cpp/src/job_profile.cpp

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

#include <cmath>
#include <algorithm>
#include <stdexcept>

#include "job_profile.hpp"

namespace datasketches {

std::unordered_map<std::string, std::unique_ptr<job_profile>> job_profile::registry;

void job_profile::add(const char* name, std::unique_ptr<job_profile> profile) {
   registry[name] = std::move(profile);
}

job_profile& job_profile::instance(const char* name) {
  auto profile = registry.find(name);
  if (profile == registry.end()) throw std::invalid_argument("profile not found");
   return *profile->second;
}

/*
 * Computes the next larger integer point in the power series
 * <i>point = 2<sup>( i / ppo )</sup></i> given the current point in the series.
 * For illustration, this can be used in a loop as follows:
 *
 * <pre>{@code
 *     int maxP = 1024;
 *     int minP = 1;
 *     int ppo = 2;
 *
 *     for (int p = minP; p <= maxP; p = pwr2LawNext(ppo, p)) {
 *       System.out.print(p + " ");
 *     }
 *     //generates the following series:
 *     //1 2 3 4 6 8 11 16 23 32 45 64 91 128 181 256 362 512 724 1024
 * }</pre>
 *
 * param ppo Points-Per-Octave, or the number of points per integer powers of 2 in the series.
 * param curPoint the current point of the series. Must be &ge; 1.
 * returns the next point in the power series.
 */
size_t job_profile::pwr_2_law_next(size_t ppo, size_t cur_point) {
  const size_t cur = (cur_point < 1) ? 1 : cur_point;
  size_t gi = round(log2(cur) * ppo); //current generating index
  size_t next;
  do {
    next = round(pow(2.0, static_cast<double>(++gi) / ppo));
  } while (next <= cur_point);
  return next;
}

/*
 * Counts the actual number of plotting points between lgStart and lgEnd assuming the given PPO.
 * This is not a simple linear function due to points that may be skipped in the low range.
 * param lgStart Log2 of the starting value
 * param lgEnd Log2 of the ending value
 * param ppo the number of logarithmically evenly spaced points per octave.
 * returns the actual number of plotting points between lgStart and lgEnd.
 */
size_t job_profile::count_points(size_t lg_start, size_t lg_end, size_t ppo) {
  size_t p = 1ULL << lg_start;
  const size_t end = 1ULL << lg_end;
  size_t count = 0;
  while (p <= end) {
    p = pwr_2_law_next(ppo, p);
    count++;
  }
  return count;
}

size_t job_profile::get_num_trials(size_t x, size_t lg_min_x, size_t lg_max_x, size_t lg_min_trials, size_t lg_max_trials) {
  const double slope = static_cast<double>(lg_max_trials - lg_min_trials) / (static_cast<double>(lg_min_x) - static_cast<double>(lg_max_x));
  const double lg_trials = slope * (log2(x) - lg_min_x) + lg_max_trials;
  return pow(2, lg_trials);
}

std::vector<std::string> job_profile::get_profile_names() {
  std::vector<std::string> names;
  for (auto& entry : registry) {
    if (entry.first.empty() || entry.first.length() == 0) { continue; }
    names.push_back(entry.first);
  }
  std::sort(names.begin(), names.end());
  return names;
}

}