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From: John Robinson (jr_at_[hidden])
Date: 2006-02-28 09:46:48


Your MPI_Recv is trying to receive from the slave(1), not the master (0).

Jose Pedro Garcia Mahedero wrote:
> Hello everybody.
>
> I'm new to MPI and I'm having some problems while runnig a simple
> pingpong program in more than one node.
>
> 1.- I followed all the instructions and installed open MPI without
> problems in a Beowulf cluster.
> 2.- Ths cluster is working OK and ssh keys are set for not password
> prompting
> 3.- miexec seems to run OK.
> 4.- Now I'm using just 2 nodes: I've tried a simple ping-pong
> application but my master only sends one request!!
> 5.- I reduced the problem by trying to send just two mesages to the same
> node:
>
> int main(int argc, char **argv){
> int myrank;
>
> /* Initialize MPI */
>
> MPI_Init(&argc, &argv);
>
> /* Find out my identity in the default communicator */
>
> MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
> if (myrank == 0) {
> int work = 100;
> int count=0;
> for (int i =0; i < 10; i++){
> cout << "MASTER IS SLEEPING..." << endl;
> sleep(3);
> cout << "MASTER AWAKE WILL SEND["<< count++ << "]:" << work << endl;
> MPI_Send(&work, 1, MPI_INT, 1, WORKTAG, MPI_COMM_WORLD);
> }
> } else {
> int count =0;
> int work;
> MPI_Status status;
> while (true){
> MPI_Recv(&work, 1, MPI_INT, 0, MPI_ANY_TAG, MPI_COMM_WORLD,
> &status);
> cout << "SLAVE[" << myrank << "] RECEIVED[" << count++ << "]:"
> << work <<endl;
> if (status.MPI_TAG == DIETAG) {
> break;
> }
> }// while
> }
> MPI_Finalize();
>
>
>
> 6a.- RESULTS (if I put more than one machine in my mpihostsfile), my
> master sends the first message and my slave receives it perfectly. But
> my master doesnt send its second .
> message:
>
>
>
> Here's my output
>
> MASTER IS SLEEPING...
> MASTER AWAKE WILL SEND[0]:100
> MASTER IS SLEEPING...
> SLAVE[1] RECEIVED[0]:100MPI_STATUS.MPI_ERROR:0
> MASTER AWAKE WILL SEND[1]:100
>
> 6b.- RESULTS (if I put ONLY 1 machine in my mpihostsfile), everything
> is OK until iteration 9!!!
> MASTER IS SLEEPING...
> MASTER AWAKE WILL SEND[0]:100
> MASTER IS SLEEPING...
> MASTER AWAKE WILL SEND[1]:100
> MASTER IS SLEEPING...
> MASTER AWAKE WILL SEND[2]:100
> MASTER IS SLEEPING...
> MASTER AWAKE WILL SEND[3]:100
> MASTER IS SLEEPING...
> MASTER AWAKE WILL SEND[4]:100
> MASTER IS SLEEPING...
> MASTER AWAKE WILL SEND[5]:100
> MASTER IS SLEEPING...
> MASTER AWAKE WILL SEND[6]:100
> MASTER IS SLEEPING...
> MASTER AWAKE WILL SEND[7]:100
> MASTER IS SLEEPING...
> MASTER AWAKE WILL SEND[8]:100
> MASTER IS SLEEPING...
> MASTER AWAKE WILL SEND[9]:100
> SLAVE[1] RECEIVED[0]:100MPI_STATUS.MPI_ERROR:0
> SLAVE[1] RECEIVED[1]:100MPI_STATUS.MPI_ERROR:0
> SLAVE[1] RECEIVED[2]:100MPI_STATUS.MPI_ERROR:0
> SLAVE[1] RECEIVED[3]:100MPI_STATUS.MPI_ERROR:0
> SLAVE[1] RECEIVED[4]:100MPI_STATUS.MPI_ERROR:0
> SLAVE[1] RECEIVED[5]:100MPI_STATUS.MPI_ERROR:0
> SLAVE[1] RECEIVED[6]:100MPI_STATUS.MPI_ERROR:0
> SLAVE[1] RECEIVED[7]:100MPI_STATUS.MPI_ERROR:0
> SLAVE[1] RECEIVED[8]:100MPI_STATUS.MPI_ERROR:0
> SLAVE[1] RECEIVED[9]:100MPI_STATUS.MPI_ERROR:0
> --------------------------------
>
> I know this is a lot of text, but I wanted to give a mamixum detailed
> question. I've been search in FAQ, but still don't know what (and why)
> is going on...
>
> Anyone can help please :-) ?
>
>
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>
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