uniform_random_number.cc

#include <functional>
#include <random>
#include <vector>

#include "test_framework/generic_test.h"
#include "test_framework/random_sequence_checker.h"
#include "test_framework/timed_executor.h"

using std::bind;
using std::default_random_engine;
using std::random_device;
using std::uniform_int_distribution;
using std::vector;

int ZeroOneRandom() {
  default_random_engine gen((random_device())());
  uniform_int_distribution<int> dis(0, 1);
  return dis(gen);
}

int UniformRandom(int lower_bound, int upper_bound) {
  int number_of_outcomes = upper_bound - lower_bound + 1, result;
  do {
    result = 0;
    for (int i = 0; (1 << i) < number_of_outcomes; ++i) {
      // ZeroOneRandom() is the provided random number generator.
      result = (result << 1) | ZeroOneRandom();
    }
  } while (result >= number_of_outcomes);
  return result + lower_bound;
}

bool UniformRandomRunner(TimedExecutor& executor, int lower_bound,
                         int upper_bound) {
  using namespace test_framework;
  vector<int> result;
  executor.Run([&] {
    std::generate_n(back_inserter(result), 100000,
                    std::bind(UniformRandom, lower_bound, upper_bound));
  });

  vector<int> sequence;
  std::transform(begin(result), end(result), back_inserter(sequence),
                 [lower_bound](int result) { return result - lower_bound; });
  return CheckSequenceIsUniformlyRandom(result, upper_bound - lower_bound + 1,
                                        0.01);
}

void UniformRandomWrapper(TimedExecutor& executor, int lower_bound,
                          int upper_bound) {
  RunFuncWithRetries(
      bind(UniformRandomRunner, std::ref(executor), lower_bound, upper_bound));
}

int main(int argc, char* argv[]) {
  std::vector<std::string> args{argv + 1, argv + argc};
  std::vector<std::string> param_names{"executor", "lower_bound",
                                       "upper_bound"};
  return GenericTestMain(args, "uniform_random_number.cc",
                         "uniform_random_number.tsv", &UniformRandomWrapper,
                         DefaultComparator{}, param_names);
}