framework::performance::Timer Class Reference

Time how long a specific operation takes and serialize the result with ROOT. More...

#include <Timer.h>

Public Member Functions
	Timer ()=default
	create a timer but don't start it yet
virtual	~Timer ()=default
	create defualt destructor
void	reset ()
	reset a timer to un-started state without re-allocating
void	start ()
	start the timer
void	stop ()
	stop the timer
double	duration () const
	retrieve the value of the duration in seconds
void	write (TDirectory *location, const std::string &name) const
	Write ourselves under the input name to the input location.
	ClassDef (Timer, 1)

Private Types
using	clock = std::chrono::high_resolution_clock

Private Attributes
std::chrono::time_point< clock >	begin_
	The time_point when the timer is started.
std::chrono::time_point< clock >	end_
	The time_point when the timer is stopped.
long int	start_time_ {-1}
	Time stamp for when timer was started in nanoseconds since UNIX epoch.
double	duration_ {-1}
	Length of time recorded by the timer in seconds.

Detailed Description

Time how long a specific operation takes and serialize the result with ROOT.

Under-the-hood, we use std::chrono::time_point and std::chrono::duration along with std::chrono::high_resolution_clock so we can clearly and faithfully time how long things take and transparently convert the resulting duration into seconds (including sub-second increments). Since ROOT doesn't have a dictionary for serializing these std::chrono classes (and I'm not interested in making one), I simply mark those helper-members as "transient" (have //! on the line they are declared in) so they are ignored by the dictionary generation. The fundamental members start_time_ and duration_ are what end up being written to disk.

Below is an example of reading the absolute timer from a test run of this performance logging infrastructure. As you can see, the two atomic types are available for reading but the std::chrono::time_point objects are not.

>>> import uproot
>>> with uproot.open('test_performance.root') as f:
...     f['performance/absolute'].members
...
{'start_time_': 1701704424941358702, 'duration_': 0.078910213}

Definition at line 38 of file Timer.h.

Member Typedef Documentation

clock

using framework::performance::Timer::clock = std::chrono::high_resolution_clock

private

Definition at line 39 of file Timer.h.

Member Function Documentation

duration()

double framework::performance::Timer::duration

(

)

const

retrieve the value of the duration in seconds

Definition at line 27 of file Timer.cxx.

{ return duration_; }

References duration_.

reset()

void framework::performance::Timer::reset

(

)

reset a timer to un-started state without re-allocating

Definition at line 8 of file Timer.cxx.

                  {
  begin_ = {};
  end_ = {};
  start_time_ = -1;
  duration_ = -1;
}

References begin_, duration_, end_, and start_time_.

start()

void framework::performance::Timer::start

(

)

start the timer

Definition at line 15 of file Timer.cxx.

                  {
  begin_ = clock::now();
  start_time_ = std::chrono::duration_cast<std::chrono::nanoseconds>(
                    begin_.time_since_epoch())
                    .count();
}

References begin_, and start_time_.

Referenced by framework::performance::Tracker::absoluteStart().

stop()

void framework::performance::Timer::stop

(

)

stop the timer

Definition at line 22 of file Timer.cxx.

                 {
  end_ = clock::now();
  duration_ = std::chrono::duration<double>(end_ - begin_).count();
}

References begin_, duration_, and end_.

Referenced by framework::performance::Tracker::absoluteStop().

write()

void framework::performance::Timer::write	(	TDirectory *	location,
		const std::string &	name ) const

Write ourselves under the input name to the input location.

This is just here to avoid repeating the boiler-plate

location->WriteObject(&timer_obj, name.c_str());

Since I don't like seeing & or c_str() in my code.

Definition at line 29 of file Timer.cxx.

                                                                   {
  location->WriteObject(this, name.c_str());
}

Referenced by framework::performance::Tracker::~Tracker().

Member Data Documentation

begin_

std::chrono::time_point<clock> framework::performance::Timer::begin_

private

The time_point when the timer is started.

The comment beginning with //! is what marks this member as "transient" for ROOT I/O. not serialized, just for measurement purposes

Definition at line 47 of file Timer.h.

Referenced by reset(), start(), and stop().

duration_

double framework::performance::Timer::duration_ {-1}

private

Length of time recorded by the timer in seconds.

Sub-second intervals are recorded as well (so if the timer ran for 1 millisecond you would see 0.001 stored in this member variable).

Set to -1 if timer was not ended

Definition at line 74 of file Timer.h.

{-1};

Referenced by duration(), reset(), and stop().

end_

std::chrono::time_point<clock> framework::performance::Timer::end_

private

The time_point when the timer is stopped.

The comment beginning with //! is what marks this member as "transient" for ROOT I/O. not serialized, just for measurement purposes

Definition at line 56 of file Timer.h.

Referenced by reset(), and stop().

start_time_

long int framework::performance::Timer::start_time_ {-1}

private

Time stamp for when timer was started in nanoseconds since UNIX epoch.

Set to -1 if timer was not started

Definition at line 63 of file Timer.h.

{-1};

Referenced by reset(), and start().

---

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

• Framework/include/Framework/Performance/Timer.h
• Framework/src/Framework/Performance/Timer.cxx