I believe that this is something Brad at IBM worked on, wasn't it? I
*think* you may just need the development trunk (i.e., upcoming v1.3),
but I won't swear to that.
Regardless, you need to have OMPI compiled for heterogeneous support
because control headers still need to be adjusted for endian-ness,
etc. (even if you're only sending MPI_BYTE).
On Aug 25, 2008, at 1:57 PM, Mi Yan wrote:
Brian,
I'm using OpenMPI 1.2.6 (r17946). Could you plese check which
version works ? Thanks a lot,
Mi
<graycol.gif>"Brian W. Barrett" <brbar...@open-mpi.org>
"Brian W. Barrett" <brbar...@open-mpi.org>
Sent by: users-boun...@open-mpi.org
08/25/2008 01:44 PM
Please respond to
Open MPI Users <us...@open-mpi.org>
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To
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Open MPI Users <us...@open-mpi.org>
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cc
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Greg Rodgers/Poughkeepsie/IBM@IBMUS, Brad Benton/Austin/IBM@IBMUS
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Subject
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Re: [OMPI users] RDMA over IB between heterogenous processors with
different endianness
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On Mon, 25 Aug 2008, Mi Yan wrote:
> Does OpenMPI always use SEND/RECV protocol between heterogeneous
> processors with different endianness?
>
> I tried btl_openib_flags to be 2 , 4 and 6 respectively to allowe
RDMA,
> but the bandwidth between the two heterogeneous nodes is slow,
same as
> the bandwidth when btl_openib_flags to be 1. Seems to me SEND/RECV
is
> always used no matter btl_openib_flags is. Can I force OpenMPI to
use
> RDMA between x86 and PPC? I only transfer MPI_BYTE, so we do not
need the
> support for endianness.
Which version of Open MPI are you using? In recent versions (I don't
remember exactly when the change occured, unfortuantely), the decision
between send/recv and rdma was moved from being solely based on the
architecture of the remote process to being based on the
architecture and
datatype. It's possible this has been broken again, but there
defintiely
was some window (possibly only on the development trunk) when that
worked
correctly.
Brian
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Cisco Systems
