emily
4c29ec126d
dont you dare criticise my code uwu just some boredom project where i tried to make a prime number finder algorithm that is as efficient as possible
115 lines
2.3 KiB
C++
115 lines
2.3 KiB
C++
// primes.cpp : This file contains the 'main' function. Program execution begins and ends there.
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//
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#include <iostream>
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#include <cmath>
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#include <string>
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#include <vector>
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#include <chrono>
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using namespace std;
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using namespace std::chrono;
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//unsigned long long origI = 3;
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//unsigned long long n = 100000000;
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unsigned int origI = 3;
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unsigned int n = 100000;
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vector<unsigned int> vprimes {2};
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milliseconds ms1 = duration_cast<milliseconds>(
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system_clock::now().time_since_epoch()
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);
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int main()
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{
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/*
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unsigned int count = 0;
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bool isprime;
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for (auto i=origI; i <= n; ++i) {
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//if ((int)pow(2, (i - 1)) % i != 1) continue;
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isprime = true;
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if (i % 2 == 0) isprime = false;
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for (int o = 3; o <= sqrt(i); o+=2) {
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if (i % o == 0) isprime = false;
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}
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if (isprime) {
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//cout << i << endl;
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++count;
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}
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}
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*/
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unsigned int count = 0;
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bool isprime;
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for (auto i = 3; i <= sqrt(n); ++i) {
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//if ((int)pow(2, (i - 1)) % i != 1) continue;
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isprime = true;
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if (i % 2 == 0) { isprime = false; continue; };
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for (auto p : vprimes) {
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if (p <= sqrt(i)) {
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if (i % p == 0) isprime = false;
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}
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else {
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break;
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}
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}
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if (isprime) {
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//cout << i << " added to fix" << endl;
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vprimes.push_back(i);
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}
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}
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for (auto i = origI; i <= n; ++i) {
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//if ((int)pow(2, (i - 1)) % i != 1) continue;
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isprime = true;
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if (i % 2 == 0) { isprime = false;continue; };
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for (auto p : vprimes) {
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if (p <= sqrt(i)) {
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if (i % p == 0) {
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isprime = false;
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break;
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}
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}
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else {
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break;
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}
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}
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if (isprime) {
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//cout << i << endl;
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++count;
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vprimes.push_back(i);
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}
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}
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milliseconds ms2 = duration_cast<milliseconds>(
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system_clock::now().time_since_epoch()
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);
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//cout << endl << endl << "There are " << count << " prime numbers between " << origI << " and " << n << endl << "The whole operation took about " << (long)ms2.count() - (long)ms1.count() << "ms to complete";
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cout << endl << endl << "There are " << count << " prime numbers between " << origI << " and " << n << endl << "The whole operation took about " << (long)ms2.count() - (long)ms1.count() << "ms to complete";
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/*
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vector:
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3 - 1'000'000 : 12784ms
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3 - 2'000'000 : 25227ms
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3 - 5'000'000 : 58557ms
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just loops:
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3 - 1'000'000 : 15135ms
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3 - 2'000'000 : 32723ms
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3 - 5'000'000 : 84439ms
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*/
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}
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