On 01/24/2012 07:12 PM, Nick Foster wrote:
On Tue, Jan 24, 2012 at 9:56 AM, ziyang <address@hidden>
wrote:
On 01/19/2012 07:13 PM, Nick Foster wrote:
Optimizing an algorithm is a hard and sometimes
counterintuitive process. You might benchmark the
following:
- Gnuradio's atan2 WITHOUT any Volk multiplications (just
comment out the volk mults in your block)
- The Volk multiplications WITHOUT Gnuradio's atan2 (just
comment out the atan2 in your block)
This will let you determine where the bottleneck is. In
addition, try running over a MUCH larger dataset. The
clock resolution at <1ms is not very good and the
scheduler will have a correspondingly larger effect at
smaller timescales.
I think you'll find the atan2 part takes vastly longer
than the multiplications do, and that will be where you
have to look for performance improvements.
--n
I have been doing some tests about the demodulation module. As
you said, the atan2 part takes much longer than the
multiplication. So in order to maximize the performance
improvement that volk could bring to the processing, I took a
division and a multiplication out of atan2, and use volk-ified
divider and multiplier instead. Then I run tests using a much
larger dataset.
But from the test results, I did not observe a performance
improvement. In fact, the average processing time even
increase a little bit. So I was wondering if what I did was
not a good way to improve the performance?
Another issue is that when I ran Cmake to build Gnuradio on
E100, it reported this:
-- Available arches: generic;neon
-- Available machines: generic;neon
-- Did not find liborc and orcc, disabling orc support...
But from the "opkg list-installed | grep orc" check, both orc
and liborc are installed. Could this lack of orc support be
part of the reason why my implementation did not have a
performance improvement?
Very likely. Make sure that orcc is somewhere that
pkgconfig can find it, and make sure its version is >
0.4.10.
This is what it shows when I run a "opkg list-installed | grep orc"
check:
liborc-0.4-0 - 0.4.16-r1.0.9
liborc-test-0.4-0 - 0.4.16-r1.0.9
orc - 0.4.16-r1.0.9
I don't understand why orc/liborc cannot be detected by CMake. The
options for CMake are:
cmake -DCMAKE_INSTALL_PREFIX=/usr
-DCMAKE_CXX_FLAGS:STRING="-mcpu=cortex-a8 -mfpu=neon
-mfloat-abi=softfp -g" -DCMAKE_C_FLAGS:STRING="-mcpu=cortex-a8
-mfpu=neon -mfloat-abi=softfp -g" ../
Could you tell me what might be the problem? Thanks.
Terry
|