googlebenchmark/src/benchmark_runner.cc

// Copyright 2015 Google Inc. All rights reserved.
//
// Licensed 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 "benchmark_runner.h"
#include "benchmark/benchmark.h"
#include "benchmark_api_internal.h"
#include "internal_macros.h"

#ifndef BENCHMARK_OS_WINDOWS
#ifndef BENCHMARK_OS_FUCHSIA
#include <sys/resource.h>
#endif
#include <sys/time.h>
#include <unistd.h>
#endif

#include <algorithm>
#include <atomic>
#include <condition_variable>
#include <cstdio>
#include <cstdlib>
#include <fstream>
#include <iostream>
#include <memory>
#include <string>
#include <thread>
#include <utility>

#include "check.h"
#include "colorprint.h"
#include "commandlineflags.h"
#include "complexity.h"
#include "counter.h"
#include "internal_macros.h"
#include "log.h"
#include "mutex.h"
#include "re.h"
#include "statistics.h"
#include "string_util.h"
#include "thread_manager.h"
#include "thread_timer.h"

namespace benchmark {

namespace internal {

MemoryManager* memory_manager = nullptr;

namespace {

static constexpr IterationCount kMaxIterations = 1000000000;

BenchmarkReporter::Run CreateRunReport(
    const benchmark::internal::BenchmarkInstance& b,
    const internal::ThreadManager::Result& results,
    IterationCount memory_iterations,
    const MemoryManager::Result& memory_result, double seconds,
    int64_t repetition_index) {
  // Create report about this benchmark run.
  BenchmarkReporter::Run report;

  report.run_name = b.name;
  report.error_occurred = results.has_error_;
  report.error_message = results.error_message_;
  report.report_label = results.report_label_;
  // This is the total iterations across all threads.
  report.iterations = results.iterations;
  report.time_unit = b.time_unit;
  report.threads = b.threads;
  report.repetition_index = repetition_index;
  report.repetitions = b.repetitions;

  if (!report.error_occurred) {
    if (b.use_manual_time) {
      report.real_accumulated_time = results.manual_time_used;
    } else {
      report.real_accumulated_time = results.real_time_used;
    }
    report.cpu_accumulated_time = results.cpu_time_used;
    report.complexity_n = results.complexity_n;
    report.complexity = b.complexity;
    report.complexity_lambda = b.complexity_lambda;
    report.statistics = b.statistics;
    report.counters = results.counters;

    if (memory_iterations > 0) {
      report.has_memory_result = true;
      report.allocs_per_iter =
          memory_iterations ? static_cast<double>(memory_result.num_allocs) /
                                  memory_iterations
                            : 0;
      report.max_bytes_used = memory_result.max_bytes_used;
    }

    internal::Finish(&report.counters, results.iterations, seconds, b.threads);
  }
  return report;
}

// Execute one thread of benchmark b for the specified number of iterations.
// Adds the stats collected for the thread into *total.
void RunInThread(const BenchmarkInstance* b, IterationCount iters,
                 int thread_id, ThreadManager* manager) {
  internal::ThreadTimer timer(
      b->measure_process_cpu_time
          ? internal::ThreadTimer::CreateProcessCpuTime()
          : internal::ThreadTimer::Create());
  State st = b->Run(iters, thread_id, &timer, manager);
  CHECK(st.iterations() >= st.max_iterations)
      << "Benchmark returned before State::KeepRunning() returned false!";
  {
    MutexLock l(manager->GetBenchmarkMutex());
    internal::ThreadManager::Result& results = manager->results;
    results.iterations += st.iterations();
    results.cpu_time_used += timer.cpu_time_used();
    results.real_time_used += timer.real_time_used();
    results.manual_time_used += timer.manual_time_used();
    results.complexity_n += st.complexity_length_n();
    internal::Increment(&results.counters, st.counters);
  }
  manager->NotifyThreadComplete();
}

class BenchmarkRunner {
 public:
  BenchmarkRunner(const benchmark::internal::BenchmarkInstance& b_,
                  std::vector<BenchmarkReporter::Run>* complexity_reports_)
      : b(b_),
        complexity_reports(*complexity_reports_),
        min_time(!IsZero(b.min_time) ? b.min_time : FLAGS_benchmark_min_time),
        repeats(b.repetitions != 0 ? b.repetitions
                                   : FLAGS_benchmark_repetitions),
        has_explicit_iteration_count(b.iterations != 0),
        pool(b.threads - 1),
        iters(has_explicit_iteration_count ? b.iterations : 1) {
    run_results.display_report_aggregates_only =
        (FLAGS_benchmark_report_aggregates_only ||
         FLAGS_benchmark_display_aggregates_only);
    run_results.file_report_aggregates_only =
        FLAGS_benchmark_report_aggregates_only;
    if (b.aggregation_report_mode != internal::ARM_Unspecified) {
      run_results.display_report_aggregates_only =
          (b.aggregation_report_mode &
           internal::ARM_DisplayReportAggregatesOnly);
      run_results.file_report_aggregates_only =
          (b.aggregation_report_mode & internal::ARM_FileReportAggregatesOnly);
    }

    for (int repetition_num = 0; repetition_num < repeats; repetition_num++) {
      DoOneRepetition(repetition_num);
    }

    // Calculate additional statistics
    run_results.aggregates_only = ComputeStats(run_results.non_aggregates);

    // Maybe calculate complexity report
    if ((b.complexity != oNone) && b.last_benchmark_instance) {
      auto additional_run_stats = ComputeBigO(complexity_reports);
      run_results.aggregates_only.insert(run_results.aggregates_only.end(),
                                         additional_run_stats.begin(),
                                         additional_run_stats.end());
      complexity_reports.clear();
    }
  }

  RunResults&& get_results() { return std::move(run_results); }

 private:
  RunResults run_results;

  const benchmark::internal::BenchmarkInstance& b;
  std::vector<BenchmarkReporter::Run>& complexity_reports;

  const double min_time;
  const int repeats;
  const bool has_explicit_iteration_count;

  std::vector<std::thread> pool;

  IterationCount iters;  // preserved between repetitions!
  // So only the first repetition has to find/calculate it,
  // the other repetitions will just use that precomputed iteration count.

  struct IterationResults {
    internal::ThreadManager::Result results;
    IterationCount iters;
    double seconds;
  };
  IterationResults DoNIterations() {
    VLOG(2) << "Running " << b.name.str() << " for " << iters << "\n";

    std::unique_ptr<internal::ThreadManager> manager;
    manager.reset(new internal::ThreadManager(b.threads));

    // Run all but one thread in separate threads
    for (std::size_t ti = 0; ti < pool.size(); ++ti) {
      pool[ti] = std::thread(&RunInThread, &b, iters, static_cast<int>(ti + 1),
                             manager.get());
    }
    // And run one thread here directly.
    // (If we were asked to run just one thread, we don't create new threads.)
    // Yes, we need to do this here *after* we start the separate threads.
    RunInThread(&b, iters, 0, manager.get());

    // The main thread has finished. Now let's wait for the other threads.
    manager->WaitForAllThreads();
    for (std::thread& thread : pool) thread.join();

    IterationResults i;
    // Acquire the measurements/counters from the manager, UNDER THE LOCK!
    {
      MutexLock l(manager->GetBenchmarkMutex());
      i.results = manager->results;
    }

    // And get rid of the manager.
    manager.reset();

    // Adjust real/manual time stats since they were reported per thread.
    i.results.real_time_used /= b.threads;
    i.results.manual_time_used /= b.threads;
    // If we were measuring whole-process CPU usage, adjust the CPU time too.
    if (b.measure_process_cpu_time) i.results.cpu_time_used /= b.threads;

    VLOG(2) << "Ran in " << i.results.cpu_time_used << "/"
            << i.results.real_time_used << "\n";

    // So for how long were we running?
    i.iters = iters;
    // Base decisions off of real time if requested by this benchmark.
    i.seconds = i.results.cpu_time_used;
    if (b.use_manual_time) {
      i.seconds = i.results.manual_time_used;
    } else if (b.use_real_time) {
      i.seconds = i.results.real_time_used;
    }

    return i;
  }

  IterationCount PredictNumItersNeeded(const IterationResults& i) const {
    // See how much iterations should be increased by.
    // Note: Avoid division by zero with max(seconds, 1ns).
    double multiplier = min_time * 1.4 / std::max(i.seconds, 1e-9);
    // If our last run was at least 10% of FLAGS_benchmark_min_time then we
    // use the multiplier directly.
    // Otherwise we use at most 10 times expansion.
    // NOTE: When the last run was at least 10% of the min time the max
    // expansion should be 14x.
    bool is_significant = (i.seconds / min_time) > 0.1;
    multiplier = is_significant ? multiplier : std::min(10.0, multiplier);
    if (multiplier <= 1.0) multiplier = 2.0;

    // So what seems to be the sufficiently-large iteration count? Round up.
    const IterationCount max_next_iters =
        0.5 + std::max(multiplier * i.iters, i.iters + 1.0);
    // But we do have *some* sanity limits though..
    const IterationCount next_iters = std::min(max_next_iters, kMaxIterations);

    VLOG(3) << "Next iters: " << next_iters << ", " << multiplier << "\n";
    return next_iters;  // round up before conversion to integer.
  }

  bool ShouldReportIterationResults(const IterationResults& i) const {
    // Determine if this run should be reported;
    // Either it has run for a sufficient amount of time
    // or because an error was reported.
    return i.results.has_error_ ||
           i.iters >= kMaxIterations ||  // Too many iterations already.
           i.seconds >= min_time ||      // The elapsed time is large enough.
           // CPU time is specified but the elapsed real time greatly exceeds
           // the minimum time.
           // Note that user provided timers are except from this sanity check.
           ((i.results.real_time_used >= 5 * min_time) && !b.use_manual_time);
  }

  void DoOneRepetition(int64_t repetition_index) {
    const bool is_the_first_repetition = repetition_index == 0;
    IterationResults i;

    // We *may* be gradually increasing the length (iteration count)
    // of the benchmark until we decide the results are significant.
    // And once we do, we report those last results and exit.
    // Please do note that the if there are repetitions, the iteration count
    // is *only* calculated for the *first* repetition, and other repetitions
    // simply use that precomputed iteration count.
    for (;;) {
      i = DoNIterations();

      // Do we consider the results to be significant?
      // If we are doing repetitions, and the first repetition was already done,
      // it has calculated the correct iteration time, so we have run that very
      // iteration count just now. No need to calculate anything. Just report.
      // Else, the normal rules apply.
      const bool results_are_significant = !is_the_first_repetition ||
                                           has_explicit_iteration_count ||
                                           ShouldReportIterationResults(i);

      if (results_are_significant) break;  // Good, let's report them!

      // Nope, bad iteration. Let's re-estimate the hopefully-sufficient
      // iteration count, and run the benchmark again...

      iters = PredictNumItersNeeded(i);
      assert(iters > i.iters &&
             "if we did more iterations than we want to do the next time, "
             "then we should have accepted the current iteration run.");
    }

    // Oh, one last thing, we need to also produce the 'memory measurements'..
    MemoryManager::Result memory_result;
    IterationCount memory_iterations = 0;
    if (memory_manager != nullptr) {
      // Only run a few iterations to reduce the impact of one-time
      // allocations in benchmarks that are not properly managed.
      memory_iterations = std::min<IterationCount>(16, iters);
      memory_manager->Start();
      std::unique_ptr<internal::ThreadManager> manager;
      manager.reset(new internal::ThreadManager(1));
      RunInThread(&b, memory_iterations, 0, manager.get());
      manager->WaitForAllThreads();
      manager.reset();

      memory_manager->Stop(&memory_result);
    }

    // Ok, now actualy report.
    BenchmarkReporter::Run report =
        CreateRunReport(b, i.results, memory_iterations, memory_result,
                        i.seconds, repetition_index);

    if (!report.error_occurred && b.complexity != oNone)
      complexity_reports.push_back(report);

    run_results.non_aggregates.push_back(report);
  }
};

}  // end namespace

RunResults RunBenchmark(
    const benchmark::internal::BenchmarkInstance& b,
    std::vector<BenchmarkReporter::Run>* complexity_reports) {
  internal::BenchmarkRunner r(b, complexity_reports);
  return r.get_results();
}

}  // end namespace internal

}  // end namespace benchmark