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

#define	 ARRAYSIZE	300
#define  MASTER		0         /* taskid of first process */

int main(int argc,char **argv)
{
 int	   ntasks,           /* total number of MPI tasks in partitiion */
           nworkers,         /* number of worker tasks */
	   taskid,	         /* task identifier */
	   rc,               /* return error code */
	   dest,             /* destination task id to send message */
	   pares,
           index;            /* index into the array */
 
 long int  i, j, chunksize;  /* loop variable */
 
 int       arraymsg = 1,     /* setting a message type */
   	   indexmsg = 2,     /* setting a message type */
	   source;           /* origin task id of message */

 int	   data[ARRAYSIZE],     /* the intial array */
           result[ARRAYSIZE];    /* for holding results of array operations */
 
 MPI_Status status;


 srand ( time(NULL) );


 rc = MPI_Init(&argc,&argv);
 rc|= MPI_Comm_size(MPI_COMM_WORLD,&ntasks);
 rc|= MPI_Comm_rank(MPI_COMM_WORLD,&taskid);
 if (rc != MPI_SUCCESS)
    printf ("Error initializing MPI and obtaining task ID information\n");
 else
    printf ("\nMPI task ID = %d\n", taskid);
    fflush(stdout);
 //printf("%d tasks, I am task %d\n", ntasks, taskid);
 nworkers = ntasks-1;
 chunksize = (ARRAYSIZE / nworkers);


/**************************** master task ************************************/
 if (taskid == MASTER)
    { 
     printf("MASTER: number of worker tasks will be = %d\n",nworkers);
     fflush(stdout);
     
     
     for(i=0; i<ARRAYSIZE; i++) 
          data[i] = rand()%1000;
     index = 0;

     /* Send each worker task its portion of the array */
     for (dest=1; dest<= nworkers; dest++)
        { 
         printf("Sending to worker %d\n",dest);
         fflush(stdout);
	 	 
         //MPI_Send(buffer,count,type,dest,tag,comm)
         MPI_Send(&index, 1, MPI_INT, dest, indexmsg, MPI_COMM_WORLD);
         MPI_Send(&data[index], chunksize, MPI_INT, dest, arraymsg, MPI_COMM_WORLD);
         index = index + chunksize;
 
	 printf("Send to worker %d ended\n",dest);
         fflush(stdout);
        }

     // Now wait to receive back the results from each worker task and print 
     // a few sample values 
     for (i=1; i<= nworkers; i++)
        {
         source = i;
         MPI_Recv(&index, 1, MPI_INT, source, indexmsg, MPI_COMM_WORLD, &status);
         MPI_Recv(&result[index], chunksize, MPI_INT, source, arraymsg, MPI_COMM_WORLD, &status);
     
	 printf("Receiving from worker %d\n",i);
	 fflush(stdout);     
	}
	
     
     pares = 0;
      
     for(i=0; i<ARRAYSIZE; i++)
       {
	if (result[i] == 1) 
	  {
           printf("[%d] - ", data[i]);
           pares++;
	   if((pares % 10 == 0) || (pares == 0))
	     printf("\n");
	  }
	fflush(stdout);
        }
      printf("\n\nNumero de pares = %d\n", pares);
      printf("MASTER: All Done! \n");
   }

/**************************** worker task ************************************/

 if (taskid > MASTER)
   {   
    // Receive my portion of array from the master task 
    source = MASTER;
    //MPI_Recv(buffer,count,type,source,tag,comm,status) 
    MPI_Recv(&index, 1, MPI_INT, source, indexmsg, MPI_COMM_WORLD, &status);
    MPI_Recv(&result[index], chunksize, MPI_INT, source, arraymsg, MPI_COMM_WORLD, &status);
 
    printf("Escravo %d: recebeu tarefa\n", taskid);
    fflush(stdout);
    
    // Do a simple value assignment to each of my array elements 
    for(i=index; i< index + chunksize; i++)
       {
	if((result[i] % 2) == 0) result[i] = 1;
	else result[i] = 0;
       }       

    // Send my results back to the master task 
    dest = MASTER;
    MPI_Send(&index, 1, MPI_INT, dest, indexmsg, MPI_COMM_WORLD);
    MPI_Send(&result[index], chunksize, MPI_INT, MASTER, arraymsg, MPI_COMM_WORLD);
    printf("Escravo %d: finalizou tarefa\n", taskid);
    fflush(stdout);
   }
 MPI_Finalize();
}