[ros-users] ROS communication performance .

[Josh Faust]

>
>
> A while back, I did some basic profiling of the image pipeline and it
> looked like a large percentage of time was being spent de/serializing
> the data. For some reason packaging up 640x480x15fps uncompressed color
> images into messages and sending them over a wifi connection doesn't
> work that well when you are running on an Atom Processor.
>
> Improvements here might be useful, though the effort is probably better
> spent converting the image pipeline to use nodelets or waiting for
> another rev of Moore's Law.
>
>
Images are unfortunately just about the best case for serialization -- they
end up as mostly just a single big memcpy.  There is a deserialization
improvement that may be possible though, which I just codified in a ticket:
https://code.ros.org/trac/ros/ticket/3000


> On several occasions we have worried that ROS would be slow but our
> experience has shown that the best approach is to skip worrying about
> the performance of ROS and just get the code working. Once the code is
> working it is a lot easier to optimize and we have almost always found
> that the slowest part is our code or the WiFi connection.
>
>
This is good to hear, thanks.  That has been our experience as well in most
cases -- and nodelets seem to satisfy the others so far.

Josh
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