Send Recv Example

mpi_hosts

 master
-slave1
-slave2
+slave1 user=mpiuser
+slave2 user=mpiuser

send_recv.c

+#include <mpi.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(int argc, char** argv) {
+  // Initialize the MPI environment
+  MPI_Init(NULL, NULL);
+  // Find out rank, size
+  int world_rank;
+  MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);
+  int world_size;
+  MPI_Comm_size(MPI_COMM_WORLD, &world_size);
+
+  // We are assuming at least 2 processes for this task
+  if (world_size < 2) {
+    fprintf(stderr, "World size must be greater than 1 for %s\n", argv[0]);
+    MPI_Abort(MPI_COMM_WORLD, 1);
+  }
+
+  int number;
+  if (world_rank == 0) {
+    // If we are rank 0, set the number to -1 and send it to process 1
+    number = -1;
+    MPI_Send(
+      /* data         = */ &number, 
+      /* count        = */ 1, 
+      /* datatype     = */ MPI_INT, 
+      /* destination  = */ 1, 
+      /* tag          = */ 0, 
+      /* communicator = */ MPI_COMM_WORLD);
+  } else if (world_rank == 1) {
+    MPI_Recv(
+      /* data         = */ &number, 
+      /* count        = */ 1, 
+      /* datatype     = */ MPI_INT, 
+      /* source       = */ 0, 
+      /* tag          = */ 0, 
+      /* communicator = */ MPI_COMM_WORLD, 
+      /* status       = */ MPI_STATUS_IGNORE);
+    printf("Process 1 received number %d from process 0\n", number);
+  }
+  MPI_Finalize();
+}
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