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

const int MAXITEMS = 10;

int main(int argc, char **argv)
{
    int size;
    int rank;
    int value;
    int root=0;
    int array[MAXITEMS];
    int i;
    int anytag =0;
    double totalsum=0.0;
    double reciprocal;
    MPI_Status status;
    
    MPI_Init(&argc, &argv);
    MPI_Comm_size(MPI_COMM_WORLD, &size);
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    if (rank == 0)
    {
       srand(time(0));
       for (i = 1; i < size; i++)
       {
           value = rand() % 10;
           printf("Root process 0 sending %d to process %d\n", value, i);
	   MPI_Send(&value, 1, MPI_INT, i, anytag, MPI_COMM_WORLD);
	}
	
       value = rand() % 10;
       if (value == 0)
          reciprocal = 0;
       else reciprocal = 1.0/value;
       printf("Root process 0, value = %d, reciprocal = %lf\n", 
               value, reciprocal);
     }
     else {
         MPI_Recv(&value, 1, MPI_INT, 0, anytag, MPI_COMM_WORLD, &status);
         printf("Hello from process %d out of %d Received: %d\n", 
               rank, size, value);
	 if (value == 0)
	    reciprocal = 0.0;
	  else reciprocal = 1.0/ value; 
         printf("Process %d sending reciprocal (of %d) %lf to root 0", 
	         rank, value, reciprocal);
	 MPI_Send(&reciprocal, 1, MPI_DOUBLE, 0, anytag, MPI_COMM_WORLD);
         printf("\n");
     }
     MPI_Reduce(&reciprocal, &totalsum, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);
     if (rank == 0)
         printf("*** Reporting from ROOT: Totalsum of reciprocals = %lf ***\n",
	         totalsum);
     
     MPI_Finalize();
     return 0;
}

/*
mpicc -o reduceMPI reduceMPI.c 
mpirun N reduceMPI
Root process 0 sending 5 to process 1
Root process 0 sending 2 to process 2
Root process 0 sending 9 to process 3
Root process 0 sending 4 to process 4
Root process 0 sending 4 to process 5
Root process 0, value = 4, reciprocal = 0.250000
Hello from process 2 out of 6 Received: 2
Process 2 sending reciprocal (of 2) 0.500000 to root 0
Hello from process 3 out of 6 Received: 9
Process 3 sending reciprocal (of 9) 0.111111 to root 0
Hello from process 5 out of 6 Received: 4
Process 5 sending reciprocal (of 4) 0.250000 to root 0
Hello from process 1 out of 6 Received: 5
*** Reporting from ROOT: Totalsum of reciprocals = 1.561111 ***
Hello from process 4 out of 6 Received: 4
Process 4 sending reciprocal (of 4) 0.250000 to root 0
Process 1 sending reciprocal (of 5) 0.200000 to root 0


*/