ThreadPoolTest.h

// Mantid Repository : https://github.com/mantidproject/mantid
//
// Copyright © 2018 ISIS Rutherford Appleton Laboratory UKRI,
//   NScD Oak Ridge National Laboratory, European Spallation Source,
//   Institut Laue - Langevin & CSNS, Institute of High Energy Physics, CAS
// SPDX - License - Identifier: GPL - 3.0 +
#pragma once

#include <cxxtest/TestSuite.h>

#include "MantidKernel/FunctionTask.h"
#include "MantidKernel/ProgressBase.h"
#include "MantidKernel/ThreadPool.h"
#include "MantidKernel/ThreadScheduler.h"
#include "MantidKernel/ThreadSchedulerMutexes.h"
#include "MantidKernel/Timer.h"

#include <Poco/Thread.h>

#include <cstdlib>
#include <memory>

using namespace Mantid::Kernel;

//=======================================================================================

class TimeWaster {
public:
  static size_t waste_time(double seconds) {
    // Waste time, but use up the CPU!
    std::size_t num = 0;
    Mantid::Kernel::Timer time;
    while (time.elapsed(false) < seconds) {
      double x = 1.1;
      for (int j = 0; j < 100000; j++) {
        x = x * x;
        x = x + x;
        x = x / 1.1;
      }
      num += 1;
    }
    return num;
  }

  void waste_time_with_lock(double seconds) {
    {
      std::lock_guard<std::mutex> lock(m_mutex);
      std::cout << "waste_time for " << seconds << " seconds.\n";
    }
    waste_time(seconds);
  }

  /** Add a number but use a lock to avoid contention */
  void add_to_number(size_t adding) {
    {
      std::lock_guard<std::mutex> lock(m_mutex);
      total += adding;
    }
  }

private:
  std::mutex m_mutex;

public:
  size_t total;
};

//=======================================================================================

int threadpooltest_check = 0;

void threadpooltest_function() { threadpooltest_check = 12; }

std::vector<int> threadpooltest_vec;
void threadpooltest_adding_stuff(int val) {
  // TODO: Mutex
  threadpooltest_vec.emplace_back(val);
}

// Counter for the test.
size_t TaskThatAddsTasks_counter;
std::mutex TaskThatAddsTasks_mutex;

//=======================================================================================
/** Class that adds tasks to its scheduler */
class TaskThatAddsTasks : public Task {
public:
  // ctor
  TaskThatAddsTasks(ThreadScheduler *scheduler, size_t depth) : Task(), m_scheduler(scheduler), depth(depth) {
    // Use a randomized cost function; this will have an effect on the sorted
    // schedulers.
    m_cost = rand();
  }

  // Run the task
  void run() override {
    if (depth < 4) {
      // Add ten tasks (one level deeper)
      for (size_t i = 0; i < 10; i++) {
        m_scheduler->push(std::make_shared<TaskThatAddsTasks>(m_scheduler, depth + 1));
      }
    } else {
      // Lock to ensure you don't step on yourself.
      std::lock_guard<std::mutex> lock(TaskThatAddsTasks_mutex);
      // Increment the counter only at the lowest level.
      TaskThatAddsTasks_counter += 1;
    }
  }

private:
  ThreadScheduler *m_scheduler;
  size_t depth;
};

int ThreadPoolTest_TaskThatThrows_counter = 0;

//=======================================================================================
class ThreadPoolTest : public CxxTest::TestSuite {
public:
  /** Make it waste time, 0 to 16 seconds
   * DISABLED because it is (intentionally) slow. */
  void xtest_Scheduler_LargestCostFirst_wastetime() {
    ThreadPool p(new ThreadSchedulerFIFO(), 0);
    threadpooltest_vec.clear();
    TS_ASSERT_EQUALS(threadpooltest_vec.size(), 0);
    TimeWaster mywaster;

    for (int i = 0; i < 16; i++) {
      double cost = i; // time is exactly i
      // Bind to a member function of mywaster
      p.schedule(std::make_shared<FunctionTask>(std::bind(&TimeWaster::waste_time_with_lock, &mywaster, i), cost));
    }

    Timer overall;

    TS_ASSERT_THROWS_NOTHING(p.joinAll());

    std::cout << overall.elapsed() << " secs total.\n";
  }

  void test_Constructor() { ThreadPool p; }

  void test_schedule() {
    ThreadPool p;
    TS_ASSERT_EQUALS(threadpooltest_check, 0);
    p.schedule(std::make_shared<FunctionTask>(threadpooltest_function));
    TS_ASSERT_EQUALS(threadpooltest_check, 0);
    TS_ASSERT_THROWS_NOTHING(p.joinAll());
    TS_ASSERT_EQUALS(threadpooltest_check, 12);
  }

  //=======================================================================================
  //=======================================================================================
  /** Class for debugging progress reporting */
  class MyTestProgress : public ProgressBase {
  public:
    MyTestProgress(double start, double end, int64_t numSteps, ThreadPoolTest *myParent)
        : ProgressBase(start, end, numSteps), parent(myParent) {}

    void doReport(const std::string &msg = "") override {
      parent->last_report_message = msg;
      parent->last_report_counter = m_i;
      double p = m_start + m_step * double(m_i - m_ifirst);
      parent->last_report_value = p;
    }

  public:
    ThreadPoolTest *parent;
  };

  /// Index that was last set at doReport
  int64_t last_report_counter;
  double last_report_value;
  std::string last_report_message;

  void test_with_progress_reporting() {
    last_report_counter = 0;
    ThreadPool p(new ThreadSchedulerFIFO(), 1, new MyTestProgress(0.0, 1.0, 10, this));
    for (int i = 0; i < 10; i++) {
      double cost = i;
      p.schedule(std::make_shared<FunctionTask>(threadpooltest_function, cost));
    }
    TS_ASSERT_THROWS_NOTHING(p.joinAll());
    // The test reporter was called
    TS_ASSERT_EQUALS(last_report_counter, 10);
  }

  //=======================================================================================

  /** Start a threadpool before adding tasks
   * DISABLED because the timing issues make it somewhat unreliable under heavy
   * loads. */
  void xtest_start_and_wait() {
    ThreadPool p; // Makes a default scheduler
    threadpooltest_check = 0;

    // Start and allow it to wait for 1 second
    p.start(1.0);

    // Simulate doing some work
    Poco::Thread::sleep(40);

    // Now you add the task
    p.schedule(std::make_shared<FunctionTask>(threadpooltest_function));

    // Simulate doing more work (this allows the task to run)
    Poco::Thread::sleep(40);

    // The task ran before we called joinAll(). Magic!
    TS_ASSERT_EQUALS(threadpooltest_check, 12);

    // Reset and try again. The threads are still waiting, it has been less than
    // 1 second.
    threadpooltest_check = 0;
    p.schedule(std::make_shared<FunctionTask>(threadpooltest_function));
    Poco::Thread::sleep(40);
    TS_ASSERT_EQUALS(threadpooltest_check, 12);

    // You still need to call joinAll() to clean up everything.
    p.joinAll();

    // Ok, the task did execute.
    TS_ASSERT_EQUALS(threadpooltest_check, 12);
  }

  /** Start a threadpool before adding tasks. But the wait time was too short!
   * DISABLED because the timing issues make it somewhat unreliable under heavy
   * loads. */
  void xtest_start_and_wait_short_wait_time() {
    ThreadPool p; // Makes a default scheduler
    threadpooltest_check = 0;

    // Start and allow it to wait for a very short time
    p.start(0.03);

    // But it takes too long before the task is actually added
    Poco::Thread::sleep(100);
    p.schedule(std::make_shared<FunctionTask>(threadpooltest_function));
    Poco::Thread::sleep(30);
    // So the task has not run, since the threads exited before!
    TS_ASSERT_EQUALS(threadpooltest_check, 0);

    // But you can still call joinAll() to run the task that is waiting.
    p.joinAll();
    // Ok, the task did execute.
    TS_ASSERT_EQUALS(threadpooltest_check, 12);
  }

  //=======================================================================================

  /** We schedule a task, run the threads, but don't abort them.
   * Then we re-schedule stuff, and re-join.
   */
  void test_schedule_resume_tasks() {
    ThreadPool p; // Makes a default scheduler
    threadpooltest_check = 0;
    p.schedule(std::make_shared<FunctionTask>(threadpooltest_function));
    TS_ASSERT_THROWS_NOTHING(p.joinAll());
    // Ok, the task did execute.
    TS_ASSERT_EQUALS(threadpooltest_check, 12);

    // Now we reset.
    threadpooltest_check = 0;
    p.schedule(std::make_shared<FunctionTask>(threadpooltest_function));
    TS_ASSERT_THROWS_NOTHING(p.joinAll());
    TS_ASSERT_EQUALS(threadpooltest_check, 12);
  }

  void test_Scheduler_FIFO() {
    // Only use one core, it'll make things simpler
    ThreadPool p(new ThreadSchedulerFIFO(), 1);

    TS_ASSERT_EQUALS(threadpooltest_vec.size(), 0);
    for (int i = 0; i < 10; i++) {
      double cost = i;
      p.schedule(std::make_shared<FunctionTask>(std::bind(threadpooltest_adding_stuff, i), cost));
    }
    TS_ASSERT_THROWS_NOTHING(p.joinAll());
    TS_ASSERT_EQUALS(threadpooltest_vec.size(), 10);
    if (threadpooltest_vec.size() < 10)
      return;
    // The first ones added are the first ones run.
    TS_ASSERT_EQUALS(threadpooltest_vec[0], 0);
    TS_ASSERT_EQUALS(threadpooltest_vec[1], 1);
    TS_ASSERT_EQUALS(threadpooltest_vec[2], 2);
  }

  void test_Scheduler_LIFO() {
    ThreadPool p(new ThreadSchedulerLIFO(), 1);
    threadpooltest_vec.clear();
    TS_ASSERT_EQUALS(threadpooltest_vec.size(), 0);
    for (int i = 0; i < 10; i++) {
      double cost = i;
      p.schedule(std::make_shared<FunctionTask>(std::bind(threadpooltest_adding_stuff, i), cost));
    }
    TS_ASSERT_THROWS_NOTHING(p.joinAll());
    TS_ASSERT_EQUALS(threadpooltest_vec.size(), 10);
    // The last ones added are the first ones run.
    TS_ASSERT_EQUALS(threadpooltest_vec[0], 9);
    TS_ASSERT_EQUALS(threadpooltest_vec[1], 8);
    TS_ASSERT_EQUALS(threadpooltest_vec[2], 7);
  }

  void test_Scheduler_LargestCostFirst() {
    // Only use one core, it'll make things simpler
    ThreadPool p(new ThreadSchedulerLargestCost(), 1);
    threadpooltest_vec.clear();
    TS_ASSERT_EQUALS(threadpooltest_vec.size(), 0);
    for (int i = 0; i < 10; i++) {
      double cost = i;
      p.schedule(std::make_shared<FunctionTask>(std::bind(threadpooltest_adding_stuff, i), cost));
    }
    TS_ASSERT_THROWS_NOTHING(p.joinAll());
    TS_ASSERT_EQUALS(threadpooltest_vec.size(), 10);
    // The first ones added are the first ones run.
    TS_ASSERT_EQUALS(threadpooltest_vec[0], 9);
    TS_ASSERT_EQUALS(threadpooltest_vec[1], 8);
    TS_ASSERT_EQUALS(threadpooltest_vec[2], 7);
  }

  //--------------------------------------------------------------------
  /** Perform a stress test on the given scheduler.
   * This runs a large number of super-short tasks; enough that the
   * queue locking is tested against simultaneous access. A segfault
   * results if the queue is improperly accessed.
   */
  void do_StressTest_scheduler(ThreadScheduler *sched) {
    ThreadPool p(sched, 0);
    TimeWaster mywaster;
    size_t num = 30000;
    mywaster.total = 0;
    std::shared_ptr<std::mutex> lastMutex;
    for (size_t i = 0; i <= num; i++) {
      auto task =
          std::make_shared<FunctionTask>(std::bind(&TimeWaster::add_to_number, &mywaster, i), static_cast<double>(i));
      // Create a new mutex every 1000 tasks. This is more relevant to the
      // ThreadSchedulerMutexes; others ignore it.
      if (i % 1000 == 0)
        lastMutex = std::make_shared<std::mutex>();
      task->setMutex(lastMutex);
      p.schedule(task);
    }

    Timer overall;
    TS_ASSERT_THROWS_NOTHING(p.joinAll());
    // std::cout << overall.elapsed() << " secs total.\n";

    // Expected total
    size_t expected = (num * num + num) / 2;
    TS_ASSERT_EQUALS(mywaster.total, expected);
  }

  void test_StressTest_ThreadSchedulerFIFO() { do_StressTest_scheduler(new ThreadSchedulerFIFO()); }

  void test_StressTest_ThreadSchedulerLIFO() { do_StressTest_scheduler(new ThreadSchedulerLIFO()); }

  void test_StressTest_ThreadSchedulerLargestCost() { do_StressTest_scheduler(new ThreadSchedulerLargestCost()); }

  void test_StressTest_ThreadSchedulerMutexes() { do_StressTest_scheduler(new ThreadSchedulerMutexes()); }

  //--------------------------------------------------------------------
  /** Perform a stress test on the given scheduler.
   * This one creates tasks that create new tasks; e.g. 10 tasks each add
   * 10 tasks, and so on (up to a certain depth).
   * So it tests against possible segfaults of one task
   * accessing the queue while another thread is popping it.
   */
  void do_StressTest_TasksThatCreateTasks(ThreadScheduler *sched) {
    ThreadPool *p = new ThreadPool(sched, 0);
    // Create the first task, depth 0, that will recursively create 10000
    auto task = std::make_shared<TaskThatAddsTasks>(sched, 0);
    p->schedule(task);

    // Reset the total
    TaskThatAddsTasks_counter = 0;
    TS_ASSERT_THROWS_NOTHING(p->joinAll());

    // Expected total = the number of lowest level entries
    TS_ASSERT_EQUALS(TaskThatAddsTasks_counter, 10000);
    delete p;
  }

  void test_StressTest_TasksThatCreateTasks_ThreadSchedulerFIFO() {
    do_StressTest_TasksThatCreateTasks(new ThreadSchedulerFIFO());
  }

  void test_StressTest_TasksThatCreateTasks_ThreadSchedulerLIFO() {
    do_StressTest_TasksThatCreateTasks(new ThreadSchedulerLIFO());
  }

  void test_StressTest_TasksThatCreateTasks_ThreadSchedulerLargestCost() {
    do_StressTest_TasksThatCreateTasks(new ThreadSchedulerLargestCost());
  }

  void test_StressTest_TasksThatCreateTasks_ThreadSchedulerMutexes() {
    do_StressTest_TasksThatCreateTasks(new ThreadSchedulerMutexes());
  }

  //=======================================================================================
  /** Task that throws an exception */
  class TaskThatThrows : public Task {
    void run() override {
      ThreadPoolTest_TaskThatThrows_counter++;
      throw Mantid::Kernel::Exception::NotImplementedError("Test exception from TaskThatThrows.");
    }
  };

  //--------------------------------------------------------------------
  void test_TaskThatThrows() {
    ThreadPool p(new ThreadSchedulerFIFO(), 1); // one core
    ThreadPoolTest_TaskThatThrows_counter = 0;
    for (int i = 0; i < 10; i++) {
      p.schedule(std::make_shared<TaskThatThrows>());
    }
    // joinAll rethrows
    TS_ASSERT_THROWS(p.joinAll(), const std::runtime_error &);
    // And only one of the tasks actually ran (since we're on one core)
    TS_ASSERT_EQUALS(ThreadPoolTest_TaskThatThrows_counter, 1);
  }
};