source: TOOLS/SURPACK_IPSL/cmd_launch.c @ 3624

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

#define CMD_MAXLEN 4096
#define CMD_MASTER 0
#define TAG_AVAIL 1
#define TAG_CMD   2

void read_and_exec(char *filename);
void read_and_send(int slaves, char *filename);
void recv_and_exec(int rank);
void read_next_command(FILE *fl, char *cmd);
void exec_command(char *cmd, int rank);

int main(int argc,char **argv)
{
        FILE *fl;
        int rank,size;

        MPI_Init(&argc,&argv);
        MPI_Comm_rank(MPI_COMM_WORLD,&rank);
        MPI_Comm_size(MPI_COMM_WORLD,&size);  
        if (rank == CMD_MASTER)
                printf("master is %d , nb slaves: %d\n",
                       CMD_MASTER,size-1);      

        if (size == 1)
                read_and_exec(argv[1]);
        else if(size != 1 && rank == CMD_MASTER)
                read_and_send(size-1,argv[1]);
        else
                recv_and_exec(rank);
        MPI_Finalize();
}

void read_and_exec(char *filename)
{
        FILE *fl;
        char cmd[CMD_MAXLEN];
        double t;

        fl = fopen(filename,"r");
        do {
          read_next_command(fl,cmd);
                if(!strlen(cmd))
                        break;
                exec_command(cmd,CMD_MASTER);
        } while (strlen(cmd));
        fclose(fl);
}

void read_and_send(int slaves,char *filename)
{
        int i, num;
        MPI_Status status;
        FILE *fl;
        char cmd[CMD_MAXLEN];

        fl = fopen(filename,"r");
        i=0;
        do {
                read_next_command(fl,cmd);
                MPI_Recv(&num,1,MPI_INT,MPI_ANY_SOURCE,
                         TAG_AVAIL,MPI_COMM_WORLD,&status);
                MPI_Send(cmd,CMD_MAXLEN,MPI_CHAR,num,
                         TAG_CMD,MPI_COMM_WORLD);
                if (!strlen(cmd)) /* terminate command sent */
                        i++;
        } while (i < slaves);
        fclose(fl);
}

void recv_and_exec(int rank)
{
        char cmd[CMD_MAXLEN];  
        MPI_Status status;  

        do {
                MPI_Send(&rank,1,MPI_INT,CMD_MASTER,
                         TAG_AVAIL,MPI_COMM_WORLD); 
                MPI_Recv(cmd,CMD_MAXLEN,MPI_CHAR,CMD_MASTER,
                         TAG_CMD,MPI_COMM_WORLD,&status); 
                if(!strlen(cmd)) /* terminate command */
                        break;
                exec_command(cmd,rank);
        } while (strlen(cmd));
}

void read_next_command(FILE *fl,char *cmd)
{
        if(!fgets(cmd,CMD_MAXLEN,fl)) cmd[0]='\0';
        if(cmd[strlen(cmd)-1]=='\n') cmd[strlen(cmd)-1]='\0';
}

void exec_command(char *cmd, int rank)
{
        double t;
        int r;

        t = MPI_Wtime();  
        r=system(cmd);
        t = MPI_Wtime() - t;  
        fprintf(stderr,"#executed by process\t%d in %gs\twith status\t%d : %s\n",
                rank,t,r,cmd);
}