The MPI_Init (with args of &argc and &argv. It is the requirement of MPI implementations) must be really the first executed statement of MAIN. And Finalize must be the very last executed statement.

main() will be started on every node in MPI environment. In argc and argv can be parameters like number of nodes, node_id, and master node address.

It is framework:

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

void f();

int numprocs; int myid; 

int main(int argc, char **argv)  
{  

MPI_Init(&argc, &argv);  
MPI_Comm_size(MPI_COMM_WORLD,&numprocs);  
MPI_Comm_rank(MPI_COMM_WORLD,&myid);  

if(myid == 0)  
{  /* main process. user interaction is ONLY HERE */

    printf("%s\n", "Start running!");  

    MPI_Send ... requests with job
    /*may be call f in main too*/
    MPU_Reqv ... results..
    printf("%s\n", "End running!");  
}
else
{

  /* Slaves. Do sit here and wait a job from main process */
  MPI_Recv(.input..);  
  /* dispatch input by parsing it 
    (if there can be different types of work)
    or just do the work */    
  f(..)
  MPI_Send(.results..);  
}

MPI_Finalize();  

return 0;  
}  

The MPI_Init (with args of &argc and &argv. It is the requirement of MPI implementations) must be really the first executed statement of MAIN. And Finalize must be the very last executed statement.

main() will be started on every node in MPI environment. Parameters like number of nodes, node_id, and master node address may be passed via argc and argv.

It is framework:

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

void f();

int numprocs; int myid; 

int main(int argc, char **argv)  
{  

MPI_Init(&argc, &argv);  
MPI_Comm_size(MPI_COMM_WORLD,&numprocs);  
MPI_Comm_rank(MPI_COMM_WORLD,&myid);  

if(myid == 0)  
{  /* main process. user interaction is ONLY HERE */

    printf("%s\n", "Start running!");  

    MPI_Send ... requests with job
    /*may be call f in main too*/
    MPU_Reqv ... results..
    printf("%s\n", "End running!");  
}
else
{

  /* Slaves. Do sit here and wait a job from main process */
  MPI_Recv(.input..);  
  /* dispatch input by parsing it 
    (if there can be different types of work)
    or just do the work */    
  f(..)
  MPI_Send(.results..);  
}

MPI_Finalize();  

return 0;  
}