High resolution timer via C++ ?

BlitzMax Forums/BlitzMax Programming/High resolution timer via C++ ?

Chroma

(Posted 2007) [#1]

I'm not sure we have access to a real high resolution timer natively in BMax. Can someone expound on this and if we don't, something should be workable in C++ I suppose.

TomToad

(Posted 2007) [#2]

I created this module a while ago. Works only with Windows.

Module toad.counter
Extern "Win32"

Function QueryPerformanceCounter(lpPerformanceCount:Long Var)
Function QueryPerformanceFrequency(lpFrequency:Long Var)

End Extern

Function GetTicks:Long()
	Local Ticks:Long
	
	If QueryPerformanceCounter(Ticks)
		Return Ticks
	Else
		Return 0
	End If
End Function

Function GetMillisecs:Double()
	Global Firstcall:Int = True
	Global Frequency:Long
	Local Ticks:Long
	
	If Firstcall
		QueryPerformanceFrequency(Frequency)
		Firstcall = False
	End If
	
	If QueryPerformanceCounter(Ticks)
		Return (Double(Ticks * 1000) / Frequency)
	Else
		Return 0
	End If
End Function

Put it in BlitzMax/mod/toad.mod/counter.mod/counter.bmx
You then use "Import toad.counter" at the top of your source.
GetTicks() will return the number of ticks since program start. The meaning of ticks is machine dependent, so it is best used for profiling and such.
GetMillisecs() will give you the number of milliseconds passed with double precision. This is great for more accurate timing in your code.
Note that not all machines support high resolution timers, especially older ones.

Chroma

(Posted 2007) [#3]

Note that not all machines support high resolution timers, especially older ones.

Thanks Tom. Does this mean that older machines will crap out using this method? Or will they return the default precision?

Damien Sturdy

(Posted 2007) [#4]

default precision.

My machine returns timings to some stupid precision but you wont actually know for sure if it is accurate.

My version; http://www.blitzbasic.com/codearcs/codearcs.php?code=1909

TomToad

(Posted 2007) [#5]

My code will return 0 if high resolution timers are not supported. Nowadays, it will be very rare to find a machine that doesn't support them. I'm not even sure if there is a DirectX7 capable machine that doesn't also support high resolution timers, so you should be safe with them.
If you want to be extra sure, you could always test first and set a flag.

Local HRFlag:Int = True
local TestTime:Long = GetTicks()
If Not TestTime Then HRFlag = False

While GameIsRunning
    Local Time:Double
    If HRFlag
        Time = GetMillisecs() 'Call High Resolution Timer
    Else
        Time = Millisecs() 'Call BMax Timer
    End If
Wend

Muttley

(Posted 2007) [#6]

Does anyone know if it's possible to use a high resolution timer on MacOS and Linux, and if so which calls are quired?

I've put together a little module that will setup a high-resolution timer, but if the timer is not supported or the platform os MacOS/Linux it will transparently use MilliSecs() instead so you can use it without worrying about platform.

Ideally of course I'd like to support high-resolution timers on all platforms...

Muttley

Brucey

(Posted 2007) [#7]

Does anyone know if it's possible to use a high resolution timer on MacOS and Linux

Yes.

and if so which calls are (re)quired?

I don't know off-hand. Try Google, or your favourite search engine :-)

Muttley

(Posted 2007) [#8]

Good to know Brucey, but Google failed to deliver which is why I posted here. :)

Brucey

(Posted 2007) [#9]

Some Linux info here : http://lwn.net/Articles/167897/

Brucey

(Posted 2007) [#10]

And some OS X info here : http://www.macresearch.org/tutorial_performance_and_time

Interestingly, the Linux link was atop the first page of the Google search, the Mac link, towards the bottom of the first page of that particular Google search....

Muttley

(Posted 2007) [#11]

Thanks for that, but why the attitude? Just because you happened to pick a better search term for Google than I did...

BTW, that Linux one is only really relevant for Kernels >= 2.6.16.

Brucey

(Posted 2007) [#12]

2.6.16+ has the best real-time support.
(although I believe there are kernel patches for earlier versions)

Some more information : http://www.timesys.com/timesource/real_time.htm