Re: [Audacity-devel] multithreading

[Richard A. <ri...@au...>]

On Fri, 2009-01-30 at 08:46 +0300, LRN wrote:
> > Though programming in multithread is harder than normal one, since the
> > CPU enters a era of SMP even many-core, this feature is worthwhile.
> > And as to the OpenCL or CUDA, they are still too new and far too
> > limited for putting into generic use.
> [1]"Do two things simultaneously" scheme requires Audacity redesign - it
> has to be more threaded. OpenCL wouldn't help here. Recent
> OnDemandLoading feature is an example of threaded design.
> [2] "Do one thing in two threads, which makes it go ~2 times faster"
> requires special implementation. That's where things such as OpenCL
> would help. But it's not cost-effective to rewrite everything in
> SMP-style. Only costly operations should be made parallel, everything
> else would benefit more from threaded design (see [1]).

Well put. Audacity has both CPU-bound and IO-bound effects, and quite a
few where the balance is not far off even, depending on how good your
CPU and HDD are.

Redesign to do multiple things at once is _very_ hard work to do well
and completely (think how much Micheal has had to do to stop his import
threads treading on each others toes).

Multi-threading single sections on a case-by-case basis is obviously
less universal, but can be a shorter way to obtain a seriously quicker
run of that effect. Unless the code inside the effect is seriously ugly
to start with, it should be less work to do.

Richard