Nanosecond timing on OS X

wilbert · **Posted:** Sun Mar 04, 2012 3:25 pm

I usually use ElapsedMilliseconds() on OS X to time a routine.
If you want a more accurate result, you can use UpTime() which returns the up time of the computer or mach_absolute_time() which is a bit faster.

Code:

ImportC "/System/Library/Frameworks/CoreServices.framework/CoreServices"
  UpTime.q()
  AbsoluteDeltaToNanoseconds.q(end_time.q, start_time.q)
EndImport
  
start_time.q = UpTime()
; ... 
end_time.q = UpTime()
nano_seconds.q = AbsoluteDeltaToNanoseconds(end_time, start_time)

Even if you divide the result by 1,000,000 to get milliseconds, the result seems to be more accurate compared to ElapsedMilliseconds().
After a while ElapsedMilliseconds() runs behind a little.

Alternative (faster) approach ...

Code:

ImportC "/System/Library/Frameworks/CoreServices.framework/CoreServices"
  mach_absolute_time.q()
  AbsoluteDeltaToNanoseconds.q(end_time.q, start_time.q)
EndImport
  
start_time.q = mach_absolute_time()
; ... 
end_time.q = mach_absolute_time()
nano_seconds.q = AbsoluteDeltaToNanoseconds(end_time, start_time)

J. Baker · **Posted:** Sun Mar 04, 2012 11:51 pm

Very nice, thanks Wilbert!

wilbert · **Posted:** Tue Mar 06, 2012 9:10 am

Here's also a simple procedure if you want microseconds

Code:

ImportC ""
  mach_absolute_time.q()
  mach_timebase_info(*info)
EndImport

Procedure.q ElapsedMicroseconds(); microseconds as quad
  Static c.d = 0
  If c = 0
    mach_timebase_info(@c)
    c = 1e-3 * PeekL(@c) / PeekL(@c + 4)
  EndIf
  ProcedureReturn mach_absolute_time() * c
EndProcedure

Procedure.d ElapsedTime(); seconds as double
  Static base.q, c.d = 0
  If c = 0
    mach_timebase_info(@c)
    c = 1e-9 * PeekL(@c) / PeekL(@c + 4)
    base = mach_absolute_time()
  EndIf
  ProcedureReturn (mach_absolute_time() - base) * c
EndProcedure

J. Baker · **Posted:** Mon Jun 11, 2012 9:59 am

Cool, this seems to solve the stuttering issue that SetFrameRate() causes.

Code:

ImportC ""
  mach_absolute_time.q()
  mach_timebase_info(*info)
EndImport

Procedure.d ElapsedTime(); seconds as double
  Static base.q, c.d = 0
  If c = 0
    mach_timebase_info(@c)
    c = 1e-9 * PeekL(@c) / PeekL(@c + 4)
    base = mach_absolute_time()
  EndIf
  ProcedureReturn (mach_absolute_time() - base) * c
EndProcedure

InitSprite()

OpenWindow(0, 0, 0,1280, 720, "Scroll", #PB_Window_SystemMenu | #PB_Window_ScreenCentered | #PB_Window_MinimizeGadget)
OpenWindowedScreen(WindowID(0), 0, 0, 1280, 720, 0, 0, 0)

  CreateSprite(1, 128, 128)
   StartDrawing(SpriteOutput(1))
    DrawingMode(#PB_2DDrawing_Default)
     Box(0, 0, 128, 128, RGB(0, 0, 220))
   StopDrawing()
   
   X = 0
   start_time.d = ElapsedTime()
   
Repeat
 
  Event = WindowEvent()
 
  FlipBuffers()
  ClearScreen(RGB(235, 235, 235))
  ;SetFrameRate(60)
 
  DisplaySprite(1, X, 360 - 64)
  
  end_time.d = ElapsedTime() - start_time.d
  
  If end_time.d > 0.015
    X + 4
    start_time.d = ElapsedTime()
  EndIf
 
  If X = 1280
     X = 0 -128
  EndIf
 
Until Event = #PB_Event_CloseWindow

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Nanosecond timing on OS X

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