[Rock-dev] <base/motion_command.h>

[Janosch Machowinski]

On 29.11.2011 19:26, Sylvain Joyeux wrote:
> On 11/29/2011 02:20 PM, Matthias Goldhoorn wrote:
>> I currently cleaning up some "controllers" for this i would like to
>> check how old the last message really is.
>> I would prevent something like:
>>
>> if(last_message_time - base::Time::now()).toSeconds()>   foo) throw_error;
>>
>> do something....
>>
>> last_message_time = base::Time:now();
>>
>>
>> instead i would like to use
>>
>>
>> if(current_message.time - base::Time::now()).toSeconds()>   foo) throw_error;
>>
>> What make more sense from my point of view, all old controller dosn't
>> need to change, but i don't want to create and "not so good written"
>> controller only because, "yeah we think it make sense, but no we dont'
>> want to change because we dont't want changes in base stuff even it make
>> sense"
> Well.. Life is hard.
>
> I do find your attitude commendable. Now here are the hard facts: not
> everyone has a lot of time on their hand to update log files and make
> sure that everything is fine with the proposed change. So, unless there
> is a very important and good reason, changing base types should not be
> done whenever someone feels like it. Which is why we discuss and vote on
> this mailing list.
>
> Using base::Time::now() as the "last message timestamp" is suboptimal,
> agreed. Now:
>
> * if you make sure that you don't introduce latencies (i.e. know what
>     you are doing with the stream aligner, or even better not use it in
>     control loop), and introduce proper priorities and realtime tasks,
>     the latency that you are trying to measure here won't be a problem.
> * in general, if you are trying to implement timeout, well, the
>     difference between the "wakeup time" and "data time" are low enough
>     that you can still do timeouting.
For me this change looks reasonable.
As we do not (as far as I know) replay motion command,
I also don't see any problems with updating logs.
And it is bad practice to 'grave types into stone'. If there is
a good reason to change them do it. We introduced stable and
master for this reason !
Also I remember a rule that any type in base should have a
timestamp anyway...

+1 change it, makes sense

-- 
  Dipl. Inf. Janosch Machowinski
  SAR-&  Sicherheitsrobotik

  DFKI Bremen
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