this:

mpirun -mca btl_openib_if_include mlx4_0 a.out
mpirun -mca btl_openib_if_include mlx4_1 a.out

You need to find out your device names from the command ibv_devinfo or


On 03/25/10 05:53, Dmitry Kuzmin wrote:
> Hi there,
> We have a cluster with 2 HCAs installed on each node (Mellanox ConnectX
> IB QDR cards). It's not clear from the documentation how we could use
> both of them for MPI communications.
> What should we do to enable 2 cards and how we can check that both are
> using?
> Thanks in advance!
> Dmitry
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