[mpich-discuss] Problem with target_disp Parameter and 1-sided Messages

[Rajeev Thakur]

target_disp should be declared as an MPI_Aint. I am surprised the compiler didn't warn you.

Rajeev

On Jan 18, 2014, at 2:41 PM, "Corey A. Henderson" <cahenderson at wisc.edu>
 wrote:

> I am having a problem where I cannot set the target_disp parameter to a positive value in any of the 1-sided calls I've tried (EG: MPI_Put, MPI_Get, MPI_Fetch_and_op, etc.)
> 
> I am trying to use a shared (lock_all) approach with flushes. When I set target_disp to zero, the messaging works fine as expected. If I use a positive value I always get a Seg fault. 
> 
> Obligatory disclaimer: I am not a c or MPI expert so it's entirely possible I've made some newbie error here. But I am at my wit's end trying to figure this out and could use help.
> 
> Info: MPICH 3.0.4 built on Ubuntu 12.04 LTS running one node on Intel® Core™ i5-3570K CPU @ 3.40GHz × 4
> 
> I've attached the code I've isolated to show the problem. With the targetDisp int set to 0, the data is properly transferred. If it is set to 1, or sizeof(int), I get the following seg fault from mpiexec for targetDisp>0. 
> 
> corey at UbuntuDesktop:~/workspace/TargetDispBug/Release$ mpiexec -n 2 ./TargetDispBug
> 
> ===================================================================================
> =   BAD TERMINATION OF ONE OF YOUR APPLICATION PROCESSES
> =   EXIT CODE: 139
> =   CLEANING UP REMAINING PROCESSES
> =   YOU CAN IGNORE THE BELOW CLEANUP MESSAGES
> ===================================================================================
> YOUR APPLICATION TERMINATED WITH THE EXIT STRING: Segmentation fault (signal 11)
> This typically refers to a problem with your application.
> Please see the FAQ page for debugging suggestions
> 
> However, for targetDisp == 0 I get (as expected):
> 
> corey at UbuntuDesktop:~/workspace/TargetDispBug/Release$ mpiexec -n 2 ./TargetDispBug
> Received: 42.
> 
> The seg fault occurs at the MPI_Win_flush on both processes for targetDisp>0 on either the Put or Get or both. 
> 
> Any help with this would be great. 
> 
> Code follows:
> 
> #include "mpi.h"
> 
> int main(int argc, char* argv[]){
> 
>     // Test main for one sided message queueing
>     int rank, numranks, targetDisp = 0;
>     int sizeInBytes = 10*sizeof(int), *buffer;
>     MPI_Win window;
> 
>     MPI_Init(&argc, &argv);
> 
>     MPI_Comm_rank(MPI_COMM_WORLD, &rank);
>     MPI_Comm_size(MPI_COMM_WORLD, &numranks);
> 
>     MPI_Win_allocate(sizeInBytes, MPI_INT, MPI_INFO_NULL, MPI_COMM_WORLD, &buffer, &window);
> 
>     MPI_Win_lock_all(0, window);
> 
>     int *sendBuffer;
>     int *receiveBuffer;
> 
>     MPI_Alloc_mem(sizeof(int), MPI_INFO_NULL, &sendBuffer);
>     MPI_Alloc_mem(sizeof(int), MPI_INFO_NULL, &receiveBuffer);
> 
>     if (rank == 1) {
> 
>         sendBuffer[0] = 42;
> 
>         MPI_Put(sendBuffer, 1, MPI_INT, 0, targetDisp, 1, MPI_INT, window);
> 
>         MPI_Win_flush(0, window);
> 
>     }
> 
>     MPI_Barrier(MPI_COMM_WORLD);
> 
>     if (rank == 0) {
> 
>         MPI_Get(receiveBuffer, 1, MPI_INT, 0, targetDisp, 1, MPI_INT, window);
> 
>         MPI_Win_flush(0, window);
> 
>         printf("Received: %d.\n", receiveBuffer[0]);
> 
>     }
> 
>     MPI_Win_unlock_all(window);
> 
>     MPI_Free_mem(sendBuffer);
>     MPI_Free_mem(receiveBuffer);
> 
>     MPI_Win_free(&window);
> 
>     MPI_Finalize();
>     return 0;
> 
> }
> 
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