4. Write a OpenMP program to find the prime numbers from 1 to n employing parallel for directive. Record both serial and parallel execution times.
COMMAND:
- Create:
gedit prg4.c - Compile:
gcc -fopenmp prg4.c -o prg4-lm - Run:
export OMP_NUM_THREADS=4 && ./prg4
PROGRAM:
#include <stdio.h>
#include <math.h>
#include <omp.h>
int is_prime(int num) {
if (num < 2) return 0;
for (int i = 2; i <= sqrt(num); i++) {
if (num % i == 0)
return 0;
}
return 1;
}
int main() {
int n;
printf("Enter the value of n: ");
scanf("%d", &n);
printf("\nPrime numbers from 1 to %d:\n", n);
for (int i = 1; i <= n; i++) {
if (is_prime(i))
printf("%d ", i);
}
printf("\n");
double start_time, end_time;
start_time = omp_get_wtime();
for (int i = 1; i <= n; i++) {
is_prime(i);
}
end_time = omp_get_wtime();
printf("Serial Time: %f seconds\n", end_time - start_time);
start_time = omp_get_wtime();
#pragma omp parallel for
for (int i = 1; i <= n; i++) {
is_prime(i);
}
end_time = omp_get_wtime();
printf("Parallel Time: %f seconds\n", end_time - start_time);
return 0;
}OUTPUT:
