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Compare the runtime of the sieve against vectors and bool arrays
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#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; | |
} |
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