Re: [Discuss-gnuradio] Google Summer of Code 2014 applicant : Optimization with VOLK

[Bogdan Diaconescu]

Hi  Abhishek,

When implemented gr-dvbt (https://github.com/BogdanDIA/gr-dvbt) I used VOLK in 
many places to speed-up the processing. However, there is a great deal of 
speed-up that still need to be achieved on both Tx/Rx in order to lower cpu 
cycles consumption so there are a lot of challenges in the project from this 
point of view.

For example the Viterbi implementation is done using intrinsics instead of 
using VOLK just because when I used VOLK it was quite slow, achieving only 
16mbps of processing per single thread (7-8mbps on just C implementation).
Using intrinsics it raised the spead to 32-37mbps per thread which is quite 
good but the code is not directly portable. So, a good Viterbi decoder that 
achieves easily over 60mbps speed at input is still necessary probably not only 
in dvb-t implementation but perhaps in other applications. Just to add more to 
the challenge one may want to have a readable code beside the necessary speed 
(Spiral viterbi implementation is on the opposite side).

The OFDM synchronization code is also very time consuming and although uses 
VOLK already it can be using with great benefit new AVX2 instructions. Actually 
many of the blocks can use new instructions to speed-up the data processing.

Basically, for dvb-t on it's maximum speed with OFDM FFT 8k, QAM-64 and 
puncturing rate 7/8 the output of video is of 32mbps which means more than 
60mbps of processing speed after de-puncturing. A bigger challenge would be 
implementing real life DVB-S receiver where the data rate is over 50mbps at 
video output :) ).

This is just my short insight of challenges one may face when dealing with 
speed optimizations in a modern communication project.

Bogdan


--------------------------------------------
On Sun, 2/23/14, Abhishek Bhowmick <address@hidden> wrote:

 Subject: [Discuss-gnuradio] Google Summer of Code 2014 applicant : 
Optimization with VOLK
 To: address@hidden
 Date: Sunday, February 23, 2014, 8:52 AM
 
 Hello,
 I have completed a Bachelor's degree in
 Electrical Engineering from IIT Bombay, India and will be
 joining a masters program in Computer Science in August. For
 the summer, I am interested in participating GSoC 2014 and
 GNU Radio is an organization where my background fits
 nicely.
 
 
 I went through the ideas page and was
 particularly interested in doing performance optimization
 with VOLK. After going through some online documentation
 about the library and the SDR'12 paper, I realised that
 following areas need work :
 
 1. Profiling GNU radio code to identify new
 kernels and implement them for existing Intel SIMD
 extensions, also porting kernels to other ISA extensions.
 2. Better testing of the effects of more complex
 scheduler logic on larger environments (beyond simple
 kernels)
 
 3. Exploring extension of Volk to GPU ISAs, to
 leverage chips such as AMD Fusion (However, this seems to
 more research than software development)
 
 According to the GSoC proposal, point (1) seems
 to be the expectation. Given this, I would like some advice
 on how to go ahead looking for potential ideas (and some
 feedback on feasibility of the other ideas as well)
 
 
 My background : C++, Python, Signal Processing,
 Computer Architecture
 
 Thanks,
 Abhishek Bhowmick
 
 
 -----Inline Attachment Follows-----
 
 _______________________________________________
 Discuss-gnuradio mailing list
 address@hidden
 https://lists.gnu.org/mailman/listinfo/discuss-gnuradio