Parallel Program to add numbers from 1 to n using MPI

parallel_add.c

// This program adds numbers from 1 to n using MPI
// Sample Execution code : mpirun -n 4 ./a.out 100 ; Here 100 represents n 

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

int main(int argc, char **argv)
{

    int id, nproc;
    int sum, startval, endval, partial_sum;
    int num = atoi(argv[1]);

    MPI_Init(&argc, &argv);

    // Total number of process
    MPI_Comm_size(MPI_COMM_WORLD, &nproc);

    // get id of mynode:
    MPI_Comm_rank(MPI_COMM_WORLD, &id);
    MPI_Status status;

    sum = 0; // zero sum for accumulation

    // Spilt the numbers among different processes
    startval = num * id / nproc + 1;
    endval = num * (id + 1) / nproc;

    for (int i = startval; i <= endval; ++i)
        sum = sum + i;

    printf("I am the Process %d and my partial sum is %d \n", id, sum);

    if (id != 0) //the slaves sending back the partial sums
        MPI_Send(&sum, 1, MPI_INT, 0, 1, MPI_COMM_WORLD);

    else //id==0! the master recieves the partial sums
    {
        printf("\n\nI am master and my sum currently is : %d\n", sum);
        for (int j = 1; j < nproc; j++)
        {
            MPI_Recv(&partial_sum, 1, MPI_INT, j, 1, MPI_COMM_WORLD, &status);
            sum = sum + partial_sum;
            printf("The sum yet is %d after adding sum %d from process %d\n", sum, partial_sum, j);
        }
    }
    if (id == 0)
        printf("The sum from 1 to %d is %d \n\n", num, sum);

    MPI_Finalize();
}

parallel_add_timed.c

// This program calculates the time required to add numbers from 1 to n using MPI
// Sample Execution code : mpirun -n 4 ./a.out 100 ; Here 100 represents n 

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

int main(int argc, char **argv)
{

    int id, nproc;
    int sum, startval, endval, partial_sum;
    int num = atoi(argv[1]);
    double start_time, max_time, total_time, min_time;

    MPI_Init(&argc, &argv);

    // Total number of process
    MPI_Comm_size(MPI_COMM_WORLD, &nproc);

    // get id of mynode:
    MPI_Comm_rank(MPI_COMM_WORLD, &id);
    MPI_Status status;

    sum = 0; // zero sum for accumulation

    MPI_Barrier(MPI_COMM_WORLD); /*synchronize all processes*/
    start_time = MPI_Wtime();

    // Spilt the numbers among different processes
    startval = num * id / nproc + 1;
    endval = num * (id + 1) / nproc;

    for (int i = startval; i <= endval; ++i)
        sum = sum + i;

    // printf("I am the Process %d and my partial sum is %d \n", id, sum);
    if (id != 0) //the slaves sending back the partial sums
        MPI_Send(&sum, 1, MPI_INT, 0, 1, MPI_COMM_WORLD);

    else //id==0! the master recieves the partial sums
    {
        // printf("\n\nI am master and my sum currently is : %d\n", sum);
        for (int j = 1; j < nproc; j++)
        {
            MPI_Recv(&partial_sum, 1, MPI_INT, j, 1, MPI_COMM_WORLD, &status);
            sum = sum + partial_sum;
            // printf("The sum yet is %d after adding sum %d from process %d\n", sum, partial_sum, j);
        }
    }
    total_time = MPI_Wtime() - start_time;

    MPI_Reduce(&total_time, &max_time, 1, MPI_DOUBLE, MPI_MAX, 0, MPI_COMM_WORLD);
    MPI_Reduce(&total_time, &min_time, 1, MPI_DOUBLE, MPI_MIN, 0, MPI_COMM_WORLD);

    if (id == 0)
    {
        // printf("The sum from 1 to %d is %d \n\n", sum, num);
        printf("Minimum Time (any processor) = %f \n"
               "Maximum Time (any processor) = %f \n",
               min_time, max_time);
    }

    MPI_Finalize();
}