[mvapich-discuss] MPI continuous send and receive of messages in a loop

[Juan Vercellone]

On Sun, Oct 30, 2011 at 10:53 PM, roger federer <ooops.789 at gmail.com> wrote:
> well i am trying to do a program, where the process 0 should start the
> initialization of sending messages to a random process other than itself,
> then the random process selected should receive the message and send to
> another random process. This should happen until the requested number of
> messages to be sent is done, which is given by the user as input. I see that
> my program is either sending messages at the max 2 or else even none and
> giving me the following error
>
> ONE OF THE PROCESSES TERMINATED BADLY: CLEANING UP
> APPLICATION TERMINATED WITH THE EXIT STRING: Terminated (signal 15)
>
>
> Here is my code, lemme know whats the loop hole in it. The random generation
> part is not included, which is working fine
>
>
>     if(rank==0)
>     {
>     rnum=rgenerator(rank,size);
>     string++;
>     MPI_Send(&string, 50, MPI_INT, rnum, rnum, MPI_COMM_WORLD);
>     printf("\n process %d sends message to process %d",rank, rnum);
>
>     //MPI_Recv(&flag, 100, MPI_INT, MPI_ANY_SOURCE, MPI_ANY_TAG,
> MPI_COMM_WORLD, &status);
>
>     }
>
>         while(flag!=1)
>         {
>
>         if(MPI_Recv(&string, 50, MPI_INT, MPI_ANY_SOURCE, rank,
> MPI_COMM_WORLD, &status)==MPI_SUCCESS)
>         {
>
>             printf("\n process %d receives message from process %d count :
> %d",rank, status.MPI_SOURCE, string);
>             rnum=rgenerator(rank,size);
>             printf("\n Random num generated is %d",rnum);
>             string=string+1;
>             MPI_Send(&string, 50, MPI_INT, rnum, rnum, MPI_COMM_WORLD);
>             count++;
>
>             printf("\n process %d sends message to process %d", rank, rnum);
>
>             //MPI_Bcast(&count, 40, MPI_INT, rank, MPI_COMM_WORLD);
>             if(string==n)
>             {
>                 printf("\n\n Messages reached");
>                 flag=1;
>
>             }
>
>         }
>         else
>             flag=0;
>         }
>
>
>
>
> thank you.
>
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>
>

Note that the only process that will be exiting is the one that sends
when string == n. All the other processes will keep on executing the
program because they will not find the condition string == n, as
string continues to be incremented.

I think that an exit condition such as string >= n will do, but you
need to be aware of the exiting processes in order to avoid sending
data to anyone of them.

Regards,

-- 
---------- .-
VERCELLONE, Juan.
(also known as 1010ad1c97efb4734854b6ffd0899401)