[ndnSIM] how to trace the self-defined element in ndnsim?

yao hu huyao0107 at gmail.com
Sat Apr 13 08:46:38 PDT 2013

Hi Alex,

Thanks very much for your guidance.
After I tried following your instruction, however, I still felt a little
confused by the callback to the trace source. Simply speaking, I defined a
uint32_t array in ndn-forwarding-strategy.cc which will continuously store
the incoming faceid information when simulation runs. If I just want to
record the values of each element in this array into a local file using ns3
tracing, how should I select a simple way to do this? Just using NS_LOG or
something is possible?

Thanks a lot again~


2013/4/13 Alex Afanasyev <alexander.afanasyev at ucla.edu>

> Hi huyao,
> Technically, you have many options how to trace self-defined variables.
>  If you really want to, you can just directly dump the values to std::cout
> or to some file.
> If you want to go with NS-3-style tracing, you would need to use either
> TraceSource, with which you explicitly notifying (somebody, who is
> configured in the simulation scenario using Connect calls) before or after
> you change the value.
> There is also a TraceValue, which can automate some notification tasks, if
> you're tracing just a value.
> Both methods require a couple of things.  For TraceSource, you need to
> define a local TracedCallback (like this
> https://github.com/NDN-Routing/ndnSIM/blob/master/model/fw/ndn-forwarding-strategy.h#L482)
> and then define a way to connect to this variable in GetTypeId method (like
> this
> https://github.com/NDN-Routing/ndnSIM/blob/master/model/fw/ndn-forwarding-strategy.cc#L71).
>  Afterwards, you just use the locally defined TracedCallback as if it is a
> function (like this
> https://github.com/NDN-Routing/ndnSIM/blob/master/model/fw/ndn-forwarding-strategy.cc#L586
> ).
> For TracedValue, you need to define the variable that you want to trace in
> a slightly different way (it is no longer a simple variable), like this
> https://github.com/NDN-Routing/ndnSIM/blob/master/apps/ndn-consumer-window.h#L98.
>  Then add a line into GetTypeId call, similar to this
> https://github.com/NDN-Routing/ndnSIM/blob/master/apps/ndn-consumer-window.cc#L65
> .
> To connect to variables, you need to use either
> Config::Connect/Config::ConnectWithoutContext method, or Object's
> TraceConnect (
> http://www.nsnam.org/doxygen-release/classns3_1_1_object_base.html#ada3a45b34bc23114a25e0ab19188276e
> ).
> Let us know if you have more questions.  If you can give more specific
> description of what you want to trace, then we may give more concrete
> suggestion of what is the best way to do it.
> ---
> Alex
> On Apr 12, 2013, at 9:37 AM, yao hu <huyao0107 at gmail.com> wrote:
> Hi Alex,
> Maybe this is not related to ndnsim, just about ns3. Could you please give
> a hint about how to trace or record the value of some self-defined variable
> like each element in some array somewhere in ndnsim when simulation runs?
> Thanks a lot!!
> Regards,
> huyao
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