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

[Nathalie Furmento <nathalie.furmento@labri.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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