PerformanceTestCore.hpp

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//                Copyright Oliver J. Rosten 2020.                //
// Distributed under the GNU GENERAL PUBLIC LICENSE, Version 3.0. //
//    (See accompanying file LICENSE.md or copy at                //
//          https://www.gnu.org/licenses/gpl-3.0.en.html)         //
 
#pragma once
 
#include "sequoia/TestFramework/RegularTestCore.hpp"
#include "sequoia/Maths/Statistics/StatisticalAlgorithms.hpp"
#include "sequoia/TestFramework/FileEditors.hpp"
 
#include <chrono>
#include <random>
#include <future>
#include <thread>
 
namespace sequoia::testing
{
  template<std::invocable Task>
  [[nodiscard]]
  std::chrono::duration<double> profile(Task task)
  {
    const timer t{};
    task();
 
    return t.time_elapsed();
  }
 
  template<test_mode Mode, std::invocable F, std::invocable S>
  bool check_relative_performance(std::string_view description, test_logger<Mode>& logger, F fast, S slow, const double minSpeedUp, const double maxSpeedUp, const std::size_t trials, const double num_sds, const std::size_t maxAttempts)
  {
    if((minSpeedUp <= 1) || (maxSpeedUp <= 1))
      throw std::logic_error{"Relative performance test requires speed-up factors > 1"};
 
    if(minSpeedUp > maxSpeedUp)
      throw std::logic_error{"maxSpeedUp must be >= minSpeedUp"};
 
    if(num_sds <=1)
      throw std::logic_error{"Number of standard deviations is required to be > 1"};
 
    if(!maxAttempts)
      throw std::logic_error{"Number of attempts is required to be > 0"};
 
    if(trials < 5)
      throw std::logic_error{"Number of trials is required to be > 4"};
 
    using namespace std::chrono;
    using namespace maths;
 
    std::string summary{};
    std::size_t remainingAttempts{maxAttempts};
    bool passed{};
 
    auto timer{
       [](auto task, std::vector<double>& timings){
         timings.push_back(profile(task).count());
       }
    };
 
    while(remainingAttempts > 0)
    {
      const auto adjustedTrials{trials*(maxAttempts - remainingAttempts + 1)};
 
      std::vector<double> fastData, slowData;
      fastData.reserve(adjustedTrials);
      slowData.reserve(adjustedTrials);
 
      std::random_device generator;
      for(std::size_t i{}; i < adjustedTrials; ++i)
      {
        std::uniform_real_distribution<double> distribution{0.0, 1.0};
        const bool fastFirst{(distribution(generator) < 0.5)};
 
        if(fastFirst)
        {
          timer(fast, fastData);
          timer(slow, slowData);
        }
        else
        {
          timer(slow, slowData);
          timer(fast, fastData);
        }
      }
 
      auto compute_stats{
        [](auto first, auto last) {
          const auto data{sample_standard_deviation(first, last)};
          return std::make_pair(data.first.value(), data.second.value());
        }
      };
 
      std::ranges::sort(fastData);
      std::ranges::sort(slowData);
 
      const auto [sig_f, m_f]{compute_stats(fastData.cbegin()+1, fastData.cend()-1)};
      const auto [sig_s, m_s]{compute_stats(slowData.cbegin()+1, slowData.cend()-1)};
 
      if(m_f + sig_f < m_s - sig_s)
      {
        if(sig_f >= sig_s)
        {
          passed =    (minSpeedUp * m_f <= (m_s + num_sds * sig_s))
                   && (maxSpeedUp * m_f >= (m_s - num_sds * sig_s));
        }
        else
        {
          passed =    (m_s / maxSpeedUp <= (m_f + num_sds * sig_f))
                   && (m_s / minSpeedUp >= (m_f - num_sds * sig_f));
        }
      }
      else
      {
        passed = false;
      }
 
      auto stats{
        [num_sds](std::string_view prefix, const auto mean, const auto sig){
 
          std::ostringstream message{};
          message << mean << "s" << " +- " << num_sds << " * " << sig << "s";
 
          return std::string{prefix}.append(" Task duration: ").append(message.str());
        }
      };
 
      auto summarizer{
        [m_f, m_s, minSpeedUp, maxSpeedUp](){
          std::ostringstream message{};
          message << " [" << m_s / m_f << "; (" << minSpeedUp << ", " << maxSpeedUp << ")]";
 
          return message.str();
        }
      };
 
      summary = append_lines(stats("Fast", m_f, sig_f), stats("Slow", m_s, sig_s)).append(summarizer());
 
      if((test_logger<Mode>::mode == test_mode::false_negative) ? !passed : passed)
      {
        break;
      }
 
      --remainingAttempts;
    }
 
    sentinel<Mode> sentry{logger, append_lines(description, summary)};
    sentry.log_performance_check();
 
    if(!passed)
    {
      sentry.log_performance_failure("");
    }
 
    return passed;
  }
 
  template<class T, class Period>
  [[nodiscard]]
  std::chrono::duration<T, Period> calibrate(std::chrono::duration<T, Period> target)
  {
    using namespace std::chrono;
 
    std::array<double, 7> timings{};
    for (auto& t : timings)
    {
      t = profile([target]() { std::this_thread::sleep_for(target); }).count();
    }
 
    std::ranges::sort(timings);
    const auto [sig_f, m_f] {maths::sample_standard_deviation(timings.cbegin() + 1, timings.cend() - 1)};
    if (sig_f && m_f)
    {
      if ((m_f.value() - sig_f.value()) > duration_cast<duration<double>>(target).count())
      {
        constexpr auto inverse{Period::den / Period::num};
        return std::chrono::duration<T, Period>{static_cast<T>(std::ceil(inverse* (m_f.value() + 5* sig_f.value())))};
      }
    }
 
    return target;
  }
 
  template<test_mode Mode>
  class performance_extender
  {
  public:
    constexpr static test_mode mode{Mode};
 
    performance_extender() = default;
 
    template<class Self, std::invocable F, std::invocable S>
    bool check_relative_performance(this Self& self, const reporter& description, F fast, S slow, const double minSpeedUp, const double maxSpeedUp, const std::size_t trials=5, const double num_sds=4)
    {
      return testing::check_relative_performance(self.report(description), self.m_Logger, fast, slow, minSpeedUp, maxSpeedUp, trials, num_sds, 3);
    }
  protected:
    ~performance_extender() = default;
 
    performance_extender(performance_extender&&)            noexcept = default;
    performance_extender& operator=(performance_extender&&) noexcept = default;
  };
 
  [[nodiscard]]
  std::string_view postprocess(std::string_view testOutput, std::string_view referenceOutput);
 
  template<test_mode Mode>
  class basic_performance_test : public basic_test<Mode, performance_extender<Mode>>
  {
  public:
    using base_type = basic_test<Mode, performance_extender<Mode>>;
    using duration  = typename base_type::duration;
 
    using base_type::base_type;
 
    [[nodiscard]]
    log_summary summarize(duration delta) const;
  protected:
    ~basic_performance_test() = default;
 
    basic_performance_test(basic_performance_test&&)            noexcept = default;
    basic_performance_test& operator=(basic_performance_test&&) noexcept = default;
  };
 
  using performance_test                = basic_performance_test<test_mode::standard>;
  using performance_false_positive_test = basic_performance_test<test_mode::false_positive>;
  using performance_false_negative_test = basic_performance_test<test_mode::false_negative>;
 
  template<concrete_test T>
    requires std::is_base_of_v<basic_performance_test<T::mode>, T>
  struct is_parallelizable<T> : std::false_type {};
}