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Subject: Re: [OMPI users] MPI_Isend delay
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2011-07-14 19:48:21

On Jul 14, 2011, at 5:50 PM, dave fournier wrote:

> I have a master-slave setup. I have noticed that when I send a message from the master to the slave
> processes using MPI_Isend it never gets sent until I encounter an MPI_recv in the master process.

How are you testing that?

> As a result rhe slave processes are wasting time waiting for the message.

Er... I'm not sure I can parse this. You said that the message doesn't go until the slave calls MPI_Recv. So I don't quite understand how the slave is wasting time...?

> If I use MPI_Send
> instead of MPI_Isend all works fine. I don't understand what is going on here.

Define "fine" -- can you be a bit more precise about the exact behavior that you want to see, and the behavior that you are seeing, and the difference that MPI_SEND makes vs. MPI_ISEND?

Jeff Squyres
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