Hi Brian,

On Mon, 2010-05-17 at 11:31 -0700, Brian Gerkey wrote:
> I agree with your analysis.

OK, sorry if I was being dense ;) I guess my point was that after a
while the code currently in SVN will also peg a single core completely.
Of course, that doesn't solve the problem.

> The practical issue with the patch is that, even a moderate value of N
> (I've been testing with the default, N=30) entails a constant
> computational load exceeding what a single 3GHz core can do.

Yeah, I guess it's OK for offline processing of logged data, though.

> I think that the constant-time update is the way to go, but that it
> will be hard to use without also multi-threading the filter update
> step in GMapping.

Such that subsets of the particle set would be processed by different
threads? I've thought about that. It should be fairly straight forward
to implement.

The other thing one could do is to run GMapping through a profiler and
optimize critical code paths. Eye-balling may also help. I've only had 
a quick look at the code, but there's some low hanging fruit in
registerScan() that might cut computation time significantly if
optimized.

Both would be fun projects to work on but I cannot currently devote time
to either of them. I should be able to get back to this in a few weeks
from now, though.

Cheers,

Rene

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Dipl.-Inf. René Wagner                     Junior Researcher
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