-/* A first simple SPMD example program using MPI */
+#include <stdio.h>
+#include <mpi.h>
-/* The program consists of on receiver process and N-1 sender */
-/* processes. The sender processes send a message consisting */
-/* of their process identifier (id) and the total number of */
-/* processes (ntasks) to the receiver. The receiver process */
-/* prints out the values it receives in the messeges from the */
-/* senders. */
+int main(int argc, char *argv[])
+{
+ int rank, size, err;
-/* Compile the program with 'mpicc first.c -o first' */
-/* To run the program, using four of the computers specified in */
-/* your hostfile, do 'mpirun -machinefile hostfile -np 4 first */
+ err = MPI_Init(&argc, &argv); /* Initialize MPI */
+ if (err != MPI_SUCCESS) {
+ printf("MPI initialization failed!\n");
+ exit(1);
+ }
-#include <stdio.h>
-#include <mpi.h>
-main(int argc, char *argv[]) {
- const int tag = 42; /* Message tag */
- int id, ntasks, source_id, dest_id, err, i;
- MPI_Status status;
- int msg[2]; /* Message array */
-
- err = MPI_Init(&argc, &argv); /* Initialize MPI */
- if (err != MPI_SUCCESS) {
- printf("MPI initialization failed!\n");
- exit(1);
- }
- err = MPI_Comm_size(MPI_COMM_WORLD, &ntasks); /* Get nr of tasks */
- err = MPI_Comm_rank(MPI_COMM_WORLD, &id); /* Get id of this process */
- if (ntasks < 2) {
- printf("You have to use at least 2 processors to run this program\n");
- MPI_Finalize(); /* Quit if there is only one processor */
- exit(0);
- }
-
- if (id == 0) { /* Process 0 (the receiver) does this */
- for (i=1; i<ntasks; i++) {
- err = MPI_Recv(msg, 2, MPI_INT, MPI_ANY_SOURCE, tag, MPI_COMM_WORLD, \
- &status); /* Receive a message */
- source_id = status.MPI_SOURCE; /* Get id of sender */
- printf("Received message %d %d from process %d\n", msg[0], msg[1], \
- source_id);
- }
- }
- else { /* Processes 1 to N-1 (the senders) do this */
- msg[0] = id; /* Put own identifier in the message */
- msg[1] = ntasks; /* and total number of processes */
- dest_id = 0; /* Destination address */
- sleep(3);
- err = MPI_Send(msg, 2, MPI_INT, dest_id, tag, MPI_COMM_WORLD);
- }
-
- err = MPI_Finalize(); /* Terminate MPI */
- if (id==0) printf("Ready\n");
- return 0;
-}
+ err = MPI_Comm_size(MPI_COMM_WORLD, &size);
+ if (err != MPI_SUCCESS) {
+ printf("MPI Get Communicator Size Failed!\n");
+ }
+ err = MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+ if (err != MPI_SUCCESS) {
+ printf("MPI Get Communicator Rank Failed!\n");
+ }
+
+ if (0 == rank) {
+ printf("root node believes there are %d nodes in world.\n", size);
+ }
+
+ sleep(20);
+
+ err = MPI_Finalize(); /* Terminate MPI */
+ return 0;
+}
