[chuck-users] Question on Shred Scheduling

Mike McGonagle mjmogo at gmail.com
Mon Jun 12 16:59:38 EDT 2006

I am working on a complete rewrite of my Masking package (the original
was too bulky and dependant on creating hundreds of shreds), and was
wondering just how something is scheduled in ChucK.

Basically, I am trying to create a single shred that handles the
updating of various parameters (as opposed to the original which had a
shred for each parameter), and in doing so, I would like to create a
"locking" mechanism around an array used to control which parameters
get updated, and when.

On one shred, there is the code that controlls the updating of
parameters, this shred runs for the life of the program (or some
portion of). On the second shred (most likely the main shred), the
array containing the references to the parameters to be updated needs
to be locked to prevent having a new reference added while the first
shred is actually updating the parameters. (Does this make sense?)

So, what I would like to know is how the following code would execute.

now + 0::ms => now;

Would this push the execution of the code to follow to the end of the
current time slice? Or is this functionality undefined, and would it
execute these shreds in an arbitrary fashion? In a nut shell, this is
the code from the updating shred that locks the array...

(this is embedded in an object)
false => int locked;
false => int keepGoing;
MController @ controllers[];  // this gets initialized to match the
number of controlled parameters

fun void helper(....) {
   true => keepGoing;
   while(keepGoing) {
      while(locked) {
         now + 0::ms => now;
      true => locked;
      for(0 => int i; i < controllers.cap(); i++) {
         if (controllers[i] != null) {
            <<< "do something with this controller", "" >>>;
      false => locked;

The variable 'locked' controlls the access to the 'for' loop, and the
variable 'keepGoing' controlls the outer loop. 'keepGoing' is set to
true at the top of this code, but will be set to false by another
shred to force the 'helper' function to exit as needed. The array
'controllers' is accessed by both this shred, as well as the main
shred to add

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