The Stopwatch package provides ways to measure intervals of program execution time. The package consists of a single class, Stopwatch . Typically, you use this class during the performance-tuning phase of program development.

Stopwatch class

Provides the means to measure intervals of time between specified program events.

Header

#include <stopwatch.hxx>

Alternative Header

#include <Stopwatch.h>

Declaration

class Stopwatch { public: Stopwatch(); void start(); void stop(); void reset(); int status() const; double system() const; double user() const; double real() const; static double resolution(); };

Description

Objects of this class measure program execution time and return the result in floating-point seconds. The class includes the start , stop , and reset functions familiar to users of a mechanical stopwatch.

You can time the entire program or select certain portions of the program to time; for example, a specified loop or program module. You can create a different Stopwatch object for each independent program activity, and name each according to the activity you intend to measure.

Constructor

Stopwatch()

Constructs a Stopwatch object with both time and running status initialized to 0.

Member Functions

double real() const

Returns real time (clock time) in double-precision, floating-point seconds. You can call this function while the stopwatch is running.

void reset()

Resets the current time measurement to 0 without affecting the value of status() . If status() is initially nonzero, time measurement continues uninterrupted after resetting.

double resolution()

Returns the (system dependent) resolution of measured time in double-precision, floating-point seconds.

void start()

Begins measuring program execution time when status() is initially 0 ( status() becomes nonzero as a consequence of the call). If status() is initially nonzero, the call has no effect.

int status() const

Indicates whether the stopwatch is running (returns a value of 1) or not running (returns a value of 0).

void stop()

Halts measurement of program execution time when status() is initially nonzero ( status() becomes 0 as a consequence of the call). If status() is initially 0, the call has no effect.

double system() const

Returns the system CPU time in double-precision, floating-point seconds. You can call this function while the stopwatch is running.

double user() const

Returns the user CPU time in double-precision, floating-point seconds. You can call this function while the stopwatch is running.

System Environment

On OpenVMS systems, user time returns the total accumulated CPU time, and system time returns 0. Resolution is 1/100 second.

Example

Stopwatch w ; 
w.start() ; 
//...
// some computation you want to time goes here 
//...
w.stop() ; 
cout << "elapsed time was " << w.user() << "\n"; 
      

Displays the number of seconds the computation takes to run. The result is a double-precision value.