#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);
}