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Re: [certi-dev] CERTI and Real-Time simulation
From: |
Eric Noulard |
Subject: |
Re: [certi-dev] CERTI and Real-Time simulation |
Date: |
Tue, 27 May 2008 11:31:14 +0200 |
2008/5/27 HADJ AMOR HASSEN <address@hidden>:
> Hi,
>
> I am using 2 real-time simulators (control federate and a graphical
> federate). I used CERTI to communicate between both simulators. It works
> fine! Also, i synchronize both simulators to start simulating at the same
> time using annouceSynchronizationPoint. It works fine also. For the first
> simulator, i developed a wrapper to communicate with CERTI. For the second
> simulator, i integrated HLA services in the code because this simulator is
> based in C++ language.
>
> This is an overview of my thesis work.
>
> I have some questions and i hope if someone can answer me.
>
> - The both simulators are real-time. Does this mean that we don't need to
> use Time management services? (non regulating or constrained simulator). I
> done a first test and it seems working fine.
What are the criteria for "working fine"?
> The both simulators are non
> regulator and non constrained and so they didn't request time advancing.
>
> - I done another test using one simulator as regulator and the graphic
> simulator as constrained. I used a time stepped simulation. The simulation
> slows hugely.
Can you gives us figures?
(and tell us how you did get teh measures)
How fast is your "not regulator + not constrained" compared to
"regulator + constrained"?
Can you give us the number of TICK_REQUEST in both cases?
Which kind of tick call do you use?
tick() --> classical non blocking tick
tick2() --> CERTI specific blocking somehow like tick(0,MAX)
tick(min,max) --> RTI will spent between min and max time in tick.
> Any idea?
You should tell us more details about your realtime requirement?
Do you need a 200Hz cyclic simulation ?
Do you need a sporadic simulation with contrained latency for UAV?
Do you need to preserve causality or is best-effort with eventual loss OK?
> Finally, I think that HLA shows an apparent weakness when it comes to
> real-time simulation applications.
You may be right (for your testcase) but
I think you didn't gives us enough informations to conclude.
We did successfully experiment 10 to more than 100Hz cyclic and
realtime simulation
with CERTI (2 up to 4 federate), it's doable but it doesn't come
"out-of-the-box" from
HLA.
I think high-performance application barely comes out-of-the box, you need
to be careful. You may use an RTOS but if you application breaks
ReaTime (RT) usual constraints
(minimize I/O, beware system calls, examine algorithm complexity, try
to use lock-free data structure...)
you won't get RT behavior from the best RTOS.
>
> Any suggestion, any idea or remark is welcome.
Gives us more details :=)
--
Erk