RSS Feed
Download our iPhone app
Browse DevX
Sign up for e-mail newsletters from DevX

By submitting your information, you agree that devx.com may send you DevX offers via email, phone and text message, as well as email offers about other products and services that DevX believes may be of interest to you. DevX will process your information in accordance with the Quinstreet Privacy Policy.


Using High-resolution Timers : Page 2

For multimedia streaming, games, and profiling, Standard C++'s time-meausurement facilities are limited. For high-resolution timers, look to the POSIX libraries




Building the Right Environment to Support AI, Machine Learning and Deep Learning

Time and time() Again
Applications that need a high-resolution time measurement can use the quasi-portable gettimeofday() function defined by the POSIX standard and also available on most versions of Windows. gettimeofday() is declared in the <sys/time.h> header:

int gettimeofday (struct timeval *tp, void*);

It writes to tp the number of seconds that have elapsed since the epoch, i.e., 01/01/1970 00:00:00. Unlike time(), which uses a one-second granularity, gettimeofday() expresses the current timestamp in seconds and microseconds (millionths of a second) since the epoch. As with may other time-measuring functions, the actual resolution of gettimeofday() depends on the underlying hardware of your machine, so you shouldn't assume that every platform supporting gettimeofday() will necessarily have a microsecond granularity.

gettimeofday() writes the current timestamp into a timeval data structure:

struct timeval { time_t tv_sec; //seconds suseconds_t tv_usec; //microseconds };

The following code listing obtains the current timestamp using gettimeofday() and displays it onscreen:

#include <sys/time.h> #include <iostream> int main() { struct timeval tv; gettimeofday(&tv,0); std::cout<<"the current timestamp is: " <<tv.tv_sec<<"."<<tv.tv_usec<<std::endl; }

A granularity of one millionth of a second sounds impressive, yet some applications require even higher. Timers with a resolution of a nanosecond are now available on real-time POSIX systems.

Comment and Contribute






(Maximum characters: 1200). You have 1200 characters left.



Thanks for your registration, follow us on our social networks to keep up-to-date