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Re: [Starpu-devel] MPI datatypes for user-defined interfaces


Chronologique Discussions 
  • From: Nathalie Furmento <nathalie.furmento@labri.fr>
  • To: Marc Sergent <marc.sergent@inria.fr>, starpu-devel@lists.gforge.inria.fr
  • Subject: Re: [Starpu-devel] MPI datatypes for user-defined interfaces
  • Date: Thu, 04 Jun 2015 16:33:59 +0200
  • List-archive: <http://lists.gforge.inria.fr/pipermail/starpu-devel/>
  • List-id: "Developers list. For discussion of new features, code changes, etc." <starpu-devel.lists.gforge.inria.fr>

Hello,

The functionality has been added to the trunk and to the branch 1.2.

An example using it is available in mpi/examples/user_datatype

Cheers,

Nathalie

On 06/05/2015 13:45, Marc Sergent wrote:
Hello,

I am working on a user interface for StarPU for compressible matrices, which is in fact an extension of the matrix interface of StarPU (i.e the code of my user interface which handles non-compressed matrices is exactly the same as the code of the matrix interface of StarPU). I want to use it in Chameleon to perform distributed computation, so I provided pack/unpack functions to the interface.

I tried to validate the performance of my user interface on a specific test case which uses non-compressed matrices (dpotrf, N=65536, NB=512, 4 computing nodes with 8 CPUs + 2GPUs on each node) by comparing it to the matrix interface of StarPU currently used by Chameleon, and I confirmed that the performance I obtained with my user interface is significantly worse than the one I obtained with the matrix interface of StarPU. I also confirmed that the performance obtained on a single node test case (N=32768, NB=512, 8 CPUs + 2 GPUs) is similar.

After checking the code, I realized that the matrix interface has predefined functions to use an optimized MPI dataype for MPI communications, while the data decribed with user-defined interfaces are always communicated using the MPI_BYTE datatype combined with pack/unpack function calls.

It seems that it is not possible to give a user-defined function for defining an MPI datatype for a data described by a user-defined interface to StarPU-MPI. Is that a feature you would want to implement in StarPU-MPI ?

Thanks in advance,
Regards,

Marc Sergent

---
Marc Sergent
Ph.D Student at Inria Bordeaux Sud-Ouest
STORM Team
Phone: (+33|0) 5 24 57 40 71

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  • Re: [Starpu-devel] MPI datatypes for user-defined interfaces, Nathalie Furmento, 04/06/2015

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