[PD-dev] More clock questions

Sebastian Shader sebfumaster at aol.com
Tue Jun 15 17:03:23 CEST 2021

yes, it's in the github repo https://github.com/sebshader/lscore.the interface with pd using pdlua is lscore.pd_lua (relevant part is lscore:postinitialize() and the function self.score:clock_callback)
the scheduler stuff is mainly in lualibs/Score.lua (in Score:new() there's a delay() function in the prototype object, and there's also Score:callback() to deal with the priority queue stuff. the makepqmbr() function returns a new element for the queue with a new coroutine. the add() and addbase() functions add the new members to the priority queue) and the heap implementation is in lualibs/Heap.luait's a bit messy right now because I'm in the middle of (slowly) adding the new feature, maybe https://github.com/sebshader/lscore/tree/6ab3499ac5c3b53b2e40b6b01d50679f7975bd97 is better to look at.In my case I also made a system of dynamic scope, where the scope of any variable is in the nearest ancestor coroutine that defined it. (so if you create a "tempo" variable that variable will be accessible in all descendant coroutines sprouted from it, unless one redefines it)

-----Original Message-----
From: Iain Duncan <iainduncanlists at gmail.com>
To: Sebastian Shader <sebfumaster at aol.com>
Cc: pd-dev at lists.iem.at <pd-dev at lists.iem.at>
Sent: Tue, Jun 15, 2021 7:18 am
Subject: Re: [PD-dev] More clock questions

Thanks Seb, that's helpful and  gives me some stuff to chew on. Is the code in which you've done this public?
On Sun, Jun 13, 2021 at 9:40 PM Sebastian Shader via Pd-dev <pd-dev at lists.iem.at> wrote:

>1) Is the Pd clock scheduler only accurate to the ms or does it operate at>higher than ms accuracy? (As in, if I wanted to role my own mechanism
>closer to what Seb did, how frequently should my master time go off?)
from what I can tell Pd seems to use its own unit of time in order to interface better with the audio side of things, (but it's stored in a double)lua uses double for it's numbers, and I just used milliseconds (partially because the pd clocks seem to work/have worked with milliseconds primarily/historically)
I'm not sure I understand "how frequently should my master time go off?"
You have the clock callbacks stored in the priority queue, and use the scheduled time (in ms) for the keys the queue is sorted by.So in order to "start a delay", you put a callback on the queue. Then to start your scheduler, call the underlying t_clock delay with the value of the difference between the time of the top value in the queue (which will be the earliest callback because you set up the priority queue to sort as a min-heap, so that the lowest times get popped out first) and the current time.Every time you return from the underlying t_clock callback, increment your own time by the amount the underlying t_clock was called with/delayed for (in milliseconds stored in a double, in my case).
The nice thing about using t_clock is that you don't need to implement the delay part yourself, just the priority queue and figuring out when to start and stop it. (along with dispatching the callbacks associated with members in the queue, wherever those go.)
What I do is put my "main thread" on the queue to start. Every time another thread/coroutine is started/sprouted it gets added to the queue. Whenever a delay is encountered the current thread will be at the top of the queue, so you just have to change the delay time and call some downheap() function on the heap to restore the heap property after changing the delay time in the priority queue member. (then delay the t_clock by the new top member of the queue)Every time a coroutine finishes I take it off of the top of the queue. (and call another t_clock delay for the new top member, or stop if there are none left)

-----Original Message-----Message: 2
Date: Sat, 12 Jun 2021 11:11:12 -0700
From: Iain Duncan <iainduncanlists at gmail.com>
To: pd-dev <pd-dev at lists.iem.at>
Subject: [PD-dev] More clock questions

I have a couple more clock/schedule related questions after rereading the
comments from Miller and Seb.

1) Is the Pd clock scheduler only accurate to the ms or does it operate at
higher than ms accuracy? (As in, if I wanted to role my own mechanism
closer to what Seb did, how frequently should my master time go off?)

2) Miller made reference to the linked list of clocks that pd iterates
through. Is that something I could access directly? (and if so, where would
it live?

3) if anyone knows good books or online resources for learning more about
writing scheduler related code, I'm all ears! :-)

Pd-dev mailing list
Pd-dev at lists.iem.at

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.puredata.info/pipermail/pd-dev/attachments/20210615/b6d25448/attachment-0001.htm>

More information about the Pd-dev mailing list