How to run a python code with mpirun

To test this example start a job with 2 nodes, see Fig. 1

Fig. 1.

Note: Carme uses carme_mpirun instead of mpirun. The former adds additional flags to the mpirun command.

1. As an example, create a cpp file:

   cd /home/<username> && touch hello_world.cpp
   

2. Copy the following code to the file:

   #include <stdio.h>
   #include <mpi.h>
   
   int main(int argc, char** argv){
      int process_Rank, size_Of_Cluster;
   
      MPI_Init(&argc, &argv);
      MPI_Comm_size(MPI_COMM_WORLD, &size_Of_Cluster);
      MPI_Comm_rank(MPI_COMM_WORLD, &process_Rank);
   
      printf("Hello World from process %d of %d\n", process_Rank, size_Of_Cluster);
   
      MPI_Finalize();
      return 0;
   }
   

3. Compile your file:

   mpic++ hello_world.cpp -o hello_world.exe
   

4. Run your executable file:

    carme_mpirun -np 2 ./hello_world.exe
   

5. The output shows that two processors were used:

   Hello, World from process 0 of 2.
   Hello, World from process 1 of 2.