OS-II Assignment No. 4: Distributed and mobile OS

 Operating System-II 

Assignment No. 4: Distributed and mobile OS

Slot-I

i. Write an MPI program to calculates sum of randomly generated 1000 numbers (stored in array) on a cluster

Solution:-

#include <mpi.h>

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

// size of array

#define n 10

int a[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

// Temporary array for slave process

int a2[1000];

int main(int argc, char* argv[])

{

int pid, np,

elements_per_process,

n_elements_recieved;

// np -> no. of processes

// pid -> process id

MPI_Status status;

// Creation of parallel processes

MPI_Init(&argc, &argv);

// find out process ID,

// and how many processes were started

MPI_Comm_rank(MPI_COMM_WORLD, &pid);

MPI_Comm_size(MPI_COMM_WORLD, &np);

// master process

if (pid == 0) {

int index, i;

elements_per_process = n / np;

// check if more than 1 processes are run

if (np > 1) {

// distributes the portion of array

// to child processes to calculate

// their partial sums

for (i = 1; i < np - 1; i++) {

index = i * elements_per_process;

MPI_Send(&elements_per_process,

1, MPI_INT, i, 0,

MPI_COMM_WORLD);

MPI_Send(&a[index],

elements_per_process,

MPI_INT, i, 0,

MPI_COMM_WORLD);

}

// last process adds remaining elements

index = i * elements_per_process;

int elements_left = n - index;

MPI_Send(&elements_left,

1, MPI_INT,

i, 0,

MPI_COMM_WORLD);

MPI_Send(&a[index],

elements_left,

MPI_INT, i, 0,

MPI_COMM_WORLD);

}

// master process add its own sub array

int sum = 0;

for (i = 0; i < elements_per_process; i++)

sum += a[i];

// collects partial sums from other processes

int tmp;

for (i = 1; i < np; i++) {

MPI_Recv(&tmp, 1, MPI_INT,

MPI_ANY_SOURCE, 0,

MPI_COMM_WORLD,

&status);

int sender = status.MPI_SOURCE;

sum += tmp;

}

// prints the final sum of array

printf("Sum of array is : %d\n", sum);

}

// slave processes

else {

MPI_Recv(&n_elements_recieved,

1, MPI_INT, 0, 0,

MPI_COMM_WORLD,

&status);

// stores the received array segment

// in local array a2

MPI_Recv(&a2, n_elements_recieved,

MPI_INT, 0, 0,

MPI_COMM_WORLD,

&status);

// calculates its partial sum

int partial_sum = 0;

for (int i = 0; i < n_elements_recieved; i++)

partial_sum += a2[i];

// sends the partial sum to the root process

MPI_Send(&partial_sum, 1, MPI_INT,

0, 0, MPI_COMM_WORLD);

}

// cleans up all MPI state before exit of process

MPI_Finalize();

return 0;

}

 Slot-II

ii. Write an MPI program to find the min and max number from randomly generated 1000 numbers (stored in array) on a cluster (Hint: Use MPI_Reduce)

Solution:-

#include <mpi.h>

#include <stdio.h>

#include <stdlib.h>

#include <time.h>

#include <limits.h>

#define ARRAY_SIZE 1000

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

    int my_rank, num_processes;

    int* array;

    int local_min = INT_MAX, global_min;

    int i;

    MPI_Init(&argc, &argv);

    MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);

    MPI_Comm_size(MPI_COMM_WORLD, &num_processes);

    srand(time(NULL) + my_rank);

    array = (int*) malloc(ARRAY_SIZE / num_processes * sizeof(int));

    for (i = 0; i < ARRAY_SIZE / num_processes; i++) {

        array[i] = rand() % 1000;

        if (array[i] < local_min) {

            local_min = array[i];

        }

    }

    MPI_Reduce(&local_min, &global_min, 1, MPI_INT, MPI_MIN, 0, MPI_COMM_WORLD);

    if (my_rank == 0) {

        printf("The minimum number is %d\n", global_min);

    }

    free(array);

    MPI_Finalize();

    return 0;

}