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  1. #include <stdio.h>
  2. #include <pthread.h>
  3. #include <time.h>
  4.  
  5. #define NUM_THREADS 4
  6. #define ITERATIONS 1000000
  7.  
  8. typedef struct {
  9.     long value;
  10.     char padding[64]; // avoid false sharing
  11. } counter_t;
  12.  
  13. counter_t counters[NUM_THREADS];
  14.  
  15. void* increment(void* arg) {
  16.     int id = *(int*)arg;
  17.     for (int i = 0; i < ITERATIONS; i++) {
  18.         counters[id].value++;
  19.     }
  20.     return NULL;
  21. }
  22.  
  23. int main() {
  24.     pthread_t threads[NUM_THREADS];
  25.     int ids[NUM_THREADS];
  26.  
  27.     clock_t start = clock();
  28.  
  29.     for (int i = 0; i < NUM_THREADS; i++) {
  30.         ids[i] = i;
  31.         pthread_create(&threads[i], NULL, increment, &ids[i]);
  32.     }
  33.  
  34.     for (int i = 0; i < NUM_THREADS; i++) {
  35.         pthread_join(threads[i], NULL);
  36.     }
  37.  
  38.     clock_t end = clock();
  39.  
  40.     printf("Time (optimized): %f seconds\n",
  41.            (double)(end - start) / CLOCKS_PER_SEC);
  42.  
  43.     return 0;
  44. }
Success #stdin #stdout 0s 5292KB
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Standard input is empty
stdout
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Time (optimized): 0.000519 seconds
https://ideone.com/UDwytE
language:
C (gcc 8.3)
created:
2 hours ago
visibility:
public

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