MPI not receiving the same buffer I sent with blocking send/recv

Question

I am not receiving the same buffer I sent. Even with blocking Send/Recv. I use contigously allocated buffers.

I basically change the 1st row in that buffer in every message. The buffer with a change is OK after send by the master, but it's wrong after I receive it in a slave.

I have already spent more than 15 hours on this. Any help is appreciated.

Here is the lot of my messages in 1 master + 1 slave situation. Notice how the 1st line at master changes but rest of the buffer remains the same. At slave's side the rest of the buffer changes too. There it is: log messages

size_t order = 0;
floattype **getWork(floattype **work, floattype **tmatrix)
{
     size_t tmp = 1;

     // leading row
     work[0] = tmatrix[order++];

     // get needed rows
     for(size_t row = 1; row < 5; row++)
     {
          work[tmp++] = tmatrix[row];
     }

     return work;
 }


void master(size_t chunksize, floattype **extendedmatrix, size_t paramcount, size_t rowcount)
{
     int ntasks, node;
     size_t reply;
     floattype **tmatrix = transponeMatrix(extendedmatrix, paramcount, rowcount);
     floattype **work = AllocMatrix(rowcount, chunksize + 1);


     MPI_Status status;
     MPI_Comm_size(MPI_COMM_WORLD, &ntasks);


     // init all slaves
     for (node = 1; node < ntasks; ++node) 
     {      
          getWork(work, tmatrix);

          MPI_Send(work[0], 32, MPI_DOUBLE, node, WORKTAG, MPI_COMM_WORLD);
     }

     size_t rpt = 0;

     while (rpt < 3) 
     {
        rpt++;
        MPI_Recv(&reply, 1, MPI_UNSIGNED_LONG, MPI_ANY_SOURCE, INFOTAG, MPI_COMM_WORLD, &status); 

        getWork(work, tmatrix);

        MPI_Send(work[0], 32, MPI_DOUBLE, status.MPI_SOURCE, WORKTAG, MPI_COMM_WORLD);  
     }
 }

void slave(size_t chunksize, size_t paramcount, size_t rowcount)
{
    floattype **received = AllocMatrix(rowcount, chunksize + 1);
        size_t reply = 0;

    MPI_Status status;

    while (true) {
         MPI_Recv(received[0], 32, MPI_DOUBLE, 0, MPI_ANY_TAG, MPI_COMM_WORLD, &status);

         // lets finish
         if (status.MPI_TAG == DIETAG) {
             FreeMatrix(received);

             return;
         }


         MPI_Send(&reply, 1, MPI_UNSIGNED_LONG, 0, INFOTAG, MPI_COMM_WORLD);
    }

}

Yuri Yuri · Accepted Answer · 2014-01-01T14:34:06

Wrong memory assignment... Should have used memcpy() to copy the memory blocks from one buffer to another in getWork().

MPI not receiving the same buffer I sent with blocking send/recv

1 Answers