#include <mpi.h>
#include <stdio.h>

#define CHKERRMPI(ierr)  do { if (ierr) MPI_Abort(MPI_COMM_WORLD,MPI_ERR_OTHER); } while (0)
int main(int argc, char** argv)
{
  int          ierr;
  MPI_Request  req[1];
  double       buf[4] = {.1,.2,.3,.4};
  MPI_Datatype dtype;
  int          rank,size,tag=100;

  ierr = MPI_Init(&argc,&argv);CHKERRMPI(ierr);
  ierr = MPI_Comm_rank(MPI_COMM_WORLD,&rank);CHKERRMPI(ierr);
  ierr = MPI_Comm_size(MPI_COMM_WORLD,&size);CHKERRMPI(ierr);

  if (size != 2) {
    if (!rank) printf("This test requires two MPI ranks\n");
    MPI_Abort(MPI_COMM_WORLD,MPI_ERR_COMM);
  }

  ierr = MPI_Type_contiguous(4,MPI_DOUBLE,&dtype);CHKERRMPI(ierr);
  ierr = MPI_Type_commit(&dtype);CHKERRMPI(ierr);
  if (!rank) {
    ierr = MPI_Send_init(buf,1,dtype,1,tag,MPI_COMM_WORLD,req);CHKERRMPI(ierr);
  } else {
    ierr = MPI_Recv_init(buf,1,dtype,0,tag,MPI_COMM_WORLD,req);CHKERRMPI(ierr);
  }

  for (int i=0; i<2; i++) {
    ierr = MPI_Startall(1,req);CHKERRMPI(ierr);
    ierr = MPI_Waitall(1,req,MPI_STATUSES_IGNORE);CHKERRMPI(ierr);
  }

  ierr = MPI_Type_free(&dtype);CHKERRMPI(ierr);
  ierr = MPI_Request_free(req);CHKERRMPI(ierr);
  ierr = MPI_Finalize();CHKERRMPI(ierr);
  return 0;
}