Wrapper for the system time query methods. More...

#include <timer.h>

Public Member Functions
Construction / destruction
	Timer ()
	default constructor

Control
void	reset ()
	initialize timer, set timing accounts to zero.

void	start ()
	start timer, resume accounting user, system and real time.

Real	stop ()
	stop timer, return accounted user time.

Access
void	getTimes (Real userTime, Real systemTime, Real *realTime) const
	get accounted user, system or real time.

Real	userTime () const
	return accounted user time.

Real	systemTime () const
	return accounted system time.

Real	realTime () const
	return accounted real time.

long	resolution () const
	return resolution of timer as 1/seconds.

Private Member Functions
Internal helpers
Real	ticks2sec (long ticks) const
	convert ticks to secounds.

void	updateTicks () const
	get actual user, system and real ticks from the system.

Private Attributes
Data
long	uAccount
	user time

long	sAccount
	system time

long	rAccount
	real time

long	uTicks
	user ticks

long	sTicks
	system ticks

long	rTicks
	real ticks

Static Private Attributes
number of ticks per second
static const long	ticks_per_sec = long(TIMES_TICKS_PER_SEC)
	ticks per secound, should be constant

Types
enum soplex::Timer::{ RESET, STOPPED, RUNNING }	status
	timer status

Detailed Description

Wrapper for the system time query methods.

In C or C++ programs, the usual way to measure time intervals, e.g., running times of some complex computations, is to call one of the provided system functions like clock(), time(), times(), gettimeofday(), getrusage() etc. By these functions one can gather information about the process' user and system time and the system clock (real time).

Unfortunately, these functions are rather clumsy. The programmer determines computation times by querying a (virtual) clock value at the beginning and another one at the end of some computation and converting the difference of these values into seconds. Some functions impose restrictions; for instance, the values of the ANSI C function clock() are of high resolution but will wrap around after about 36 minutes (cpu time). Most timing functions take some data structure as argument that has to be allocated before the call and from which the user has to pick up the information of interest after the call. Problems can arise when porting programs to other operating systems that do not support standards like POSIX etc.

In order to simplify measuring computation times and to hide the system-dependencies involved, a concept of timers accounting the process' user, system and real time is implemented. C and C++ interfaces are provided as a set of functions operating on timers and a timer class respectively.

The idea is to provide a type Timer for objects that act like a stopwatch. Operations on such an objects include: start accounting time, stop accounting, read the actual time account and reset the objects time account to zero.

After initialization, accounting for user, system and real time can be started by calling a function start(). Accounting is suspended by calling a function stop() and can be resumed at any time by calling start() again.

The user, system or real time actually accounted by a timer can be accessed at any time by the methods shown in this code section:

    Real utime, stime, rtime;
      
    utime = timer.userTime();
    stime = timer.systemTime();
    rtime = timer.realTime();
      
    timer.getTimes(utime, stime rtime);

For convenience, the actually accounted user time is returned by stop() too. Function reset() re-initializes a timer clearing all time accounts.

Function resolution() returns the smallest (non-zero) time intervall which is resolved by the underlying system function: res = 1/Timer_resolution().

The process' user and system times are accessed by calling function times(), which is declared in <sys/times.h>. If OS supports POSIX compatibility through providing <sys/unistd.h>, set -DHAVE_UNISTD_H when compiling timer.c. Ignore compiler warnings about missing prototypes of functions.

Definition at line 95 of file timer.h.