Re: [Discuss-gnuradio] Re-writing blocks using intel libraries

[Dan Halperin]

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Eugene Grayver wrote:
> Please see answers in-line.
>   Which blocks are causing you the biggest problem?
> 
> I got a 2x improvement on all the filtering blocks.  About a 40% 
> improvement for sine/cosine generation blocks.  This includes gr_expj, 
> gr_rotate.

I should mention that gr_rotate's performance can be _greatly improved_
by a simple change that, rather than rescaling the multiplier every
iteration, rescales every k, e.g. k=1000. I think I have an earlier
mailing list post about this. IIRC, the patch didn't go in because there
seemed to be no consensus about what k to use...
> We would not accept the changes.  Part of what we're up to is building
> an ever expanding universe of free code.  Instead of using the
> non-free IPP code, please consider using a free library such as ATLAS,
> or help us find and fix performance challenges in a way that doesn't
> require non-free code.  Also, are you sure that your performance
> issues can't be better addressed with an algorithmic change?  If
> you're using a lot of very low-level blocks (e.g., add, multiply,
> etc.) you're probably better off writing a block that aggregates some
> of the operations into a single block.
> 
> That's what I expected.  We'll try to contribute the more dsp-centric 
> blocks such as demodulators. 

That said, if you put the code (and/or the modified makefiles) up
somewhere, I'm sure there are some users that would benefit even if it
doesn't make it into the main release.

- -Dan
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