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Class event

boost::compute::event — An event corresponding to an operation on a compute device.

Synopsis

// In header: <boost/compute/event.hpp>


class event {
public:
  // construct/copy/destruct
  event();
  explicit event(cl_event, bool = true);
  event(const event &);
  event(event &&) noexcept;
  event & operator=(const event &);
  event & operator=(event &&) noexcept;
  ~event();

  // public member functions
  cl_event & get() const;
  cl_int status() const;
  cl_command_type get_command_type() const;
  template<typename T> T get_info(cl_event_info) const;
  template<int Enum> unspecified get_info() const;
  template<typename T> T get_profiling_info(cl_profiling_info) const;
  void wait();
  void set_callback(void(BOOST_COMPUTE_CL_CALLBACK *callback)(cl_event event, cl_int status, void *user_data), 
                    cl_int = CL_COMPLETE, void * = 0);
  template<typename Function> 
    void set_callback(Function, cl_int = CL_COMPLETE);
  template<typename Duration> 
    Duration duration(cl_profiling_info = CL_PROFILING_COMMAND_START, 
                      cl_profiling_info = CL_PROFILING_COMMAND_END) const;
  bool operator==(const event &) const;
  bool operator!=(const event &) const;
};

Description

Event objects are used to track operations running on the device (such as kernel executions and memory transfers). Event objects are returned by the various enqueue_* methods of the command_queue class.

Events can be used to synchronize operations between the host and the device. The wait() method will block execution on the host until the operation corresponding to the event on the device has completed. The status of the operation can also be polled with the status() method.

Event objects can also be used for performance profiling. In order to use events for profiling, the command queue must be constructed with the CL_QUEUE_PROFILING_ENABLE flag. Then the duration() method can be used to retrieve the total duration of the operation on the device:

std::cout << "time = " << e.duration<std::chrono::milliseconds>().count() << "ms\n";

See Also:

future<T>, wait_list

event public construct/copy/destruct

  1. event();
    Creates a null event object.
  2. explicit event(cl_event event, bool retain = true);
  3. event(const event & other);
    Makes a new event as a copy of other.
  4. event(event && other) noexcept;
    Move-constructs a new event object from other.
  5. event & operator=(const event & other);
    Copies the event object from other to *this.
  6. event & operator=(event && other) noexcept;
    Move-assigns the event from other to *this.
  7. ~event();
    Destroys the event object.

event public member functions

  1. cl_event & get() const;
    Returns a reference to the underlying OpenCL event object.
  2. cl_int status() const;
    Returns the status of the event.
  3. cl_command_type get_command_type() const;
    Returns the command type for the event.
  4. template<typename T> T get_info(cl_event_info info) const;

    Returns information about the event.

    See the documentation for clGetEventInfo() for more information.

  5. template<int Enum> unspecified get_info() const;

    This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

  6. template<typename T> T get_profiling_info(cl_profiling_info info) const;

    Returns profiling information for the event.

    See Also:

    event::duration()

    See the documentation for clGetEventProfilingInfo() for more information.

  7. void wait();

    Blocks until the actions corresponding to the event have completed.

  8. void set_callback(void(BOOST_COMPUTE_CL_CALLBACK *callback)(cl_event event, cl_int status, void *user_data), 
                      cl_int status = CL_COMPLETE, void * user_data = 0);

    Registers a function to be called when the event status changes to status (by default CL_COMPLETE). The callback is passed the OpenCL event object, the event status, and a pointer to arbitrary user data.

    See the documentation for clSetEventCallback() for more information.

    [Warning] Warning

    This method is only available if the OpenCL version is 1.1 or later.

  9. template<typename Function> 
      void set_callback(Function callback, cl_int status = CL_COMPLETE);

    Registers a generic function to be called when the event status changes to status (by default CL_COMPLETE).

    The function specified by callback must be invokable with zero arguments (e.g. callback()).

    [Warning] Warning

    This method is only available if the OpenCL version is 1.1 or later.

  10. template<typename Duration> 
      Duration duration(cl_profiling_info start = CL_PROFILING_COMMAND_START, 
                        cl_profiling_info end = CL_PROFILING_COMMAND_END) const;

    Returns the total duration of the event from start to end.

    For example, to print the number of milliseconds the event took to execute:

    std::cout << event.duration<std::chrono::milliseconds>().count() << " ms" << std::endl;
    

    See Also:

    event::get_profiling_info()

  11. bool operator==(const event & other) const;
    Returns true if the event is the same as other.
  12. bool operator!=(const event & other) const;
    Returns true if the event is different from other.

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