Wtime a c function which returns a reading of the wall clock time.
Measure wall clock time in c.
Following is a sample c program where we measure time taken by fun.
Note that this function does not strictly conform to iso c which specifies net cpu time as the return value.
Using clock gettime function in c c.
End clock.
The function fun waits for enter key press to terminate.
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.
Fortunately all mpi implementations provide you with such a clock.
For parallel programming the important thing to measure is the elapsed wallclock time.
The gettimeofday function returns the wall clock time elapsed since the epoch and store it in the timevalstructure expressed as seconds and microseconds.
For that you will have to use chronometers.
Do the work.
In all multivalue basic languages you can use the time function to return the number of seconds from midnight.
The system s notion of the current greenwich time and the current time zone.
Calculating the elapsed wall clock time of a program is helpful to determine how much time it actually takes for a program to complete.
The easy method is to take the time the program ends and then subtract the time the program starts.
The openmp system provides a function used as follows.
As it turns out c has many functions available to get the current time.
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.
For example if the cpu is shared by other processes std clock time may advance slower than wall clock.
Prototype syntax.
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.
The clock function tells how much wall clock time has passed since the crt initialization during process start.
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.
Tp parameter points to a structure containing atleast the following members.
This can be found by subtracting an initial reading of the wallclock time from a final one.
To obtain cpu times use the win32 getprocesstimes function.
Cpu time used double end start clocks per sec.