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Subject: Re: [OMPI users] How to check if Send was made or not before performing a recv
From: Eugene Loh (eugene.loh_at_[hidden])
Date: 2010-12-11 10:28:53

Alaukik Aggarwal wrote:

>I am using Open MPI 1.4.3.
>I have to perform a receive operation from processes that are sending
>data. It might happen that some of the processes don't send data
>(might have completed in-fact).
>So, how do I perform check on which processes to receive data from and
>which processes to skip?
>if(id != master)
> MPI::COMM_WORLD.Send(&dist, NUM_VERTEX, MPI_LONG, master, 1234);
>if(id == master)
> for(int eachId = 1; eachId<procs ; eachId++)
> MPI::COMM_WORLD.Recv(&dist1, NUM_VERTEX, MPI_LONG, eachId, 1234);
One option is to have each non-master process send a "forget about me"
message. In practice, what this means is that every non-master process
does, in fact, send a message, with that message either containing data
or an indication that there is no data to send.