RandomGenerator.hpp

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#ifndef RANDOM_GENERATOR_DEFINED
#define RANDOM_GENERATOR_DEFINED
 
#include <cstdint>
 
namespace sisi4s {
class RandomGenerator {
public:
  RandomGenerator(unsigned int seed = 1, int shaking = 32)
      : x(seed ^ 521288629)
      , y(seed ^ 362436069)
      , z(seed ^ 16163801)
      , n(seed ^ 1131199209)
      , c(y > x) {
    for (int i(0); i < shaking; ++i) nextInteger();
  }
 
  double nextUniform() {
    uint64_t i(nextCoarseInteger() >> 20);
    for (int j(1); j < 6; ++j) {
      i <<= 8;
      i |= nextCoarseInteger() >> 24;
    }
    return static_cast<double>(i) / static_cast<double>(1l << 52);
  }
 
  unsigned int nextInteger() {
    unsigned int i(nextCoarseInteger() >> 24);
    // draw 4 random numbers using 8 of their most significant bits
    for (int j(1); j < 4; ++j) {
      i <<= 8;
      i |= nextCoarseInteger() >> 24;
    }
    return i;
  }
 
  unsigned int nextCoarseInteger() {
    unsigned int s;
    if (y - c > x) {
      s = y - c - x;
      c = 0;
    } else {
      s = y - c - x - 18;
      c = 1;
    }
    x = y;
    y = z;
    z = s;
    n = 69069 * n + 1013904243;
    return s + n;
  }
 
protected:
  unsigned int x, y, z, n, c;
};
} // namespace sisi4s
 
#endif