Subject: Re: [linux-audio-dev] XAP spec & PTAF comments [merge]
From: Steve Harris (S.W.Harris@ecs.soton.ac.uk)
Date: Sat Feb 08 2003 - 14:17:13 EET
On Sat, Feb 08, 2003 at 12:09:59 +0100, David Olofson wrote:
> On Friday 07 February 2003 23.07, Steve Harris wrote:
> [...]
> > > You might ove the conditionals around a bit depending on which
> > > case you want to be the fastest, but I don't think it gets much
> > > more fun than that.
> >
> > The are branchless clamps, which save a few cycles.
>
> Cool. Would your average compiler generate that kind of code from
> clean if()s, or do you have to go SIMD? (I've only seen this in SIMD
> extensions and DSPs before, but I'm not up to date with the "normal"
> x86 or PPC instruction sets.)
Its not an instruction its just a bit of maths using fabs().
> Any wild ideas are welcome, of course! A bit of brainstorming never
> hurts.
Sure.
[silence detection]
> Besides, if you have seriously heavy plugins in combination with this
> "a few effects at a time" behavior, the host could probably optimize
> this a bit without plugins explicitly supporting it. It means the
> host has to test buffers and figure out a clean way of activating and
> deactivating plugins without side effects, but if the plugins, or
> whole sub nets of plugins can be disabled, it's still a big win.
> ...and doesn't require any API support whatsoever, apart from the
> (de)activation stuff, which is needed anyway.
You still have unpredicatable CPU load, which makes it pretty useless.
- Steve
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