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  1. #include <stdio.h>
  2. #include <stdint.h>
  3. #include <string.h>
  4. #include <assert.h>
  5.  
  6. float make_float(uint32_t random23)
  7. {
  8.     uint32_t pattern = 0x3f800000;
  9.  
  10.     random23 &= 0x7fffff;
  11.     pattern |= random23;
  12.  
  13.     assert(sizeof(float) == sizeof(uint32_t));
  14.     char buffer[sizeof(float)];
  15.     memcpy(buffer, &pattern, sizeof(float));
  16.     float f;
  17.     memcpy(&f, buffer, sizeof(float));
  18.  
  19.     return f - 1.0;
  20. }
  21.  
  22. float make_float2(uint32_t random23)
  23. {
  24.     random23 &= 0x7fffff;
  25.     return (float)random23 / (1 << 23);
  26. }
  27.  
  28. int main(void) {
  29.     for (uint32_t i = 0; (i >> 23) < 1; i++) {
  30.         float a = make_float(i), b = make_float2(i);
  31.         if (a != b) {
  32.             printf("Mismatch: %d -> %.20f != %.20f!\n", i, a, b);
  33.             return 1;
  34.         }
  35.     }
  36.     printf("No mismatch found.\n");
  37.     return 0;
  38. }
  39.  
Success #stdin #stdout 0.07s 2112KB
comments (?)
stdin
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Standard input is empty
stdout
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No mismatch found.
https://ideone.com/aEH1Qa
language:
C (gcc 8.3)
created:
8 years ago
visibility:
public

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