Re: [Discuss-gnuradio] fast dot product?

[Eric Blossom]

On Thu, Jul 27, 2006 at 12:47:46AM +0200, Jens Elsner wrote:
> Hello,
> 
> I'd like to calculate the complex dot product with GNU Radio.
> 
> Is there a way to do it faster that this? This correlation takes 
> "ages"...

You can probably repurpose the existing gr_fir_ccc.h code.
See gnuradio-core/src/lib/filter/gr_fir_ccc.h
It doesn't apply the conjugate, so you'll need to work that into your
b values.   If you use gr_fir_ccc.h, you'll get hand-coded SIMD
assembler on x86 and x86-64, and generic C++ code on the rest.

The set_taps operation is relatively expensive.  For our purposes, we
expected it to be done infrequently.  This allowed us to amortize the
cost of building multiple copies of the taps at different alignments.
This was required to take advantage of the 128-bit loads with SSE.

Eric