Horrible RNG but probably better than mersenne twister.cpp

  inline uint64_t xorshf96()
  {
    static thread_local uint64_t x = 123456789, y = 362436069, z = 521288629;
    x ^= x << 16;
    x ^= x >> 5;
    x ^= x << 1;

    const uint64_t t = x;
    x = y;
    y = z;
    z = t ^ x ^ y;

    return z;
  }

  inline uint64_t xorshf96(uint64_t& x, uint64_t& y, uint64_t& z)
  {
    x ^= x << 16;
    x ^= x >> 5;
    x ^= x << 1;

    const uint64_t t = x;
    x = y;
    y = z;
    z = t ^ x ^ y;

    return z;
  }

  inline double rng()
  {
    uint64_t bits = 1023ull << 52ull | xorshf96() & 0xfffffffffffffull;
    double dst;
    memcpy(&dst, &bits, sizeof(double));
    return dst - 1.0;
  }

  template<typename T, typename Q>
  T map(T val, Q r1s, Q r1e, Q r2s, Q r2e)
  {
    return (val - r1s) / (r1e - r1s) * (r2e - r2s) + r2s;
  }

  inline double rng(double low, double high)
  {
    return map(rng(), 0.0, 1.0, low, high);
  }

  // generator
  class RNG
  {
  public:
    RNG()
    {
      void* val = this;
      memcpy(&x, &val, sizeof(uint64_t));
    }

    RNG(uint64_t s) : x(s) {}

    double Get()
    {
      uint64_t bits = 1023ull << 52ull | xorshf96(x, y, z) & 0xfffffffffffffull;
      double dst;
      memcpy(&dst, &bits, sizeof(double));
      return dst - 1.0;
    }

    double Get(double low, double high)
    {
      return map(Get(), 0.0, 1.0, low, high);
    }

  private:
    uint64_t x{};
    uint64_t y{ 362436069 };
    uint64_t z{ 521288629 };
  };

  inline thread_local RNG random;