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

[Jeff Hammond]

Hi Corey,

It was a simple bug.  You passed MPI_INT as the disp_unit rather than
sizeof(int), which is almost certainly what you meant.  MPI_INT is an
opaque handle that is 1275069445 when interpreted as an integer.

I am not entirely sure why using such a large disp_unit caused the
segfault though.  I haven't yet figured out where disp_unit is used in
the MPI_Get code.

Best,

Jeff

On Sat, 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;
>
> }
>
>
> _______________________________________________
> discuss mailing list     discuss at mpich.org
> To manage subscription options or unsubscribe:
> https://lists.mpich.org/mailman/listinfo/discuss



-- 
Jeff Hammond
jeff.science at gmail.com