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  1. #include <iostream>
  2. #include <cmath>
  3. #include <vector>
  4. #include <omp.h>
  5.  
  6. using namespace std;
  7.  
  8. bool isPrime(int n) {
  9.     if (n <= 1) 
  10.         return false;
  11.     if (n == 2) 
  12.         return true;
  13.     if (n % 2 == 0) 
  14.         return false;
  15.  
  16.     for (int i = 3; i <= sqrt(n); i += 2) {
  17.         if (n % i == 0) return false;
  18.     }
  19.     return true;
  20. }
  21.  
  22. int main() {
  23.     int numProcs, size;
  24.     cout << "Num Processes: ";
  25.     cin >> numProcs;
  26.     cout << "Size: ";
  27.     cin >> size;
  28.  
  29.     vector<bool> primes((size - 2) / 2 + 1, false); // The total number of prime numbers in the primes array, as it is only odd numbers starting from 3
  30.  
  31. #pragma omp parallel for schedule(dynamic) num_threads(numProcs)
  32.     for (int i = 3; i <= size; i += 2) {
  33.         if (isPrime(i)) {
  34.             primes[(i - 3) / 2] = true;
  35.         }
  36.     }
  37.  
  38.     cout << "Prime numbers up to " << size << ":\n";
  39.     cout << 2 << " "; // Since 2 is the only even prime number
  40.     for (int i = 0; i < primes.size(); i++) {
  41.         if (primes[i]) {
  42.             cout << i * 2 + 3 << " ";
  43.         }
  44.     }
  45.     cout << endl;
  46.  
  47.     return 0;
  48. }
Success #stdin #stdout 0.01s 5300KB
comments (?)
stdin
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4 25
stdout
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Num Processes: Size: Prime numbers up to 25:
2 3 5 7 11 13 17 19 23
https://ideone.com/2naLFu
language:
C++ (gcc 8.3)
created:
13 days ago
visibility:
public

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