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; play_note(); 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: https://lists.cs.princeton.edu/pipermail/chuck-users/2009-May/004183.html 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 event. 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 just fine. Hans