| Taskflow: A General-purpose Task-parallel Programming System

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Public Member Functions | List of all members
tf::ObserverInterface Class Referenceabstract

class to derive an executor observer More...

`#include <taskflow/observer/interface.hpp>`

## Public Member Functions
virtual | ~ObserverInterface ()=default
| virtual destructor
virtual void | set_up (size_t num_workers)=0
| constructor-like method to call when the executor observer is fully created
virtual void | on_entry (WorkerView wv, TaskView task_view)=0
| method to call before a worker thread executes a closure
virtual void | on_exit (WorkerView wv, TaskView task_view)=0
| method to call after a worker thread executed a closure

## Detailed Description

class to derive an executor observer

The tf::ObserverInterface class allows users to define custom methods to monitor the behaviors of an executor. This is particularly useful when you want to inspect the performance of an executor and visualize when each thread participates in the execution of a task. To prevent users from direct access to the internal threads and tasks, tf::ObserverInterface provides immutable wrappers, tf::WorkerView and tf::TaskView, over workers and tasks.

Please refer to tf::WorkerView and tf::TaskView for details.

Example usage:

struct MyObserver : public tf::ObserverInterface {
MyObserver(const std::string& name) {
std::cout << "constructing observer " << name << '\n';
}
void set_up(size_t num_workers) override final {
std::cout << "setting up observer with " << num_workers << " workers\n";
}
void on_entry(WorkerView w, tf::TaskView tv) override final {
std::ostringstream oss;
oss << "worker " << w.id() << " ready to run " << tv.name() << '\n';
std::cout << oss.str();
}
void on_exit(WorkerView w, tf::TaskView tv) override final {
std::ostringstream oss;
oss << "worker " << w.id() << " finished running " << tv.name() << '\n';
std::cout << oss.str();
}
};
tf::Taskflow taskflow;
tf::Executor executor;
// insert tasks into taskflow
// ...
// create a custom observer
std::shared_ptr<MyObserver> observer = executor.make_observer<MyObserver>("MyObserver");
// run the taskflow
executor.run(taskflow).wait();
tf::Executor::run
tf::Future< void > run(Taskflow &taskflow)
runs a taskflow once
tf::Executor::make_observer
std::shared_ptr< Observer > make_observer(ArgsT &&... args)
constructs an observer to inspect the activities of worker threads
tf::ObserverInterface
class to derive an executor observer
Definition interface.hpp:81
tf::ObserverInterface::set_up
virtual void set_up(size_t num_workers)=0
constructor-like method to call when the executor observer is fully created
tf::ObserverInterface::on_entry
virtual void on_entry(WorkerView wv, TaskView task_view)=0
method to call before a worker thread executes a closure
tf::ObserverInterface::on_exit
virtual void on_exit(WorkerView wv, TaskView task_view)=0
method to call after a worker thread executed a closure
tf::TaskView
class to access task information from the observer interface
Definition task.hpp:1546

## Member Function Documentation

## ◆ on_entry()

virtual void tf::ObserverInterface::on_entry | ( | WorkerView | wv,
|  | TaskView | task_view )
| pure virtual

method to call before a worker thread executes a closure

Parameters

  wv | an immutable view of this worker thread
  task_view | a constant wrapper object to the task

## ◆ on_exit()

virtual void tf::ObserverInterface::on_exit | ( | WorkerView | wv,
|  | TaskView | task_view )
| pure virtual

method to call after a worker thread executed a closure

Parameters

  wv | an immutable view of this worker thread
  task_view | a constant wrapper object to the task

## ◆ set_up()

virtual void tf::ObserverInterface::set_up | ( | size_t | num_workers | ) |
| pure virtual

constructor-like method to call when the executor observer is fully created

Parameters

  num_workers | the number of the worker threads in the executor

The documentation for this class was generated from the following file:

- taskflow/observer/interface.hpp