[simspark-devel] SimSpark boosting project

[Sander v. D. <sgv...@gm...>]

Hello MC,

As you may know, the RC federation put out a call for proposals for
projects, among others to work on the competition infrastructure. I sent in
a proposal together with Ubbo Visser, which got accepted. So now I am with
Ubbo to work on simspark for 2 months, and I would like to keep you up to
date with what we're doing.

The main aim of our project is to make the simulator usable for bulk
training. One part of that means debugging the simulator and make it faster
and more stable, the other part is to make some external tools. On the
second point we are still working out the details, but on the first part I
did some work:

* Did a lot of profiling, which a.o. showed that the server spent more than
10% of the time on dynamic casting alone. This was mostly because of
continuous searches for nodes in the scene tree. I have put in some caching
here to alleviate it, reducing the time spent casting to 1%. This extra 10%
has now gone to ODE. I still have to create some performance tests to see if
this made stuff faster.

* Multi threading mode is fixed (but see below). Although at first I was
doubtful of whether the current way it is done would help, it should,
because now the second and third most costly things, gathering perception
data (20%) and gathering monitor data (8%) can now be done in parallel.
However, while running a 6vs6 game there is not a real noticeable speed-up.
But again, I still have to do proper performance tests to see what it does.

However, the biggest opportunity to optimise is ODE, which now eats up
67-70% of all computation time. There was a project at CMU in 2007 to
parallelize ODE [1], where they made the collision detection parallel.
Profiling shows however that this will not help: collision detection takes
up 0.45% in rcssserver3d. What is expensive for us, is stepping the physics.
Luckily, ODE already splits this work into different parts, updating
'islands' seperately, where in our case each island is one agent. I am now
working on parallelising this, and if that works we can in theory cut up the
67% CPU time into 12/18 parts (4vs6/9vs9) that can be run in parallel,
hopefully making having 8 cores actually useful.

So far about what I am doing. Now, I would also like something from you guys
;-) First of all, give the new stuff I committed a good test. Behaviour of
the simulator should still be the same, but it could be that I missed
something and that timing of messages is slightly different, breaking
agents. Also, give the multi threaded mode a good test, see if you can make
it crash. And, finally, I will be working full time on the simulator for 1
1/2 months more, if you think there is anything that I may be able to
squeeze in there, do let me know!

Cheers,
Sander

[1] http://www.cs.cmu.edu/~mpa/ode/

-- 
Adaptive Systems Research Group
Department of Computer Science
University of Hertfordshire
United Kingdom