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Subject: Re: [OMPI devel] [patch] MPI_IN_PLACE for MPI_ALLTOALL(V|W)
From: George Bosilca (bosilca_at_[hidden])
Date: 2013-09-17 03:39:02


Takahiro,

Good catches. It's absolutely amazing that some of these errors lasted for so long before being discovered (especially the extent issue in the MPI_ALLTOALL). Please feel free to apply your patch and add the correct copyright at the beginning of all altered files.

  Thanks,
    George.

On Sep 17, 2013, at 07:36 , "Kawashima, Takahiro" <t-kawashima_at_[hidden]> wrote:

> Hi,
>
> My colleague tested MPI_IN_PLACE for MPI_ALLTOALL, MPI_ALLTOALLV,
> and MPI_ALLTOALLW, which was implemented two months ago in Open MPI
> trunk. And he found three bugs and created a patch.
>
> Found bugs are:
>
> (A) Missing MPI_IN_PLACE support in self COLL component
>
> The attached alltoall-self-inplace.c fails with MPI_ERR_ARG.
> self COLL component also must support MPI_IN_PLACE.
>
> (B) Incorrect rcount[] index
>
> A trivial bug in the following code.
>
> for (i = 0, max_size = 0 ; i < size ; ++i) {
> size_t size = ext * rcounts[rank]; // should be rcounts[i]
>
> max_size = size > max_size ? size : max_size;
> }
>
> This causes SEGV or something.
>
> (C) For MPI_ALLTOALLV, the unit of displacements is extent, not byte
>
> Though the unit of displacements is byte for MPI_ALLTOALLW,
> the unit of displacements is extent for MPI_ALLTOALLV.
>
> MPI-2.2 (page 171) says:
>
> The outcome is as if each process sent a message to every
> other process with,
> MPI_Send(sendbuf + sdispls[i] · extent(sendtype),
> sendcounts[i], sendtype, i, ...),
> and received a message from every other process with a call to
> MPI_Recv(recvbuf + rdispls[i] · extent(recvtype),
> recvcounts[i], recvtype, i, ...).
>
> I attached his patch (alltoall-inplace.patch) to fix these three bugs.
>
> Takahiro Kawashima,
> MPI development team,
> Fujitsu
> <alltoall-inplace.patch><alltoall-self-inplace.c>_______________________________________________
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