Re: [Discuss-gnuradio] Cannot Achieve 50MSPS Sampling Rate

[Marcus D. Leech]

> well, its 1 thread per block, but grc just generates the flow graph
> code, its technically out of the loop.
The unspoken text here is that Gnu Radio has two different scheduling 
"policies" for a flow-graph--the default
  for several years had been TPB (Thread-Per-Block).  Which improves 
your odds of "keeping up" with complex
  flow-graphs across many blocks.

But individual blocks don't, as a rule, perform operations across 
multiple threads.  There are exceptions--the FFT blocks
  now provide the *option* of doing their work across multiple threads. 
 But that's only worthwhile for very large
  FFT operations--20K bins or so or larger.   Computer science hasn't 
yet come up with any general-purpose way of
  converting serial algorithms into parallel ones that are 
*unconditionally better* that their serial counterparts.  So most of
  the blocks in Gnu Radio are essentially serial in nature, with 
occasional optimizations like the SIMD optimizations described
  earlier.

> > > Should have worded that more carefully. I can choose 8 or 16 bits over the
> > > wire. My thinking was that I might be able to increase the rate of
> > > decimation (on second thought, decimation has more to do with sampling
> > > frequency than a data bottleneck) and also decrease the precision and use
> > > an integer less than 8bits. Basically, I thought ethernet may have been
> > > the bottleneck. Decreasing precision shouldn't be necessary, I'm just
> > > trying to build an understanding here.
There's no support for anything other than 16-bit or 8-bit (I and Q) 
samples on the wire.  In some wide-band applications, like
  radio astronomy, using fewer bits to gain bandwidth is pretty 
commonplace.  But in general-purpose SDR platforms, not so
  much.  But more importantly, handling 50Msps and *doing anything 
useful* present significant challenges if you want to "do those things"
  on a general-purpose compute platform.





--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org