On Tue, 1 Apr 2008, LeeE wrote:

> Hmm...  [looks at watch and wonders if it's time to post another
> missive about the _need_ for a redesign of FG to run on MPP systems
> as it gets ever clearer that significant increases in computing
> power have more or less stalled in terms of height (cpu speed) and
> in future, will come instead from width (parallel processing) -
> FG's current design is effectively obsolete]

Yes, it might be time for that. However, the recent work on model loading 
is certainly a step in the right direction.

One problem is to identify parts that we will gain anything from moving to 
a separate thread. I have seen the FDM suggested in the past, but even on 
my (ancient) system JSBSim corresponds to about 1-5% of the CPU usage 
(estimated by looking at the rate sim time progresses in the standalone 
version of JSBSim). Andy has told me YASim is more expensive (it does more 
at runtime) but it is probably at most 20-30% of the CPU usage (guesstimate :).
So, the prospective gains there do not look that large.
Doing some profiling might make the picture clearer.

I think the main targets for parallelization are the rendering pipeline 
and various "add-on" systems, like the traffic manager.
Personally, I'd like to have threads (possibly with very limited 
interaction abilities) available in Nasal for isolated and computation 
intensive tasks (e.g. fast forwarding my fire cellular automaton :).

Just my 2 (euro) cents..


Anders Gidenstam
mail: anders(at)gidenstam.org
WWW: http://www.gidenstam.org/FlightGear/

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