[PD] finding which instance executes first

Hans-Christoph Steiner hans at eds.org
Tue May 16 19:05:39 CEST 2006

On May 16, 2006, at 12:17 PM, IOhannes m zmoelnig wrote:

> Frank Barknecht wrote:
>> Hallo,
>> Hans-Christoph Steiner hat gesagt: // Hans-Christoph Steiner wrote:
>>> I am about to start working on the [hid] v2 stuff, and I just had  
>>> a thought.  Is there any way to find out which instance of an  
>>> object executes first?
>>> My idea is to have the first instance of the [hid] object do the  
>>> reading of event data from the OS and write it to memory.  Then  
>>> every other instance will just output the data from memory.  But  
>>> in order for this to work properly, the first instance to execute  
>>> needs to do the data-getting.
>> There was a thread about singletons a while ago, which resulted in  
>> the
>> singleton.pd that is used in [sssad].
> but isn't this something different? i think, hans's problem is with  
> execution-order at run-time and not with creation order at load-time.

yes indeed.  Also, I was thinking in C space, but maybe I should be  
thinking in Pd space.

> hans:
> what is wrong with threads here? i do think that threads is the way  
> to go when interfacing objects that might block the main thread  
> (and i am pretty sure that using libusb is prone to blocking)

In the case where the OS is already buffering, like HID, and perhaps  
USB, then you can just read from that buffer as long as there is data  
and the time slice isn't over.  That's how [hid] currently works.

> a thread-less solution would be to get the difference of _logical_  
> time since the last "bang" of the object and do the data-retrieval  
> only if this time is >0 (or better: !=0)

Hmm, that's easy.  Perhaps I should do this in Pd space. But that  
leads me to a question: if I change the block size of a patch with  
[switch~], does that change how often the messages are processed?  So  
if I want to have really low latency message processing, could I do  
[switch~ 16]?  Linux can get mouse events every 1 ms when tuned  

Is this going to take a lot more CPU time that C?  I'd like to do it  
in Pd, but [hid] can already use quite a bit of CPU at low latency  
(1-5 ms).




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