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 <[email protected]> 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@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@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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