Re: [Bluez-devel] sbc decoder unrolled

[Brad Midgley <bmidgley@xmission.com>]

Victor,

Yeah, the only thing I didn't like about it is adding a bunch of 
computed array index and index modulo operations... I think we end up 
coming out ahead but I didn't test it specifically.

I could also double the size of sbc_proto_x_x0 and then I wouldn't have 
to worry about the modulo ops wrapping around our indexing into it. That 
will hurt any kind of caching of the array however.

Brad

Victor Shcherbatyuk wrote:
> Brad,
> 
> I'll check if I can do the same for the encoder, getting rid of that
> array shifting might speed up the stuff (well, it will probably add some
> array index operations which might make things worse, but we will see).
> 
> Regards,
>     Victor.
> 
> -----Original Message-----
> From: bluez-devel-admin@lists.sourceforge.net
> [mailto:bluez-devel-admin@lists.sourceforge.net] On Behalf Of Brad
> Midgley
> Sent: Friday, September 09, 2005 7:37 AM
> To: BlueZ Mailing List
> Subject: [Bluez-devel] sbc decoder unrolled
> 
> Hey
> 
> woohoo... I worked over the decoder a lot more and finally unrolled &
> committed it. It still uses floating point for now.
> 
> I was very proud of the fact that I found a way to rotate which
> sbc_proto_x_x0 value we choose rather than shifting matrixed values
> around in every loop. It's even more clear that the implementation they
> illustrate in the spec is meant to make the algorithm clear but not be
> an efficient way to do it.
> 
> I don't know how the instruction cache size in arm compares to x86. I
> haven't checked to see yet if unrolling is as big a win on xscale. fwiw,
> it cut x86 cpu use by about 50% over the looped code.
> 
> I'll look at fixed point next.
> 
> Brad
> 
> 
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