Compare the runtime of the sieve against vectors and bool arrays

sieve-eratosthenes-runtime-comparison.cpp

#include <iostream>
#include <vector>
#include <cstring>

using namespace std;

bool* boolPrimeSieveMemset(int64_t size) {
	bool* prime = new bool[size + 1];
	memset(prime, true, size + 1);				//faster than loops and vectors
	prime[0] = false;
	prime[1] = false;
	for (int64_t p = 2; p*p <= size; p++) {
		if (prime[p] == true) {
			for (int64_t i = p * 2; i <= size; i += p) {
				prime[i] = false;
			}
		}
	}
	return prime;
}

bool* boolPrimeSieveLoops(int64_t size) {
	bool* prime = new bool[size + 1];
	for(int i = 0; i <= size; ++i){
		prime[i] = true;
	}
	prime[0] = false;
	prime[1] = false;
	for (int64_t p = 2; p*p <= size; p++) {
		if (prime[p] == true) {
			for (int64_t i = p * 2; i <= size; i += p) {
				prime[i] = false;
			}
		}
	}
	return prime;
}

vector<bool> vectorPrimeSieve(int64_t size){
	vector<bool> prime(size+1);
	for(int i = 0; i <= size; ++i){
		prime[i] = true;
	}
	prime[0] = false;
	prime[1] = false;
	for (int64_t p = 2; p*p <= size; p++) {
		if (prime[p] == true) {
			for (int64_t i = p * 2; i <= size; i += p) {
				prime[i] = false;
			}
		}
	}
	return prime;
}

int main(){
	int size;
	cout << "Enter the size: ";
	cin >> size;

	clock_t start = clock();
	bool* a = boolPrimeSieveMemset(size);
	clock_t end = clock();
	double time = (double)(end - start) / CLOCKS_PER_SEC * 1000.0;
	cout << "Memset: " << time << " ms" << endl;
	delete[] a;

	start = clock();
	bool* b = boolPrimeSieveLoops(size);
	end = clock();
	time = (double)(end - start) / CLOCKS_PER_SEC * 1000.0;
	cout << "Loops: " << time << " ms" << endl;
	delete[] b;

	start = clock();
	vector<bool> c = vectorPrimeSieve(size);
	end = clock();
	time = (double)(end - start) / CLOCKS_PER_SEC * 1000.0;
	cout << "Vector: " << time << " ms" << endl;

  return 0;
}