Re: [Discuss-gnuradio] Parallel programming

[Michael Dickens]

Without seeing your GRC implementation or Python script & block's 
implementation code, mostly what I or anyone else can provide is general 
advice.  GNU Radio 3.3.0 uses the thread per block (TBP) scheduler by default; 
if you're not doing anything else except running the flow-graph (meaning: you 
don't set special GNU Radio environment variables or use a GNU Radio 
configuration file), then that's what you're using.  The performance of any 
flow-graph really depends on how complex the flow-graph is, how much data 
you're trying to push through it, and how fast your processors are able to 
perform the block's computations.  The host OS influences execution speed a 
little, but mostly its those listed factors that make the difference; that 
said, I haven't used GNU Radio on Ubuntu in a long time so I cannot talk about 
that OS specifically (Linux, in general, provides very low OS overhead & more 
time executing the flow-graph's computations).  It might be that your 
flow-graph is running fast enough already to use just 1 core; does it run in 
"real time" for what you need?  Rewriting a given block to use vector-based 
instructions (SSE, Altivec, Neon) often dramatically increases the computations 
/ time for that block.  As for parallelizing your block, without knowing what 
it is/does exactly, I would always advise you to break down the computations 
into smaller pieces and then implement those as blocks (if they are no 
already), then create the "meta-block" (I forget the exact name of it now; 
maybe "heir_block2"?) using those.  That way, the TBP scheduler will have more 
to work with and the flow-graph will end up being executed more in parallel.  
If your block has internal data-feedback, then the meta-block will not work 
(GNU Radio doesn't "do" data-flow feedback in the flow-graph) & you'll have to 
find some way of parallelizing your algorithm.  There are plenty of good books 
on this subject. - MLD

On Jan 10, 2011, at 3:11 PM, sirjanselot wrote:
> I am currently using gnuradio 3.3.0 as my version.
> How do I know that my flow-graph is executing in thread per block mode?
> 
> As far as I can tell my only 1 core out of the 8 is being used when I run my
> flow-graphs.  This is what I see when I run the performance monitor (or
> whatever it is called) in Ubuntu.
> 
> So can I parallelize my block without having to create a meta-block as you
> say?  I have a lot of for-loops and vector calculations that need to be
> optimized (adaptive fir filters).