On Tue, 4 Aug 2009, leee wrote: > One of the big problems I had with FG was its pseudo asynchronous > operation, which still meant that the rates at which you could run > things like the FDM, autopilot and Nasal were effectively limited > by the frame rate and which could lead to an aircraft being stable > on one system but unstable on another. I would really like to see > these subsystems running on their own cores, or even more > preferably, on their own networked hardware, so that I could run > them at much higher and guaranteed rates.
Moving these tasks into different threads would only bring you a cart load of indeterminism due to the whims of the OS scheduler, page faults, interrupts, bus contention or network latency etc etc.. The crucial observation you missed here is that these tasks need to run interleaved at high (120+ Hz) guaranteed rates in /simulated/ time not necessarily in real time. (Sampling pilot inputs needs to be done at what rate? 30Hz?). Interleaving them in one thread is really the very best you can do assuming your processor core is fast enough (and I'd be surprised if it isn't, e.g. JSBSim needs in the order of 1% of the capacity of a not so current core to run a typical model in real-time). IMHO the one important threading benefit is if we could get all of the rendering off the main simulation loop, meaning that the model runs independent of the presentation. (Ok, expensive environment eye candy like the traffic manager or wild fire CA would also be beneficial to move into threads - but they don't have tight synchronization needs wrt the main aircraft.) Apart from that the potential for improvements with threading I can see is in the rendering system, and that's perhaps a more general OSG and OpenGL vendor playing field than a FlightGear one. Cheers, Anders -- --------------------------------------------------------------------------- Anders Gidenstam WWW: http://www.gidenstam.org/FlightGear/ ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
