visualpython-users

[Visualpython-users] minor (if strange) bug with rate(x)

[Jason M. <jas...@vp...>]

Hi,

 

As I have mentioned before, I am working on a really cool program for
displaying lots of real time data graphically.

 

I am now working away so I have turned to running the script on my laptop
(which admittedly is a reasonably powerful DTR, though not as powerful as my
desktop).

 

My desktop runs at 125.0 fps pretty much bang on. (it's a quad core 3GHz AMD
Phenom with a dual head Quadro graphics card running XP).

 

But on my laptop the fps jumps all over the place, but centres on about 100
fps.  (This is a 3GHz dual core with a proper internal NVidia graphics card)

 

Now, the script *HAS* to run at a rate of at least 111.11 fps or it breaks
as the streaming data starts to back up and cease to be real time.

 

At first I thought perhaps my laptop was simply too slow to process the data
L - bum!! So I took out the rate(125) line, it went to 8k fps.  Hum, can't
be that then.

 

So I change the rate(125) line to rate(150) and bingo it now works, with a
rate of about 148.0 fps.  It is as though the calibration on the rate(x)
timer is a bit squiffy?

 

Any clues?

 

So, it looks like to make it portable I need a contiguous feedback
adjustment of the rate(x) - perhaps that feature should be part of the code?

 

Cheers,

Jason.

Re: [Visualpython-users] minor (if strange) bug with rate(x)

[Guy K. K. <guy...@au...>]

On Tue, 02 Nov 2010 10:54:17 Jason Morgan wrote:
> Now, the script *HAS* to run at a rate of at least 111.11 fps or it breaks
> as the streaming data starts to back up and cease to be real time.

I think in this case it would be better to evaluate using more loosely coupled 
coding, e. g. by using a producer/consumer design pattern. Have the receiving 
end run in a separate thread that can react immediately and chuck the data 
into a data structure that then can be updated in the GUI whenever needed.

Some knowledge of software engineering can be helpful here.

Guy

-- 
Guy K. Kloss
School of Computing + Mathematical  Sciences
Auckland University of Technology
Private Bag 92006, Auckland 1142
phone: +64 9 921 9999 ext. 5032
eMail: Guy...@au...

Re: [Visualpython-users] minor (if strange) bug with rate(x)

[Jason M. <jas...@vp...>]

As I said before, you can't use threads on windows for this as they switch
too infrequently.  I first tried this using piglet and multiprocessing, I
then get 10ms (which is obviously how frequently messages are passed by
windows between the processors), but try as I might I can only get
99.99999Hz as Pyglet's graphics uses a separate thread.

I did think of using message queues, (the producer/consumer model you
suggest) and then passing more than one message per display thread pass.
But why make things more complicated than they need be?  And you still run
into the lack of any thread priority so you can't guarantee windows running
the thread you want it to.  More of a problem, I would also inherent a 16ms
latency in the display output.

That is why Visual Python is so good and so fast.  No imposed architecture
to your code = simple fast execution.   
I got exactly what I want in just a few lines of code.  I only wish I'd
discovered it a year ago......

I'm no expert (I have no formal software training - I find courses too
pedestrian, so I read books), as a result I've been able to program in
various languages for about 30 years (25 in C and nearly ten in Python)....
so I know a few tricks.

-----Original Message-----
From: Guy K. Kloss [mailto:guy...@au...] 
Sent: 02 November 2010 00:51
To: vis...@li...
Subject: Re: [Visualpython-users] minor (if strange) bug with rate(x)

On Tue, 02 Nov 2010 10:54:17 Jason Morgan wrote:
> Now, the script *HAS* to run at a rate of at least 111.11 fps or it 
> breaks as the streaming data starts to back up and cease to be real time.

I think in this case it would be better to evaluate using more loosely
coupled coding, e. g. by using a producer/consumer design pattern. Have the
receiving end run in a separate thread that can react immediately and chuck
the data into a data structure that then can be updated in the GUI whenever
needed.

Some knowledge of software engineering can be helpful here.

Guy

--
Guy K. Kloss
School of Computing + Mathematical  Sciences Auckland University of
Technology Private Bag 92006, Auckland 1142
phone: +64 9 921 9999 ext. 5032
eMail: Guy...@au...