[chuck-users] implementing a "wait for signal with timeout"
haberg at math.su.se
Mon Jun 8 15:24:29 EDT 2009
On 8 Jun 2009, at 19:53, Robert Poor wrote:
> In real-time music making, sometimes you want to wait for a signal
> (e.g. event.broadcast()) OR for a specific time to elapse, whichever
> comes first. I've implemented ways to do this, but I'm not really
> satisfied with the code.
> Here's the problem: Lets say that your music is slaved to a
> metronome, and the metronome is allowed to change speed. You want
> your music to stay sync'd to the metronome. If you simply do:
> now + (1/tempo)::second => time next_beat;
> next_beat => now;
> you'll be in trouble if the metronome speeds up while you're
> waiting: your note will be late. The fundamental problem is that
> once you execute "next_beat => now;", you're committed to waiting
> and there's now way to break out of it, short of killing the
> thread. The problem with killing the thread is that you leak 88K
> with each thread (!!!).
> So here's the programming challenge: how would you implement a "wait
> for signal with timeout" that will block until it gets a signal OR a
> specified time has elapsed? Since each thread costs 88K in non-
> reclaimed memory, you may create threads, but your solution must re-
> use them.
You might check out the noteoff() function I implemented here:
There is a similar problem of future event rescheduling: a future
disconnect, that should be canceled, if there has been a new note-on.
So the future event gets a thread of its own, and when it awakens, it
checks if there has been a rescheduling - if so, it just cancels the
As 'chuck' does not have event scheduling and kill-threads was not
intended for massive use, this seems to be the only way. But it works
More information about the chuck-users