ACE_High_Res_Timer Class ReferenceA high resolution timer class wrapper that encapsulates OS-specific high-resolution timers, such as those found on Solaris, AIX, Win32/Pentium, and VxWorks. More...
Detailed DescriptionA high resolution timer class wrapper that encapsulates OS-specific high-resolution timers, such as those found on Solaris, AIX, Win32/Pentium, and VxWorks.Most of the member functions don't return values. The only reason that one would fail is if high-resolution time isn't supported on the platform. To avoid impacting performance and complicating the interface, in that case, <ACE_OS::gettimeofday> is used instead. The global scale factor is required for platforms that have high-resolution timers that return units other than microseconds, such as clock ticks. It is represented as a static u_long, can only be accessed through static methods, and is used by all instances of High Res Timer. The member functions that return or print times use the global scale factor. They divide the "time" that they get from <ACE_OS::gethrtime> by global_scale_factor_ to obtain the time in microseconds. Its units are therefore 1/microsecond. On Windows the global_scale_factor_ units are 1/millisecond. There's a macro <ACE_HR_SCALE_CONVERSION> which gives the units/second. Because it's possible that the units/second changes in the future, it's recommended to use it instead of a "hard coded" solution. Dependend on the platform and used class members, there's a maximum elapsed period before overflow (which is not checked). Look at the documentation with some members functions. On some (most?) implementations it's not recommended to measure "long" timeperiods, because the error's can accumulate fast. This is probably not a problem profiling code, but could be on if the high resolution timer class is used to initiate actions after a "long" timeout. On Solaris, a scale factor of 1000 should be used because its high-resolution timer returns nanoseconds. However, on Intel platforms, we use RDTSC which returns the number of clock ticks since system boot. For a 200MHz cpu, each clock tick is 1/200 of a microsecond; the global_scale_factor_ should therefore be 200 or 200000 if it's in unit/millisecond. On Windows QueryPerformanceCounter() is used, which can be a different implementation depending on the used windows HAL (Hardware Abstraction Layer). On some it uses the PC "timer chip" while it uses RDTSC on others.
Constructor & Destructor Documentation
Initialize the timer.
Destructor.
Member Function Documentation
global_scale_factor_ is set to gsf. All High_Res_Timers use global_scale_factor_. This allows applications to set the scale factor just once for all High_Res_Timers. Check High_Res_Timer.cpp for the default global_scale_factors for several platforms. For many platforms (e.g., Solaris), the global_scale_factor_ is set to 1000 so that <scale_factor> need not be set. Careful, a <scale_factor> of 0 will cause division by zero exceptions. Depending on the platform its units are 1/microsecond or 1/millisecond. Use <ACE_HR_SCALE_CONVERSION> inside calculations instead a hardcoded value.
Returns the global_scale_factor.
Sets the global_scale_factor to the value in the env environment variable. Returns 0 on success, -1 on failure.
Set (and return, for info) the global scale factor by sleeping for usec and counting the number of intervening clock cycles. Average over iterations of usec each. On some platforms, such as Pentiums, this is called automatically during the first ACE_High_Res_Timer construction with the default parameter values. An application can override that by calling calibrate with any desired parameter values _prior_ to constructing the first ACE_High_Res_Timer instance. Beware for platforms that can change the cycle rate on the fly.
Reinitialize the timer.
Start timing.
Stop timing.
Set tv to the number of microseconds elapsed. Could overflow within hours on windows with emulated 64 bit int's and a fast counter. VC++ and Borland normaly use __int64 and so normaly don't have this problem.
Set nanoseconds to the number of nanoseconds elapsed. Will overflow when measuring more than 194 day's.
Sets usecs to the elapsed (stop - start) time in microseconds. Will overflow on windows when measuring more than appox. 2^^54 ticks. Is still more than 48 days with a 4 Ghz counter.
Start incremental timing.
Stop incremental timing.
Set tv to the number of microseconds elapsed between all calls to start_incr and stop_incr.
Set <nsec> to the number of nanoseconds elapsed between all calls to start_incr and stop_incr.
Print total time.
Print average time.
Dump the state of an object.
Get the current "time" as the high resolution counter at this time. This is intended to be useful for supplying to a ACE_Timer_Queue as the gettimeofday function, thereby basing the timer calculations on the high res timer rather than wall clock time.
Converts an hrt to tv using global_scale_factor_.
For internal use: gets the high-resolution time using <ACE_OS::gethrtime>. Except on platforms that require that the <global_scale_factor_> be set, such as ACE_WIN32, uses the low-resolution clock if the <global_scale_factor_> has not been set.
Calculate the difference between two ACE_hrtime_t values. It is assumed that the end time is later than start time, so if end is a smaller value, the time counter has wrapped around.
Member Data DocumentationDeclare the dynamic allocation hooks.
Starting time.
Ending time.
Total elapsed time.
Start time of incremental timing.
Converts ticks to microseconds. That is, ticks / global_scale_factor_ == microseconds.
Indicates the status of the global scale factor, 0 = hasn't been set 1 = been set -1 = HR timer not supported
The documentation for this class was generated from the following files: Generated on Mon Sep 15 07:15:17 2008 for ACE by  1.5.5
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