On Tue, Nov 18, 2008 at 7:56 PM, Howard Hinnant <hinnant@twcny.rr.com> wrote:
It seems a shame that process_clock does not really meet the proposed standard clock requirements (its now() doesn't return the time_point). That being said, I can see why you didn't. This clock really has 3 distinct "time points" and one needs to set each of those three with one system call.
Yep, and I couldn't see any practical downside to the proposed now() signature. Other than that, I did try to make process_clock conform.
If one wanted, one could easily create a user_time_clock wrapper around processor_clock to adapt it to the standard clock requirements if needed.
Yes. Interesting. That hadn't occurred to me.
Just for general education purposes, here's a portable processor-time clock (just to show how easy it is to build a custom clock):
#include <ctime> #include <cstdio> #include <chrono>
class processor_clock { public: typedef std::clock_t rep; typedef std::ratio<1, CLOCKS_PER_SEC> period; typedef std::chrono::duration<rep, period> duration; typedef std::chrono::time_point<processor_clock> time_point; static const bool is_monotonic = true;
static time_point now() {return time_point(duration(std::clock()));} };
int main() { processor_clock::time_point t1 = processor_clock::now(); processor_clock::time_point t2 = processor_clock::now(); std::printf("%g seconds\n", std::chrono::duration<double>(t2-t1).count()); }
Output:
4e-06 seconds
I'll add that to the docs. The clock requirements are really nice; they are totally minimalist, yet provide all the functionality needed. Did you look at the boost/chrono/timer.hpp header? It supplies a timer template to create a timer from any clock. I'd be curious to get your reactionsl Thanks, --Beman