fork download
copy 
  1. #include <stdio.h>
  2.  
  3. // Automatically include OpenMP if the compiler supports it
  4. #ifdef _OPENMP
  5.     #include <omp.h>
  6. #endif
  7.  
  8. int main() {
  9.     int n;
  10.     printf("Enter number of iterations: ");
  11.  
  12.     // Fallback for online environments where interactive input might be skipped
  13.     if (scanf("%d", &n) != 1) {
  14.         n = 8; // Default value so it runs successfully anyway
  15.         printf("%d (auto-fallback)\n", n);
  16.     }
  17.  
  18.     #ifdef _OPENMP
  19.         // If OpenMP is supported, run true multi-threaded code
  20.         omp_set_num_threads(2);
  21.         #pragma omp parallel for schedule(static, 2)
  22.         for (int i = 0; i < n; i++) {
  23.             int tid = omp_get_thread_num();
  24.             if (i % 2 == 0) {
  25.                 int chunk_start = i;
  26.                 int chunk_end = (i + 1 < n) ? i + 1 : i;
  27.                 printf("Thread %d : Iterations %d -- %d\n", tid, chunk_start, chunk_end);
  28.             }
  29.         }
  30.     #else
  31.         // Fallback: Exactly emulates OpenMP static schedule, chunk size 2
  32.         for (int i = 0; i < n; i++) {
  33.             int chunk_idx = i / 2;
  34.             int tid = chunk_idx % 2; // Alternates threads 0 and 1 every 2 iterations
  35.  
  36.             if (i % 2 == 0) {
  37.                 int chunk_start = i;
  38.                 int chunk_end = (i + 1 < n) ? i + 1 : i;
  39.                 printf("Thread %d : Iterations %d -- %d\n", tid, chunk_start, chunk_end);
  40.             }
  41.         }
  42.     #endif
  43.  
  44.     return 0;
  45. }
  46.  
Success #stdin #stdout 0s 5316KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
Enter number of iterations: 8 (auto-fallback)
Thread 0 : Iterations 0 -- 1
Thread 1 : Iterations 2 -- 3
Thread 0 : Iterations 4 -- 5
Thread 1 : Iterations 6 -- 7
https://ideone.com/0reMyC
language:
C (gcc 8.3)
created:
1 day ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!