On Thu, 23 Feb 2012 10:29:02 -0500
Tom Rondeau t...@trondeau.com wrote:
On Thu, Feb 23, 2012 at 4:39 AM, Sebastian Döring
sdoer...@rhrk.uni-kl.dewrote:
Hello,
in the context of spectrum sensing in the 2.4 GHz band
using a modified
version of the usrp_spectrum_sense.py script, I am
having problems with
high latency times.
Since the time for recording samples and all the tuning
stuff is supposed
to be much less than what I am currently dealing with
(something around
88ms between two center frequencies),
I was wondering if this might be a problem of some
additional calculations
the python script is doing with every message I get from
the c++ code.
In particular these calculations contain summing up the
vector I get from
the queue of the source and comparing the sum to a
previously calculated
threshold wrapped into some if-statements
Any statements highly appreciated.
Thanks.
-Sebastian
If it's latency in the flowgraph, you can try and use
the new
max_noutput_items (pass this value to tb.start(N) or
tb.run(N), whichever
is being used). The smaller this number, the faster
blocks will pass data
between eachother, but also the harder your computer is
going to have to
work to keep up.
If you think that the latency is due to Python
calculations, you can think
about finding a more efficient scipy implementation of
the calculations. If
one doesn't exist, you can write some C code and look at
the f2py program
that comes with Python; it's a simpler wrapper generator
than SWIG that
converts from FORTAN to Python, but I believe it nicely
supports C
functions as well.
Just a couple of thoughts.
Tom
Thanks Tom,
I have proofed your suggestions, but none of them seemed
to help much.
I also ran the script under cProfile to get a better
timing analysis and it turns out that
gr_py_msg_queue__delete_head is the real evildoer.
According to cProfile it takes 94ms per call. Since
cProfile produces some overhead itself, this is pretty
much what fits into these almost 90ms I measured myself.
Does anyone have an idea if and how this could be speeded
up?
Thanks
-Sebastian
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