Excellent!  This is good data to have -- I'll take a look at running those
tests when I get back to work on Monday.

Josh

On Fri, May 7, 2010 at 5:33 PM, Cedric Pradalier <
cedric.pradalier@mavt.ethz.ch> wrote:

> Cedric Pradalier wrote:
>
>> Hi,
>>
>> this discussion raised my curiosity, so I created a small test program to
>> evaluate the advantage of using shared memory. The program is quite simple:
>> on one end a publisher is creating an image of some size, and publishing it
>> with a timestamp given by ros::Time::now(), on the other end, a receiver is
>> receiving the image, and recording the difference between ros::Time::now()
>> and the image timestamp.
>>
>> I made this test for 1000 images, from 640x480x1, 640x480x3, 1500x1000x3,
>> 3000x2000x3. The results are summarised in the attached pdf.
>>
>> I also attach the test file so that someone can point out if something is
>> wrong in my test.
>>
>> The bottom line is: for big object, shared memory transfer reduces
>> significantly the delivery delay.
>>
>> I hope that helps.
>>
>
> I also add the variation of the reception interframe time in the plot, as
> delivery delay is not the only parameter affected by the type of transport.
>
> Best
>
>
> --
> Dr. Cedric Pradalier
> http://www.asl.ethz.ch/people/cedricp
>
>
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