Note that this function does not strictly conform to iso c which specifies net cpu time as the return value.
Measure wall clock time in c.
Wtime a c function which returns a reading of the wall clock time.
The system s notion of the current greenwich time and the current time zone.
Cpu time used double end start clocks per sec.
It is defined in sys time h header file and takes two arguments the first arugment is reference to the timevalstructure and the second argument is a null pointer.
Include sys time h int gettimeofday struct timeval restrict tp void restrict tzp.
The obvious one is gettimeofday.
In all multivalue basic languages you can use the time function to return the number of seconds from midnight.
For parallel programming the important thing to measure is the elapsed wallclock time.
There are a lot of ways to measure time in computer science but as a general rule of thumb you should always use a clock that measures the elapsed real time or wall time.
The clock function tells how much wall clock time has passed since the crt initialization during process start.
End clock.
The clock gettime function gets the current time of the clock specified by clock id and puts it into the buffer pointed to by tp.
For example if the cpu is shared by other processes std clock time may advance slower than wall clock.
This can be found by subtracting an initial reading of the wallclock time from a final one.
Prototype syntax.
For that you will have to use chronometers.
As it turns out c has many functions available to get the current time.
Int clock gettime clockid t clock id struct timespec tp.
Tp parameter points to a structure containing atleast the following members.
The openmp system provides a function used as follows.
Following is a sample c program where we measure time taken by fun.
The easy method is to take the time the program ends and then subtract the time the program starts.
The gettimeofday function returns the wall clock time elapsed since the epoch and store it in the timevalstructure expressed as seconds and microseconds.
Std clock time may advance faster or slower than the wall clock depending on the execution resources given to the program by the operating system.
The function fun waits for enter key press to terminate.
Using clock gettime function in c c.
Fortunately all mpi implementations provide you with such a clock.