Re: [PD] firm delay scheduling

2012-10-31 Thread IOhannes m zmoelnig 
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On 2012-10-30 18:13, Jean-Marie Adrien wrote:
 Hello I'm trying to launch security procedures in case of trouble, 
 that will respond in less than 250 msec. The fundamental question 
 is :
 
 Is there an object to schedule an event in the future with firm 
 absolute delay ?
 

if you want hard realtime, then you would need a system that is
capable of doing realtime. no standard (as in desktop) operating
system on the market will fullfill your needs.

so let's assume soft realtime (where a given piece of code has
'hopefully' been executed by a certain time) is good enough.

you are facing to different problems:

- - if your CPU is busy doing other things, there is no way for it to
also do your specific tasks. adding more CPUs might help if there are
*other* programs involved that eat your processing power.
it's not so easy if Pd itself is consming too much CPU: unfortunately
Pd is inherently single threaded, so there is no way to start your
security procedures if the main thread is busy having troubles,
short of running 2 Pd's in parallel (and let them communicate e.g. via
network)

- - you can experience the elastic nature (compared to your wall
clock) of [delay] even if your CPU does not run at 100%. Pd's logical
time is floating a bit (compared to real time) in order to be able to
prevent dropouts due to short  CPU load spikes. however (unless you
really max out your CPU for longer periods) the elasticity is limited,
and is basically a function of your audiobuffer settings in the
media settings dialog.
so try reducing the audiobuffer, or even run Pd without audio
(depending on your needs) and tune the -sleepgrain parameter, to get
a reasonably low jitter.

once you have done that, simply schedule your security procedures at
250-maxjitter in the future, which should make your system react at
most 250ms in the future, which seems to be what you have been asking for.


fgmasdr
IOhannes
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Re: [PD] firm delay scheduling

2012-10-31 Thread Roman Haefeli 
On Tue, 2012-10-30 at 13:42 -0400, Hans-Christoph Steiner wrote:
 [delay] is as firm as your going to get, from what I've seen.  [delay]
 should be at least as accurate to about one audio block, so like
 1.5ms, so if you only need 250ms accuracy, you have plenty of room.

[delay] is not somewhat precise, it is absolutely precise. However,
there are classes that ignore the precision of [delay] and treat
incoming messages as if they would have been sent at block boundaries.
For instance the phase inlets of [osc~] and [phasor~].

What Jean-Adrien probably means by 'elastic' is not the lack of
precision of [delay] in the deterministic scope of Pd, but the fact that
it tied to that deterministic scope and thus is precise only in logical
time, but not in real time. If the CPU load of Pd goes above 100%,
logical time gets more and more behind real time. 

Roman

 .hc
 
 On Oct 30, 2012, at 1:13 PM, Jean-Marie Adrien wrote:
 
  Hello
  I'm trying to launch security procedures in case of trouble, that will 
  respond in less than 250 msec.
  The fundamental question is :
  
  Is there an object to schedule an event in the future with firm absolute 
  delay ? 
  
  {realtime} measures time AFTER the problem (no scheduling)
  {del} schedules things but the delay is kind of elastic, depending on the 
  CPU load.
  
  thanks
  JM
  
  
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Re: [PD] firm delay scheduling

2012-10-31 Thread Roman Haefeli 
On Tue, 2012-10-30 at 18:52 +0100, Cyrille Henry wrote:
 hello,
 
 if your problem is detecting when cpu is over 100% so that delay is
 not acurate, then the best solution is some kind of external watchdog.
 
 just send a message every 10 ms to an other software, if this external
 software did not receive anything during the last 20ms, then there is
 a cpu problem on the pd side...
 
 
 the external software can be an other pd, a shell script (using
 pdreceive, or anything else.


An external watchdog will only help in detecting a timeout, but it won't
help prevent it. There probably is no way to stop Pd from doing what it
is currently doing as it will always first finish its current task
before it considers the next ( triggered by message from network, from
HID, etc.).


Jean-Adrien, I think you would have to design your patch in a way that
makes sure that no single task takes more than 250ms. If this is
possible at all depends on what your tasks look like. If tasks take too
much time, split them in smaller task. If every single task takes only a
fraction of the allowed timeout, you could ask [realtime] about how long
the last task took and decide whether you need to respond now or if it
is safe to execute another task.

Roman


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Re: [PD] firm delay scheduling

2012-10-31 Thread Jean-Marie Adrien 
Thanks everyone !
Best practical way is probably communicate with another PD on multiprocessor 
architecture though. 
This is what I had in thought, but I wanted to post before implementing.
JM


Le 31 oct. 2012 à 09:12, Roman Haefeli a écrit :

 On Tue, 2012-10-30 at 13:42 -0400, Hans-Christoph Steiner wrote:
 [delay] is as firm as your going to get, from what I've seen.  [delay]
 should be at least as accurate to about one audio block, so like
 1.5ms, so if you only need 250ms accuracy, you have plenty of room.
 
 [delay] is not somewhat precise, it is absolutely precise. However,
 there are classes that ignore the precision of [delay] and treat
 incoming messages as if they would have been sent at block boundaries.
 For instance the phase inlets of [osc~] and [phasor~].
 
 What Jean-Adrien probably means by 'elastic' is not the lack of
 precision of [delay] in the deterministic scope of Pd, but the fact that
 it tied to that deterministic scope and thus is precise only in logical
 time, but not in real time. If the CPU load of Pd goes above 100%,
 logical time gets more and more behind real time. 
 
 Roman
 
 .hc
 
 On Oct 30, 2012, at 1:13 PM, Jean-Marie Adrien wrote:
 
 Hello
 I'm trying to launch security procedures in case of trouble, that will 
 respond in less than 250 msec.
 The fundamental question is :
 
 Is there an object to schedule an event in the future with firm absolute 
 delay ? 
 
 {realtime} measures time AFTER the problem (no scheduling)
 {del} schedules things but the delay is kind of elastic, depending on the 
 CPU load.
 
 thanks
 JM
 
 
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Re: [PD] firm delay scheduling

2012-10-31 Thread Jonathan Wilkes 
Are you using a GNU/Linux OS?

If so, why not just change the pd-watchdog ping-back period from 2 seconds to
250 milliseconds and recompile?  Then run Pd with realtime priorities.

I guess the question is: what does pd-watchdog actually do when it doesn't 
receive
the response in time?  Isn't it supposed to kill Pd?

-Jonathan



- Original Message -
 From: Jean-Marie Adrien j...@jeanmarie-adrien.net
 To: Roman Haefeli reduz...@gmail.com
 Cc: pd-list@iem.at List pd-list@iem.at
 Sent: Wednesday, October 31, 2012 6:30 AM
 Subject: Re: [PD] firm delay scheduling
 
T hanks everyone !
 Best practical way is probably communicate with another PD on multiprocessor 
 architecture though. 
 This is what I had in thought, but I wanted to post before implementing.
 JM
 
 
 Le 31 oct. 2012 à 09:12, Roman Haefeli a écrit :
 
  On Tue, 2012-10-30 at 13:42 -0400, Hans-Christoph Steiner wrote:
  [delay] is as firm as your going to get, from what I've seen.  
 [delay]
  should be at least as accurate to about one audio block, so like
  1.5ms, so if you only need 250ms accuracy, you have plenty of room.
 
  [delay] is not somewhat precise, it is absolutely precise. 
 However,
  there are classes that ignore the precision of [delay] and treat
  incoming messages as if they would have been sent at block boundaries.
  For instance the phase inlets of [osc~] and [phasor~].
 
  What Jean-Adrien probably means by 'elastic' is not the lack of
  precision of [delay] in the deterministic scope of Pd, but the fact that
  it tied to that deterministic scope and thus is precise only in logical
  time, but not in real time. If the CPU load of Pd goes above 100%,
  logical time gets more and more behind real time. 
 
  Roman
 
  .hc
 
  On Oct 30, 2012, at 1:13 PM, Jean-Marie Adrien wrote:
 
  Hello
  I'm trying to launch security procedures in case of trouble, 
 that will respond in less than 250 msec.
  The fundamental question is :
 
  Is there an object to schedule an event in the future with firm 
 absolute delay ? 
 
  {realtime} measures time AFTER the problem (no scheduling)
  {del} schedules things but the delay is kind of elastic, depending 
 on the CPU load.
 
  thanks
  JM
 
 
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Re: [PD] firm delay scheduling

2012-10-30 Thread Hans-Christoph Steiner 

[delay] is as firm as your going to get, from what I've seen.  [delay] should 
be at least as accurate to about one audio block, so like 1.5ms, so if you only 
need 250ms accuracy, you have plenty of room.

.hc

On Oct 30, 2012, at 1:13 PM, Jean-Marie Adrien wrote:

 Hello
 I'm trying to launch security procedures in case of trouble, that will 
 respond in less than 250 msec.
 The fundamental question is :
 
 Is there an object to schedule an event in the future with firm absolute 
 delay ? 
 
 {realtime} measures time AFTER the problem (no scheduling)
 {del} schedules things but the delay is kind of elastic, depending on the CPU 
 load.
 
 thanks
 JM
 
 
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Re: [PD] firm delay scheduling

2012-10-30 Thread Cyrille Henry 

hello,

if your problem is detecting when cpu is over 100% so that delay is not 
acurate, then the best solution is some kind of external watchdog.

just send a message every 10 ms to an other software, if this external software 
did not receive anything during the last 20ms, then there is a cpu problem on 
the pd side...


the external software can be an other pd, a shell script (using pdreceive, or 
anything else.

cheers
c

Le 30/10/2012 18:13, Jean-Marie Adrien a écrit :

Hello
I'm trying to launch security procedures in case of trouble, that will respond 
in less than 250 msec.
The fundamental question is :

Is there an object to schedule an event in the future with firm absolute delay ?

{realtime} measures time AFTER the problem (no scheduling)
{del} schedules things but the delay is kind of elastic, depending on the CPU 
load.

thanks
JM


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Re: [PD] firm delay scheduling

2012-10-30 Thread Jonathan Wilkes 
- Original Message -

 From: Cyrille Henry c...@chnry.net
 To: pd-list@iem.at
 Cc: 
 Sent: Tuesday, October 30, 2012 1:52 PM
 Subject: Re: [PD] firm delay scheduling
 
 hello,
 
 if your problem is detecting when cpu is over 100% so that delay is not 
 acurate, 
 then the best solution is some kind of external watchdog.
 
 just send a message every 10 ms to an other software, if this external 
 software 
 did not receive anything during the last 20ms, then there is a cpu problem on 
 the pd side...
 
 
 the external software can be an other pd, a shell script (using pdreceive, or 
 anything else.

How is the second pd going to complete its computations on time when the CPU
is over 100%?

 
 cheers
 c
 
 Le 30/10/2012 18:13, Jean-Marie Adrien a écrit :
  Hello
  I'm trying to launch security procedures in case of trouble, that will 
 respond in less than 250 msec.
  The fundamental question is :
 
  Is there an object to schedule an event in the future with firm absolute 
 delay ?
 
  {realtime} measures time AFTER the problem (no scheduling)
  {del} schedules things but the delay is kind of elastic, depending on the 
 CPU load.
 
  thanks
  JM
 
 
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Re: [PD] firm delay scheduling

2012-10-30 Thread Simon Iten 
If you have a multicore  machine you should be fine...
On Oct 31, 2012 12:31 AM, Jonathan Wilkes jancs...@yahoo.com wrote:

 - Original Message -

  From: Cyrille Henry c...@chnry.net
  To: pd-list@iem.at
  Cc:
  Sent: Tuesday, October 30, 2012 1:52 PM
  Subject: Re: [PD] firm delay scheduling
 
  hello,
 
  if your problem is detecting when cpu is over 100% so that delay is not
 acurate,
  then the best solution is some kind of external watchdog.
 
  just send a message every 10 ms to an other software, if this external
 software
  did not receive anything during the last 20ms, then there is a cpu
 problem on
  the pd side...
 
 
  the external software can be an other pd, a shell script (using
 pdreceive, or
  anything else.

 How is the second pd going to complete its computations on time when the
 CPU
 is over 100%?

 
  cheers
  c
 
  Le 30/10/2012 18:13, Jean-Marie Adrien a écrit :
   Hello
   I'm trying to launch security procedures in case of trouble, that will
  respond in less than 250 msec.
   The fundamental question is :
 
   Is there an object to schedule an event in the future with firm
 absolute
  delay ?
 
   {realtime} measures time AFTER the problem (no scheduling)
   {del} schedules things but the delay is kind of elastic, depending on
 the
  CPU load.
 
   thanks
   JM
 
 
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