#include <stdio.h>
#include </usr/lib64/mpi/gcc/openmpi/include/mpi.h>
#include <math.h>

#define PRECISION 0.000001
#define RANGESIZE 1
#define DATA 0
#define RESULT 1
#define FINISH 2

#define DEBUG
double f(double x) {
    return sin(x)*sin(x)/x;
}
double SimpleIntegration(double a,double b) {
    double i;
    double sum=0;
    for (i=a; i<b; i+=PRECISION)
        sum+=f(i)*PRECISION;
    return sum;
}
int main(int argc, char **argv) {
    int myrank,proccount;
    double a=1,b=100;
    double range[2];
    double result=0,resulttemp;
    int sentcount=0;
    int i;
    int flag;
    double time;
    MPI_Status status;
    // Initialize MPI
    MPI_Init(&argc, &argv);
    // find out my rank
    MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
    // find out the number of processes in MPI_COMM_WORLD
    MPI_Comm_size(MPI_COMM_WORLD, &proccount);
    if (proccount<2) {
        printf("Run with at least 2 processes");
        MPI_Finalize();
        return -1;
    }
    if (((b-a)/RANGESIZE)<4*(proccount-1)) {
        printf("More subranges needed");
        MPI_Finalize();
        return -1;
    }
    // now the master will distribute the data and slave processes will perform computations
    if (myrank==0) {
        range[0]=a;
        // first distribute some ranges to all slaves
        for(i=2; i<proccount*2; i++) {
            range[1]=range[0]+RANGESIZE;
#ifdef DEBUG
            printf("\nMaster sending range %f,%f to process %d",range[0],range[1],i/2);
            fflush(stdout);
#endif
            // send it to process i
            MPI_Send(range,2,MPI_DOUBLE,i/2,DATA,MPI_COMM_WORLD);
            sentcount++;
            range[0]=range[1];
        }


        do {
            // distribute remaining subranges to the processes which have completed their parts
            //***************************************************************************
            // ODBIERZMY WSZYSTKO CO JEST DO ODEBRANIA
            for (;;) {
                MPI_Iprobe(MPI_ANY_SOURCE,RESULT,MPI_COMM_WORLD,&flag, &status);
                if (flag == 0) {
                    break;
                }
                MPI_Recv(&resulttemp,1,MPI_DOUBLE,MPI_ANY_SOURCE,RESULT,MPI_COMM_WORLD,&status);
                result+=resulttemp;
#ifdef DEBUG
                printf("\nMaster received result %f from process %d",resulttemp,status.MPI_SOURCE);
                fflush(stdout);
#endif
                // check the sender and send some more data
                range[1]=range[0]+RANGESIZE;
                if (range[1]>b) range[1]=b;
#ifdef DEBUG
                printf("\nMaster sending range %f,%f to process %d",range[0],range[1],status.MPI_SOURCE);
                fflush(stdout);
#endif
                MPI_Send(range,2,MPI_DOUBLE,status.MPI_SOURCE,DATA,MPI_COMM_WORLD);
                range[0]=range[1];
            }
            //***************************************************************************
            // MASTER LICZY TU SOBIE SWOJA PORCJE
            range[1]=range[0]+RANGESIZE;
            if (range[1]>b) range[1]=b;

            result+=SimpleIntegration(range[0],range[1]);

            range[0]=range[1];

        } while (range[1]<b);
        // now receive results from the processes
        for(i=2; i<proccount*2; i++) {
            time = MPI_Wtime();

            MPI_Recv(&resulttemp,1,MPI_DOUBLE,MPI_ANY_SOURCE,RESULT,MPI_COMM_WORLD,&status);
#ifdef DEBUG
            printf("\nMaster received result %f from process %d, in time: %f",resulttemp,status.MPI_SOURCE, MPI_Wtime()-time);
            fflush(stdout);
#endif
            result+=resulttemp;
        }
        // shut down the slaves
        for(i=1; i<proccount; i++) {
            MPI_Send(NULL,0,MPI_DOUBLE,i,FINISH,MPI_COMM_WORLD);
        }
        // now display the result
        printf("\nHi, I am process 0, the result is %f\n",result);
    }
    // ***************************************




    else {
        // slave
        // this is easy - just receive data and do the work
        do {
            time = MPI_Wtime();
            MPI_Iprobe(0,MPI_ANY_TAG,MPI_COMM_WORLD,&flag, &status);
            if (0 == flag) {
                continue;
            }
            printf("\nSlave %d waited %f for message",myrank,MPI_Wtime()-time);
            if (status.MPI_TAG==DATA) {


                MPI_Recv(range,2,MPI_DOUBLE,0,DATA,MPI_COMM_WORLD,&status);
                printf("\nSlave received range: %f %f\n", range[0], range[1]);

// compute my part
                resulttemp=SimpleIntegration(range[0],range[1]);
// send the result back
                MPI_Send(&resulttemp,1,MPI_DOUBLE,0,RESULT,MPI_COMM_WORLD);
            }
        } while (status.MPI_TAG!=FINISH);
    }
    // Shut down MPI
    MPI_Finalize();
    return 0;
}