Propeller Code Execution Time

Comments

• Thric Posts: 109

  2012-01-02 09:46 edited 2012-01-02 09:46

  i asked this question once too and I found this information really helpful: http://www.parallax.com/portals/0/propellerqna/
  of more specifically the Code Execution Time section: http://www.parallax.com/portals/0/propellerqna/
• JonnyMac Posts: 9,556

  2012-01-02 10:41 edited 2012-01-02 10:41

  The great thing about the Propeller is that it can time itself as the links above illustrate -- I use this feature all the time, particularly when refining code. A recent "real world" example: I wrote a piece of industrial control code that has to process (low bandwidth) messages from CAN and MODBUS inputs. The customer wanted the main code loop to run every second. I found, though, that the loop really only took about 280ms so I bumped most of it to 3x per second (every 333.33ms), with a very small update to call the sensors every second as desired. The result was that the device is much more responsive to CAN and MODBUS inputs.
  
  Do read the material referenced above, though here's a quick bit of code to show you how it works.
  

  pub main | elapsed
  
    term.start(RX1, TX1, %0000, 115_200)
    pause(1)
  
    term.str(string(CLS, "Timing Test", CR, CR))
    
  
    elapsed := -cnt                                               ' start the timer
  
    ' code to test here
    
    elapsed += cnt - 544                                          ' stop timer (remove instruction offset)
  
    term.dec(elapsed)
    
  
    repeat
      waitcnt(0)
  
• Publison Posts: 12,366

  2012-01-02 13:05 edited 2012-01-02 13:05

  Another source of the document can be found in the Applications Notes as a PDF:
  http://www.parallaxsemiconductor.com/an009
  
  All current Application Notes can be found at:
  http://www.parallaxsemiconductor.com/appnotes
  
• coryco2 Posts: 107

  2012-01-02 15:41 edited 2012-01-02 15:41

  Great! Thanks.
• coryco2 Posts: 107

  2012-05-23 18:11 edited 2012-05-23 18:11

  Does the code JonnyMac and the Application Notes describe work with Spin code containing method calls, or just for code within a single method? It seems logical that if I place the "start timer" code just before the method call and the "stop timer" code right after, that the time measured should be how long it takes to jump to that method, execute it, and return. But what actually happens if I instead place the start/stop code directly in the method that I'm calling is that I get a much longer time reading. Why would this be?
  
  
  That is, why doesn't this:

  PUB MainMethod
  
      Time := -cnt         'Read System Counter for code timing measurement (Start)
  
      MethodCall
  
      Time += cnt -544     'Read System Counter for code timing measurement (End)
  
  
  PUB MethodCall
  
      MethodCallCode
  
  

  
  ...just give me a slightly longer time value than this:
  

  PUB MainMethod
  
      MethodCall
  
  
  PUB MethodCall
  
      Time := -cnt         'Read System Counter for code timing measurement (Start)
  
      MethodCallCode
  
      Time += cnt -544     'Read System Counter for code timing measurement (End)
  
  
• kuroneko Posts: 3,623

  2012-05-23 18:25 edited 2012-05-23 18:25

  coryco2 wrote: »

  But what actually happens if I instead place the start/stop code directly in the method that I'm calling is that I get a much longer time reading. Why would this be?

  You tell us. I just tried and it works as advertised, measuring at top level I get $005B97E0 cycles, one level lower (without call overhead) it's $005B9590. MethodCallCode is a private method waiting for half a second. Can you cut down your code to a sample case and post it here?
• coryco2 Posts: 107

  2012-05-23 19:33 edited 2012-05-23 19:33

  Oops. Forgot I had an IF statement at the beginning of the method I was calling that was returning before completing all the called method's code (duh...).
  
  (The timing code actually works fine.)