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  1. #include <iostream>
  2.  
  3. //This function returns the same result for given values but should be somewhat random.
  4. double PRH(unsigned iterations, int x, int y) {
  5.         unsigned long long hash;
  6.         x &= 0xFFF;
  7.         y &= 0xFFF;
  8.         iterations &= 0xFF;
  9.         hash = (iterations << 24);
  10.         hash |= (y << 12);
  11.         hash |= x;
  12.         unsigned long long rem = hash & 3;
  13.         unsigned long long h = hash;
  14.  
  15.         switch (rem) {
  16.             case 3:
  17.                 hash += h;
  18.                 hash ^= hash << 32;
  19.                 hash ^= h << 36;
  20.                 hash += hash >> 22;
  21.                 break;
  22.             case 2:
  23.                 hash += h;
  24.                 hash ^= hash << 22;
  25.                 hash += hash >> 34;
  26.                 break;
  27.             case 1:
  28.                 hash += h;
  29.                 hash ^= hash << 20;
  30.                 hash += hash >> 2;
  31.         }
  32.         hash ^= hash << 6;
  33.         hash += hash >> 10;
  34.         hash ^= hash << 8;
  35.         hash += hash >> 34;
  36.         hash ^= hash << 50;
  37.         hash += hash >> 12;
  38.  
  39.         return (hash & 0xFFFF) / static_cast<double>(0xFFFF);
  40.     }
  41.  
  42. int main()
  43. {
  44.     std::cout << PRH(25, 6, 7);
  45. }
Success #stdin #stdout 0s 3296KB
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0.17406
https://ideone.com/Ldbp9i
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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