Hi all,
Just wanted to post some findings in relation to control, as discussed above.
I tested today the latest version I could get hold of from the faust
git repo (e11a0156a, looks like version 2.28), and I found that...
control does indeed work in the way I described earlier in this
thread! That is, it only evaluates its contents (in particular, their
side effects) when its trigger is nonzero. I'm not sure if this is a
change since that discussion, or if I just wasn't testing then on a
recent enough version, or if I was hitting a bug (see below), but this
did not appear to be the case when I tested it before.
To demonstrate this behaviour, here is a a counter which we enable
with control every second sample. It really is only evaluated when
it's triggered, so the side effect (decrementing its internal
variable) only happens then. As a result, each value is output for two
samples, as desired:
import("stdfaust.lib");
process = control(-(1)~_, ba.time : %(2) : ==(0)); // -1, -1, -2, -2,
-3, -3, ...
But there is a bug here, I guess the same one that Oleg points out. I
believe this is probably what confused me before:
import("stdfaust.lib");
process = control(+(1)~_, ba.time : %(2) : ==(0)); // 1, 2, 3, 4, ...
In this case the counter is incremented every sample because the
compiler detects +(1)~_ as a duplicate of the same expression inside
ba.time, and optimises the process by letting them share the same
calculation, even though one of them should always be calculated and
the other should not. It seems that expressions inside a
control/enable should not be eligible for this optimisation. I will
probably file a bug report for this on github.
I haven't yet really tested how this works with vectorisation and the
various architectures. (Personally, I am most interested in using it
with faust2faustvst and faust-live.)
But Til, I believe this means you could use control to build something
analogous to demand-rate structures in SC. Let me know if you would
like a hand converting a simple example.
Cheers,
James
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