Add real time factor to log output

[restenb]

A suggestion came in through a project partner of ours to add support for logging real time factor to the result CSVs.

[kyllingstad]

My first thought was “sure, why not?” But then I realised that this is different from everything else in the output files. What we're currently logging is all related to the simulated system, and in most cases the results will be deterministic. The RTF, on the other hand, is related to the simulator – it is more of a performance thing, and it is not deterministic: Run the simulation twice, and you will get different RTF series. Also, logging the RTF may affect the RTF.

Therefore, at the very least, it should be optional (and opt-in), and it should be logged to a separate file.

[restenb]

After discussion in the committee meeting yesterday, we agreed that it would make sense to expand this into support for opt-in performance logging in general. Including things like:

• step time for each simulator
• network latency for distributed configurations
• information from the thread pool that schedules each step
• ... and more