[mpich-discuss] Question reg usage with MPI_THREAD_MULTIPLE

[Ramesh Vinayagam]

It hangs at the pthread join of the second process, which did not make
sense because its the same way I use for the first process, also I use
different communicators for communication.


Thanks


On Mon, Jun 25, 2012 at 5:50 PM, Darius Buntinas <buntinas at mcs.anl.gov>wrote:

> I didn't test your program, but I didn't see any obvious problems.  MPICH
> does support using threads in the way you described.  What is the output
> you get?  Where does it hang?
>
> -d
>
>
> On Jun 25, 2012, at 5:58 PM, Ramesh Vinayagam wrote:
>
> > Hello,
> >
> >
> > I having a question regarding the usage of MPI_THREAD_MULTIPLE.
> >
> > I was wondering whether this scenario works with MPI
> >
> > Process 0
> > Thread 1 -> probes and receives
> > Thread 2 -> Sends to  process 0
> >
> > Process 1
> >
> > Thread 1 -> probes and receives
> > Thread 2 -> Sends to  process 1
> >
> > I wrote a simple code, and it seems to hang with mpich2. I am not sure
> whether or not this feature is supported with MPI, can anyone let me know
> whether what I do here is correct or wrong?
> >
> >
> > Here is the code.. This code hangs when I use it with two processes. It
> works with one process.
> >
> > Thanks
> > Ramesh
> >
> ____________________________________________________________________________________________________________________________________________________
> > #include <stdio.h>
> > #include <stdlib.h>
> > #include <mpi.h>
> > #include <string.h>
> > #include <assert.h>
> >
> > typedef struct
> > {
> >   int thread;
> >   MPI_Comm comm;
> >   int rank;
> > } thdata;
> >
> > void probe_recv (void *ptr){
> >   thdata *data;
> >   data = (thdata *) ptr;
> >   int count, flag = 0;
> >   MPI_Status status;
> >   char buf[256];
> >
> >   printf("%d :Thread :%d Prbes and receives \n", data->rank,
> data->thread);
> >   while (!flag){
> >     MPI_Iprobe(data->rank, 0, data->comm, &flag, &status);
> >   }
> >   MPI_Get_count( &status, MPI_CHAR, &count);
> >   printf("%d :Thread :%d count : %d \n", data->rank, data->thread,
> count);
> >
> >   MPI_Recv( &buf,
> >           count,
> >           MPI_CHAR,
> >           data->rank,
> >           status.MPI_TAG,
> >           data->comm,
> >           MPI_STATUS_IGNORE);
> >
> >   printf("%d Message : %s \n", data->rank,buf);
> > }
> >
> > void send(void *ptr){
> >   thdata *data;
> >   char buffer[256];
> >   data = (thdata *) ptr;
> >   printf("%d: Thread :%d Sends \n", data->rank, data->thread);
> >   strcpy(buffer,"Hello World");
> >   MPI_Send(&buffer,256, MPI_CHAR, data->rank, 0, data->comm);
> >   printf("%d: Thread :%d send completed \n",
> >        data->rank,
> >        data->thread);
> > }
> >
> >
> > int main(int argc, char *argv[]){
> >
> >   int provided, i[2], rank, size;
> >   MPI_Status  status;
> >   pthread_t thread_a, thread_b;
> >   MPI_Comm communicator[2];
> >   thdata data1, data2;
> >
> >   MPI_Init_thread(&argc, &argv, MPI_THREAD_MULTIPLE, &provided);
> >
> >   if (provided != MPI_THREAD_MULTIPLE){
> >       printf("Error\n");
> >       MPI_Abort(911, MPI_COMM_WORLD);
> >   }
> >   MPI_Comm_rank(MPI_COMM_WORLD, &rank);
> >   MPI_Comm_size(MPI_COMM_WORLD, &size);
> >   assert (size == 2);
> >   MPI_Comm_dup(MPI_COMM_WORLD,&communicator[rank]);
> >
> >   data1.comm = communicator[rank];
> >   data1.thread = 1;
> >   data1.rank = rank;
> >   pthread_create (&thread_a, NULL, (void *) &probe_recv, (void *)&data1);
> >
> >   data2.comm = communicator[rank];
> >   data2.thread = 2;
> >   data2.rank = rank;
> >   pthread_create (&thread_b, NULL, (void *) &send, (void *)&data2);
> >
> >   pthread_join(thread_a, NULL);
> >   pthread_join(thread_b, NULL);
> >   MPI_Finalize();
> > }
> >
> >
> >
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