Function estimateClockResolution

Bcore/src/main/cpp/Dobby/tests/catch.hpp:10454–10482

}

auto estimateClockResolution() -> uint64_t {
  uint64_t sum                     = 0;
  static const uint64_t iterations = 1000000;

  auto startTime = getCurrentNanosecondsSinceEpoch();

  for (std::size_t i = 0; i < iterations; ++i) {

    uint64_t ticks;
    uint64_t baseTicks = getCurrentNanosecondsSinceEpoch();
    do {
      ticks = getCurrentNanosecondsSinceEpoch();
    } while (ticks == baseTicks);

    auto delta = ticks - baseTicks;
    sum += delta;

    // If we have been calibrating for over 3 seconds -- the clock
    // is terrible and we should move on.
    // TBD: How to signal that the measured resolution is probably wrong?
    if (ticks > startTime + 3 * nanosecondsInSecond) {
      return sum / i;
    }
  }

  // We're just taking the mean, here. To do better we could take the std. dev and exclude outliers
  // - and potentially do more iterations if there's a high variance.
  return sum / iterations;
}
auto getEstimatedClockResolution() -> uint64_t {
  static auto s_resolution = estimateClockResolution();
  return s_resolution;