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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <string.h>
  4. #include <time.h>
  5.  
  6. double sec(){
  7.     struct timespec t;
  8.     clock_gettime(CLOCK_MONOTONIC, &t);
  9.     return t.tv_sec + 1e-9*t.tv_nsec;
  10. }
  11.  
  12. int main(){
  13.     size_t n_bytes = 16*1000*1000*sizeof(double);
  14.     int *src_initialized   = (int*)malloc(n_bytes);
  15.     int *src_uninitialized = (int*)malloc(n_bytes);
  16.     int *dst_initialized   = (int*)malloc(n_bytes);
  17.     int *dst_uninitialized = (int*)malloc(n_bytes);
  18.  
  19.     memset(src_initialized, 0, n_bytes);
  20.  
  21.     for (int k = 0; k < 100; k++){
  22.         double t0 = sec();
  23.  
  24.         memcpy(dst_initialized, src_initialized, n_bytes);
  25.  
  26.         double t1 = sec();
  27.  
  28.         memcpy(dst_uninitialized, src_uninitialized, n_bytes);
  29.  
  30.         double t2 = sec();
  31.  
  32.         double initialized_gbps   = n_bytes*1e-9/(t1 - t0);
  33.         double uninitialized_gbps = n_bytes*1e-9/(t2 - t1);
  34.  
  35.         printf("  initialized: %f gbyte/sec\n", initialized_gbps);
  36.         printf("uninitialized: %f gbyte/sec\n", uninitialized_gbps);
  37.         printf("\n");
  38.     }
  39.  
  40.     free(src_initialized);
  41.     free(src_uninitialized);
  42.     free(dst_initialized);
  43.     free(dst_uninitialized);
  44.  
  45.     return 0;
  46. }
  47.  
  48.  
Success #stdin #stdout 1.47s 15232KB
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Standard input is empty
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https://ideone.com/LQ9m9P
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
public

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