StopWatch Class Reference

#include <StopWatch.hpp>

Public Member Functions
	StopWatch ()
	~StopWatch ()

Static Public Member Functions
static vector< string >	report ()
static void	start ()
static void	stop ()

Detailed Description

This class enables timing of code snippets by summing the elapsed time for each pass through the snippet. It uses the standard C++ high-resolution clock for maximum precision. The accuracy of the results is platform-specific, as it depends on the resolution of the underlying time measurement and by the time needed to start and stop the watch.

The functions in this class are not thread-safe and not re-entrant. The results are meaningful only if the application uses just a single execution thread and no other processes consume time on the computer. Even then interpreting timings is tricky. For example, some modern desktop systems dynamically change the CPU clock speed depending on the processor's chip temperature, and the placement of data in memory blocks relative to the processor core in use may substantially affect performance.

This class offers 5 global (i.e. application-wide) timers numbered from 1 to 5. The timers are nested, i.e. timer n+1 can only be started when timer n is already running. Vice versa, timer n can only be stopped when timer n+1 is no longer running. At the start of the application all timers are initialized to zero and the nesting level is set to zero as well. A call to the static start() function increments the nesting level and starts the timer corresponding to the new level. A call to the static stop() function stops the timer corresponding to the current level and decrements the nesting level. If the nesting level goes out of range, a fatal error is thrown. To access the timing results, the static report() function returns a list of strings reporting information on all nonzero timers in a human-readable format.

Rather than explicitly invoking the static start() and stop() functions, an instance of the StopWatch class can be used to ensure correct nesting of the timings: the constructor simply calls start() and the destructor calls stop(). For example, to time the execution of a complete scope, regardless of the scope's exit point, construct a StopWatch instance at the start of the scope:

{
    StopWatch watch;
    ...
    if (...) return 1;
    else if (...) return 2;
    ...
}

Constructor & Destructor Documentation

StopWatch()

StopWatch::StopWatch

(

)

The constructor calls the static start() function to start the timer at the next nesting level.

~StopWatch()

StopWatch::~StopWatch

(

)

The destructor calls the static stop() function to stop the timer at the current nesting level.

Member Function Documentation

report()

static vector< string > StopWatch::report ( )

static

This function returns a list of strings reporting information on all nonzero timers in a human-readable format. When this function is called, none of the timers may be running. If all timers are still zero, the function returns an empty list.

start()

static void StopWatch::start ( )

static

This function increments the nesting level and starts the timer corresponding to the new level. If the nesting level goes out of range, a fatal error is thrown.

stop()

static void StopWatch::stop ( )

static

This function stops the timer corresponding to the current level and decrements the nesting level. If the nesting level goes out of range, a fatal error is thrown.

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The documentation for this class was generated from the following file:

• StopWatch.hpp