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  1. #include <sys/time.h>
  2. #include <stdio.h>
  3.  
  4. double getdoubletime() {
  5.     struct timeval t;
  6.     gettimeofday(&t, NULL);
  7.     return (double) t.tv_sec + ((double) t.tv_usec * 1e-6);
  8. }
  9.  
  10. #include <math.h>
  11. #include <stdlib.h>
  12.  
  13. #define N 65536
  14.  
  15. int main(int argc, char const *argv[]) {
  16.     size_t i;
  17.     double t0;
  18.     // generate some random floating-point numbers
  19.     double numbers[N];
  20.     double fractionals[N];
  21.     for (i=0; i<N; ++i) {
  22.         numbers[i] = rand() + rand() / (double)RAND_MAX;
  23.     }
  24.     // extract fractional part: method 1
  25.     t0 = getdoubletime();
  26.     for (i=0; i<N; ++i) {
  27.         fractionals[i] = remainder(numbers[i], 1.0);
  28.     }
  29.     printf("method 1 took %lf seconds (using remainder)\n", getdoubletime() - t0);
  30.     // extract fractional part: method 2
  31.     t0 = getdoubletime();
  32.     for (i=0; i<N; ++i) {
  33.         fractionals[i] = numbers[i] - (long)numbers[i];
  34.     }
  35.     printf("method 2 took %lf seconds (casting to long)\n", getdoubletime() - t0);
  36.     // extract fractional part: method 3
  37.     t0 = getdoubletime();
  38.     for (i=0; i<N; ++i) {
  39.         fractionals[i] = numbers[i] - floor(numbers[i]);
  40.     }
  41.     printf("method 3 took %lf seconds (using floor)\n", getdoubletime() - t0);
  42.     // extract fractional part: method 4
  43.     t0 = getdoubletime();
  44.     double integral;
  45.     for (i=0; i<N; ++i) {
  46.         fractionals[i] = modf(numbers[i], &integral);
  47.     }
  48.     printf("method 4 took %lf seconds (using modf)\n", getdoubletime() - t0);
  49.     // extract fractional part: method 5
  50.     t0 = getdoubletime();
  51.     for (i=0; i<N; ++i) {
  52.         fractionals[i] = fmod(numbers[i], 1.0);
  53.     }
  54.     printf("method 5 took %lf seconds (using fmod)\n", getdoubletime() - t0);
  55.  
  56.     return 0;
  57. }
  58.  
Success #stdin #stdout 0.01s 2544KB
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stdin
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Standard input is empty
stdout
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method 1 took 0.003156 seconds (using remainder)
method 2 took 0.000000 seconds (casting to long)
method 3 took 0.000001 seconds (using floor)
method 4 took 0.001966 seconds (using modf)
method 5 took 0.003049 seconds (using fmod)
https://ideone.com/Jxe14E
language:
C (gcc 8.3)
created:
7 years ago
visibility:
public

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