Vicente J. Botet Escriba wrote:
* Why does stop returns cpu-times? Why by reference? Why elapsed is not returned by reference?
cpu_times elapsed() const noexcept;
const cpu_times& stop() noexcept;
The interface is, of course, directed by the current implementation. Still, it would be appropriate for stop() to return by value to avoid forcing the implementation to store a cpu_times instance in the timer.
* I would associate the operations pairwise start/stop and suspend/resume. I guess it would be easier to explain the semantics.
Yes. Of course. I knew I didn't quite like the current semantics, but it just didn't click. Another advantage of start/stop and suspend/resume is that RAII classes can be used to control the timer. Here's the new interface: void start(); void stop(); bool is_stopped(); void suspend(); void resume(); bool is_suspended(); cpu_times elapsed(); start() notes the current time as the start time and marks the timer as not stopped, if is_stopped(), and marks the timer as not suspended. stop() notes the current time as the end time and marks the timer as stopped, if !is_stopped(), and marks the timer as not suspended. suspend() notes the current time as the suspension time and marks the object as being suspended, if !is_stopped() && !is_suspended(). resume() calls start() and arranges for a future call to elapsed() to include the time elapsed until suspend() was called plus the time that elapses subsequently, if is_suspended(). Reasonable? I know that means that both start and end times must be stored with this interface (two cpu_times instances, for example), but that seems a worthwhile price. Here's a use case addressed by these ideas: nanosecond_type status_time(0); cpu_timer timer; for (int i(0); i < 100; ++i) { task_to_time(); scoped_suspender _(timer); nanosecond_type const current_time(timer.elapsed().user); if (1000000000 < current_time - status_time) { report(timer); status_time = current_time; } } scoped_suspender is an RAII class that calls suspend() and resume(). Thus, the overhead of checking the elapsed time and writing output is not included in the time tracked by the timer. This approach permits doing non-timed work of various sorts in the midst of timed work. scoped_suspender might be a class template with a generator: auto _(make_scoped_suspender(timer)); That would allow supporting any timer type that provides suspend() and resume(). I suspect that this use case would be pretty common, so it could be captured: timer_reporter report(1000000000); // once per second cpu_timer timer; for (int i(0); i < 100; ++i) { task_to_time(); report(timer); } void timer_reporter::operator ()(cpu_timer & _timer) { if (_timer.is_stopped()) { return; } scoped_suspender _(_timer); nanosecond_type const current(_timer.elapsed().user); if (delay_ < current - last_) { std::string const formatted( _timer.format(precision_, format_)); os_ << formatted; last_ = current; } } Obviously, I'm suggesting that timer_reporter is somewhat similar to auto_cpu_timer in that it would save a std::ostream & for output, as well as the precision and a format string for calling cpu_timer::format(). I purposely did not supply the timer as a constructor argument because that would require construction after a timer already started or else stopping the timer, constructing the timer_reporter, and then starting the timer. _____ Rob Stewart robert.stewart@sig.com Software Engineer using std::disclaimer; Dev Tools & Components Susquehanna International Group, LLP http://www.sig.com ________________________________ IMPORTANT: The information contained in this email and/or its attachments is confidential. If you are not the intended recipient, please notify the sender immediately by reply and immediately delete this message and all its attachments. Any review, use, reproduction, disclosure or dissemination of this message or any attachment by an unintended recipient is strictly prohibited. Neither this message nor any attachment is intended as or should be construed as an offer, solicitation or recommendation to buy or sell any security or other financial instrument. Neither the sender, his or her employer nor any of their respective affiliates makes any warranties as to the completeness or accuracy of any of the information contained herein or that this message or any of its attachments is free of viruses.