double kll_merge_accuracy_profile::run_trial()

in cpp/src/kll_merge_accuracy_profile.cpp [30:58]

• 24 lines of code
• 6 McCabe index (conditional complexity)

double kll_merge_accuracy_profile::run_trial(float* values, unsigned stream_length) {
  unsigned seed = std::chrono::system_clock::now().time_since_epoch().count();
  std::shuffle(values, values + stream_length, std::default_random_engine(seed));

  const unsigned num_sketches = 8;
  std::unique_ptr<kll_sketch<float>> sketches[num_sketches];
  for (unsigned i = 0; i < num_sketches; i++) {
    sketches[i] = std::unique_ptr<kll_sketch<float>>(new kll_sketch<float>());
  }

  unsigned j = 0;
  for (size_t i = 0; i < stream_length; i++) {
    sketches[j]->update(values[i]);
    j++;
    if (j == num_sketches) j = 0;
  }

  kll_sketch<float> sketch;
  for (unsigned i = 0; i < num_sketches; i++) sketch.merge(*sketches[i]);

  double max_rank_error = 0;
  for (size_t i = 1; i <= stream_length; i++) {
    double true_rank = static_cast<double>(i) / stream_length;
    double est_rank = sketch.get_rank(i);
    max_rank_error = std::max(max_rank_error, fabs(true_rank - est_rank));
  }

  return max_rank_error;
}