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Subject: Re: [OMPI users] nonblock alternative to MPI_Win_complete
From: Toon Knapen (toon.knapen_at_[hidden])
Date: 2011-02-24 07:07:07


In that case, I have a small question concerning design:

Suppose task-based parallellism where one node (master) distributes
work/tasks to 2 other nodes (slaves) by means of an MPI_Put. The master
allocates 2 buffers locally in which it will store all necessary data that
is needed by the slave to perform the task. So I do an MPI_Put on each of my
2 buffers to send each buffer to a specific slave. Now I need to know when I
can reuse one of my buffers to already store the next task (that I will
MPI_Put later on). The only way to know this is call MPI_Complete. But since
this is blocking and if this buffer is not ready to be reused yet, I
can neither verify if the other buffer is already available to me again (in
the same thread).

I would very much appreciate input on how to solve such issue !

thanks in advance,

toon

On Tue, Feb 22, 2011 at 7:21 PM, Barrett, Brian W <bwbarre_at_[hidden]>wrote:

> On Feb 18, 2011, at 8:59 AM, Toon Knapen wrote:
>
> > (Probably this issue has been discussed at length before but
> unfortunately I did not find any threads (on this site or anywhere else) on
> this topic, if you are able to provide me with links to earlier discussions
> on this topic, please do not hesitate)
> >
> > Is there an alternative to MPI_Win_complete that does not 'enforce
> completion of preceding RMS calls at the origin' (as said on pag 353 of the
> mpi-2.2 standard) ?
> >
> > I would like to know if I can reuse the buffer I gave to MPI_Put but
> without blocking on it, if the MPI lib is still using it, I want to be able
> to continue (and use another buffer).
>
>
> There is not. MPI_Win_complete is the only way to finish a MPI_Win_start
> epoch, and is always blocking until local completion of all messages started
> during the epoch.
>
> Brian
>
> --
> Brian W. Barrett
> Dept. 1423: Scalable System Software
> Sandia National Laboratories
>
>
>
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