I've written an algorithm that has the following goal: finding all prime numbers up to a specified integer. I've made two different algorithms actually: on one hand, I've used the concept beyond the ancient sieve of eratosthenes; on the other, I've used a function called isprime() that tests if a number is prime. For instance, let's say I want to determine wich method is faster. So I need to time a piece of code in each algorithm.(adsbygoogle = window.adsbygoogle || []).push({});

As an example, here's the code of the first algorithm:

I've omitted the isprime() function definition, because I felt it's unnecessary. The problem with this approach is that my computer writes the numbers so rapidly that I probably will need to write the time in milliseconds if I wanted the algorithm to write every prime number up to a small number, as 11. Is there a function that allows me to do that?Code (Text):#include <stdio.h>

#include <math.h>

#include <time.h>

int isprime(int num);

int main () {

int n, num;

time_t t1, t2;

printf("Enter a number\n");

while (scanf("%d", &n) != 1) {

printf("Error: Try again.\n");

while (getchar() != '\n')

;

}

printf("Prime numbers\n");

time(&t1);

for (num = 2; num <= n; num += 1) {

if (isprime(num) == 1)

printf("%d\n", num);

}

time(&t2);

printf("Time elapsed: %f ms\n", (float)(t2-t1));

return 0;

}

Thank you on advance.

Links I've consulted

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# [C] time.h

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