What is performance-wise the best way to generate random bools?

Question

I need to generate random Boolean values on a performance-critical path.

The code which I wrote for this is

std::random_device   rd;
std::uniform_int         


        

Answer 1

Some quick benchmarks (code):

   647921509 RandomizerXorshiftPlus
   821202158 BoolGenerator2 (reusing the same buffer)
  1065582517 modified Randomizer
  1130958451 BoolGenerator2 (creating a new buffer as needed)
  1140139042 xorshift128plus
  2738780431 xorshift1024star
  4629217068 std::mt19937
  6613608092 rand()
  8606805191 std::bernoulli_distribution
 11454538279 BoolGenerator
 19288820587 std::uniform_int_distribution

For those who want ready-to-use code, I present XorShift128PlusBitShifterPseudoRandomBooleanGenerator, a tweaked version of RandomizerXorshiftPlus from the above link. On my machine, it is about as fast as @SergeRogatch's solution, but consistently about 10-20% faster when the loop count is high (≳100,000), and up to ~30% slower with smaller loop counts.

class XorShift128PlusBitShifterPseudoRandomBooleanGenerator {
public:
  bool randBool() {
    if (counter == 0) {
      counter = sizeof(GeneratorType::result_type) * CHAR_BIT;
      random_integer = generator();
    }
    return (random_integer >> --counter) & 1;
  }

private:
  class XorShift128Plus {
  public:
    using result_type = uint64_t;

    XorShift128Plus() {
      std::random_device rd;
      state[0] = rd();
      state[1] = rd();
    }

    result_type operator()() {
      auto x = state[0];
      auto y = state[1];
      state[0] = y;
      x ^= x << 23;
      state[1] = x ^ y ^ (x >> 17) ^ (y >> 26);
      return state[1] + y;
    }

  private:
    result_type state[2];
  };

  using GeneratorType = XorShift128Plus;

  GeneratorType generator;
  GeneratorType::result_type random_integer;
  int counter = 0;
};