task.h

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/* SPDX-FileCopyrightText: 2011-2022 Blender Foundation
 *
 * SPDX-License-Identifier: Apache-2.0 */
 
#pragma once
 
#include "util/list.h"
#include "util/string.h"
#include "util/tbb.h"
#include "util/thread.h"
#include "util/unique_ptr.h"
 
CCL_NAMESPACE_BEGIN
 
class TaskPool;
class TaskScheduler;
 
using TaskRunFunction = std::function<void()>;
 
/* Task Pool
 *
 * Pool of tasks that will be executed by the central TaskScheduler. For each
 * pool, we can wait for all tasks to be done, or cancel them before they are
 * done.
 *
 * TaskRunFunction may be created with std::bind or lambda expressions. */
 
class TaskPool {
 public:
  struct Summary {
    /* Time spent to handle all tasks. */
    double time_total;
 
    /* Number of all tasks handled by this pool. */
    int num_tasks_handled;
 
    /* A full multi-line description of the state of the pool after
     * all work is done.
     */
    string full_report() const;
  };
 
  TaskPool();
  ~TaskPool();
 
  void push(TaskRunFunction &&task);
 
  void wait_work(Summary *stats = nullptr); /* work and wait until all tasks are done */
  void cancel(); /* cancel all tasks and wait until they are no longer executing */
 
  static bool canceled(); /* For worker threads, test if current task pool canceled. */
 
 protected:
  tbb::task_group tbb_group;
 
  /* ** Statistics ** */
 
  /* Time stamp of first task pushed. */
  double start_time;
 
  /* Number of all tasks pushed to the pool. Cleared after wait_work() and cancel(). */
  int num_tasks_pushed;
};

class TaskScheduler {
 public:
  static void init(const int num_threads = 0);
  static void exit();
  static void free_memory();
 
  /* Maximum number of threads that will work on task. Use as little as
   * possible and leave scheduling and splitting up tasks to the scheduler. */
  static int max_concurrency();
 
 protected:
  static thread_mutex mutex;
  static int users;
  static int active_num_threads;
 
#ifdef WITH_TBB_GLOBAL_CONTROL
  static unique_ptr<tbb::global_control> global_control;
#endif
};
 
/* Dedicated Task Pool
 *
 * Like a TaskPool, but will launch one dedicated thread to execute all tasks.
 *
 * The run callback can be a lambda without arguments. */
 
class DedicatedTaskPool {
 public:
  DedicatedTaskPool();
  ~DedicatedTaskPool();
 
  void push(TaskRunFunction &&run, bool front = false);
 
  void wait();   /* wait until all tasks are done */
  void cancel(); /* cancel all tasks, keep worker thread running */
 
  bool canceled(); /* for worker thread, test if canceled */
 
 protected:
  void num_decrease(const int done);
  void num_increase();
 
  void thread_run();
  bool thread_wait_pop(TaskRunFunction &task);
 
  void clear();
 
  thread_mutex num_mutex;
  thread_condition_variable num_cond;
 
  list<TaskRunFunction> queue;
  thread_mutex queue_mutex;
  thread_condition_variable queue_cond;
 
  int num;
  bool do_cancel;
  bool do_exit;
 
  unique_ptr<thread> worker_thread;
};
 
CCL_NAMESPACE_END