[mpich-discuss] Please explain

[Andreas Schäfer]

Hi Soheil,

first of all, it is considered good style to post complete, minimal,
programs, not just excerpts, so that others can quickly reproduce the
problem you're reporting.

To solve your homework, consider the following hints: 1. which lines
of code does the for-loop enclose? 2. Which rank will send data to
which other rank? 3. Which rank will receive data from which remote
rank? (I'm using rank synonymous to process.)

Best
-Andreas


On 07:17 Sun 22 Dec     , Soheil Hooshdaran wrote:
> Hello.
> This program deadlocks and I cannot see the reason. Would you please
> explain it to me?
> 
> Thanks in advance
> 
> int send_buf[10];
>   int recv_buf[10];
>   int i;
>   for(i=0;i<world_size;++i)
>   if (world_rank == 0) {
>     // If we are rank 0, set the number to -1 and send it to process 1
>     printf("sent to process %d\n", i);
>     MPI_Send(send_buf, 10, MPI_INT, 1, 0, MPI_COMM_WORLD);
>   }
>     printf("process %d\n", world_rank);
>     MPI_Recv(recv_buf, 10, MPI_INT, 0, 0, MPI_COMM_WORLD,
> MPI_STATUS_IGNORE);
>     printf("Process %d received %d bytes from process 0\n", world_rank, 10);

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-- 
==========================================================
Andreas Schäfer
HPC and Grid Computing
Chair of Computer Science 3
Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
+49 9131 85-27910
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http://www.libgeodecomp.org
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