Getting number of total MPI bytes transferred by a program

Question

Is there any way in MPI to get the total number of bytes transferred by my entire MPI program in C?

Answer 1

Not that I know of directly, but you could adapt the following code to your purposes:

uint64_t bytes_recv = 0;

void CommRecv(MyObject* a){
  MPI_Status status;

  MPI_Probe(MPI_ANY_SOURCE, MPI_ANY_TAG, MPI_COMM_WORLD, &status);

  int msg_size;
  MPI_Get_count(&status, MPI_BYTE, &msg_size);
  bytes_recv += msg_size;

  // Allocate a buffer to hold the incoming data
  char* buf = (char*)malloc(msg_size);
  assert(buf!=NULL);

  MPI_Recv(buf, msg_size, MPI_BYTE, from, MPI_ANY_TAG, MPI_COMM_WORLD, MPI_STATUS_IGNORE);

  //Do stuff

  free(buf);
}

The point here is to wrap the standard MPI communication functions with functions that keep track of data transfer statistics. Internally, these functions use MPI_Get_count() to retrieve the size of the incoming message. This is then added to a global variable that tracks communication over all of the wrapped MPI functions.

At the end of the program you can accumulate each instance's global variables on the master process.