C ++ obtain the running time of a process

Use the functions in the C Runtime Library, so it has platform portability.

Include header file: Time. h

# Include <time. h>

Function introduction:

1. Clock ()

Function:

Returns the time taken by the processor to call a process or function.

Function prototype:

Clock_t clock (void );

Return Value:

If the process is successful, the number of CPU tick messages returned from the execution of the process to the time when clock () is called (clock_t is a long integer) is returned)

-1 is returned if the request fails;

Note: To convert clock_t to seconds or milliseconds, divide it by clocks_per_secclk_tck or clk_tck (name earlier than 6.0)

In the time. h file, a constant clocks_per_sec is also defined to indicate the number of clock time units in a second. Its definition is as follows:

# Define clocks_per_sec (clock_t) 1000)

2. difftime ()

Function:

Returns the time interval between two time_t variables, that is, the time difference between two time points.

Function prototype:

Double difftime (time_t Timer1, Time_t
Timer0 );

Parameters:

Timer1: End Time
Timer0: Start Time

Return Value:

Double-precision floating point value

Note: Both clock_t and time_t are unsigned long values, but one represents milliseconds and the other represents seconds.

Example:

# Include <time. h> # include <stdio. h> # include <stdlib. h> void main () {time_t c_start, t_start, c_end, t_end; c_start = clock (); t_start = Time (null ); // used to pause system ("pause"); c_end = clock (); t_end = Time (null); printf ("the pause used % f ms by time (). \ n ", difftime (c_end, c_start); printf (" the pause used % f s by clock (). \ n ", difftime (t_end, t_start ));}

Output result:
The pause used 12203.000000 MS by time ().
The pause used 13.000000 s by clock ().