source: CIVL/examples/messagePassing/mpi.cvl@ 30a979d

typedef $comm MPI_Comm;

typedef enum {
  MPI_INT,
  MPI_FLOAT,
  MPI_DOUBLE,
  MPI_CHAR
} MPI_Datatype;

#define BCAST_TAG 999

#define MPI_PROC_NULL -3

typedef struct {
  int MPI_SOURCE;
  int MPI_TAG;
  int MPI_ERROR;
  int size;
} MPI_Status;

#define MPI_STATUS_IGNORE NULL

#define MPI_STATUSES_IGNORE NULL

int sizeofDatatype(MPI_Datatype datatype) {
  switch (datatype) {
  case MPI_INT:
    return sizeof(int);
  case MPI_FLOAT:
    return sizeof(float);
  case MPI_DOUBLE:
    return sizeof(double);
  case MPI_CHAR:
    return sizeof(char);
  default:
    $assert(0, "Unreachable");
  }
}

int MPI_Init() {
  return 0;
}

int MPI_Finalize() {
  return 0;
}

int MPI_Comm_size(MPI_Comm comm, int *size) {
  *size = $comm_size(comm);
  return 0;
}

int MPI_Comm_rank(MPI_Comm comm, int *rank) {
  *rank = $comm_place(comm);
  return 0;
}

/* Sends a message. */
int MPI_Send(void *buf, int count, MPI_Datatype datatype, int dest,
             int tag, MPI_Comm comm) {
  if (dest >= 0) {
    int size = count*sizeofDatatype(datatype);
    $message out =
      $message_pack(comm->place, dest, tag, buf, size);

    $comm_enqueue(comm, out);
  }
  return 0;
}

/* Receives a message. */
int MPI_Recv(void *buf, int count, MPI_Datatype datatype, int source,
             int tag, MPI_Comm comm, MPI_Status *status) {
  if (source >= 0) {
    $message in = $comm_dequeue(comm, source, tag);
    int size = count*sizeofDatatype(datatype);

    $message_unpack(in, buf, size);
    if (status != MPI_STATUS_IGNORE) {
      status->size = $message_size(in);
      status->MPI_SOURCE = $message_source(in);
      status->MPI_TAG = $message_tag(in);
      status->MPI_ERROR = 0;
    }
  }
  return 0;
}

int MPI_Get_count(MPI_Status *status, MPI_Datatype datatype, int *count) {
  *count = status->size/sizeofDatatype(datatype);
  return 0;
}

int MPI_Sendrecv(void *sendbuf, int sendcount, MPI_Datatype sendtype,
                 int dest, int sendtag,
                 void *recvbuf, int recvcount, MPI_Datatype recvtype,
                 int source, int recvtag,
                 MPI_Comm comm, MPI_Status *status) {
  MPI_Send(sendbuf, sendcount, sendtype, dest, sendtag, comm);
  MPI_Recv(recvbuf, recvcount, recvtype, source, recvtag, comm, status);
  return 0;
}

/* Broadcasts a message from root to everyone else.
 * Need to use a differnt comm.
 */
int MPI_Bcast(void *buf, int count, MPI_Datatype datatype, int root,
              MPI_Comm comm) {
  

  int place = $comm_place(comm);

#ifdef DEBUG
  printf("MPI_Bcast: place=%d, count=%d, root=%d\n", place, count, root);
#endif
  if (place == root) {
    int nprocs = $comm_size(comm);

    for (int i=0; i<nprocs; i++)
      if (i != root)
        MPI_Send(buf, count, datatype, i, BCAST_TAG, comm);
  } else {
    MPI_Recv(buf, count, datatype, root, BCAST_TAG, comm, MPI_STATUS_IGNORE);
  }
  return 0;
}