Re: [Boost-users] mpi isend to group

Subject: Re: [Boost-users] mpi isend to group
From: Andreas Schäfer (gentryx_at_[hidden])
Date: 2012-12-30 17:22:13

On 23:12 Sun 30 Dec     , Philipp Kraus wrote:
> Sorry I have forgot a "main information": This calls are a preexecution of
> the algorithm. The main algorithm is cycled and uses a MPI blocking
> communication, so only the preexecution must be a little bit weak. 

Sorry, I don't quite get it. Could you elaborate on this? What is in
this context the "preexecution", what is the main algorithm, and what
do you mean by "must be a little bit weak"?

> Thanks for the code, but this code is based on OpenMPI. My program must
> be also work wirth MPI CH2 (MPI implemention on Windows based systems),
> so I would like to create a boost-only solution. 

The code uses the MPI standard interface, it contains nothing specific
to Open MPI (BTW: it's not called "OpenMPI", but that's just
nitpicking). It thus works with MPICH2, too -- no matter if the OS is
Linux or Windows.

> I do it at the moment with:
> 
> while (thread_is_running) {
> 
>             if (!l_mpicom.rank())
>                     for(std::size_t i=1; i < l_mpicom.size(); ++i)
>                         l_mpicom.isend(i, 666, l_task.getID());
>             else
>                 if (boost::optional<mpi::status> l_status = l_mpicom.iprobe(0, 666))
>                 {
>                     std::size_t l_taskid = 0;
>                     l_mpicom.recv(  l_status->source(), l_status->tag(), l_taskid );
>                 }
> }

You could rebuild the binary tree communication scheme I've
illustrated using Boost MPI (I'm too lazy). I'm pretty sure calling
isend() without ever waiting for completion is illegal according to
the MPI standard and will result in a memory leak (plus the code won't
scale thanks to the for loop).

Cheers
-Andreas

-- 
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Andreas Schäfer
HPC and Grid Computing
Chair of Computer Science 3
Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
[phone]
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http://www.libgeodecomp.org
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