/*
 ============================================================================
 Name        : Laborator1.c
 Author      :
 Version     :
 Copyright   : Your copyright notice
 Description : Calculate Pi in MPI
 ============================================================================
 */
#include <mpi.h>
#include <stdio.h>
#include <string.h>

void
calc_pi(int rank, int num_procs)
{
    int     i;
    int     num_intervals;
    double  h;
    double  mypi;
    double  pi;
    double  sum;
    double  x;


    /* set number of intervals to calculate */
    if (rank == 0) {
        num_intervals = 100000000;
    }

    /* tell other tasks how many intervals */
    MPI_Bcast(&num_intervals, 1, MPI_INT, 0, MPI_COMM_WORLD);

    /* now everyone does their calculation */

    h = 1.0 / (double) num_intervals;
    sum = 0.0;

    for (i = rank + 1; i <= num_intervals; i += num_procs) {
        x = h * ((double)i - 0.5);
        sum += (4.0 / (1.0 + x*x));
    }

    mypi = h * sum;

    /* combine everyone's calculations */
    MPI_Reduce(&mypi, &pi, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);

    if (rank == 0) {
        printf("PI is approximately %.16f\n", pi);
    }
}

int
main(int argc, char *argv[])
{
    int         my_rank;        /* rank of process */
    int         n;      /* number of processes */
    int         source;         /* rank of sender */
    int         dest = 0;       /* rank of receiver */
    int         tag = 0;        /* tag for messages */
    char        message[100];   /* storage for message */
    MPI_Status  status ;        /* return status for receive */

    int m = 3;
    int s = 0;
    int A[8] = {3,7,15,19,30,4,1,72};
    int mask = 0;
    int i = 0;
    int sr;
    s = A[my_rank];
    mask = 0;

    /* start up MPI */

    MPI_Init(&argc, &argv);

    /* find out process rank */
    MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);

    /* find out number of processes */
    MPI_Comm_size(MPI_COMM_WORLD, &n);


    for (i= 0; i<m-1; i++)
    {
        if (my_rank && mask == 0)
        {
            if (my_rank && 2<<i == 0)
            {
                source = my_rank^ 2<<i;

                //receive sr from source
                MPI_Recv(sr, 1, MPI_INT, source, tag,MPI_COMM_WORLD,&status);

                printf("%d <= \"%d\"\n",my_rank, sr);

                s = s + sr;
            }
            else
            {
                dest = my_rank^ 2<<i ;

                //send s to destination
                MPI_Send(s,1, MPI_INT,dest, tag, MPI_COMM_WORLD);

                printf("%d => \"%d\"\n",my_rank,s);

            }
        }

        //mask ← mask xor 2i
        mask = mask^2<<i;
    }

    printf("sum is = %d",s);

    /* calculate PI */
    calc_pi(my_rank, n);

    /* shut down MPI */
    MPI_Finalize();

    return 0;
}