xorshift128+

xorshift128p.hpp

struct xorshift128p {
  uint64_t x[2];
  xorshift128p(uint64_t s1, uint64_t s2) {
    x[0] = s1;
    x[1] = s2;
  }
  xorshift128p(uint64_t s[2]) {
    x[0] = s[0];
    x[1] = s[1];
  }
  void seed(uint64_t s1, uint64_t s2) {
    x[0] = s1;
    x[1] = s2;
  }
  void seed(uint64_t s[2]) {
    x[0] = s[0];
    x[1] = s[1];
  }
  uint64_t rand_int(void)
  {   
    uint64_t t = this->x[0];
    uint64_t const s = this->x[1];
    this->x[0] = s;
    t ^= t << 23;		// a
    t ^= t >> 18;		// b -- Again, the shifts and the multipliers are tunable
    t ^= s ^ (s >> 5);	// c
    this->x[1] = t;
    return t + s;
  }
};