I'm not an expert (you've heard that a few times, eh?), but my understanding is
that the best case goes as N*ln(N), and worst case the thing degenerates to
full blown N-body code running at N**2 performance.
Also, I think it depends an what you're running, but a 10^4 particle simulation
could take a while on a Sparc. I'll have to talk to a fellow grad student to
get the specifics, but there's a treecode used here to simulate compact galaxy
clusters (~5 galaxies) which can take several days to get a merger or
non-merging result. I'll have to find out more, as this is not an appropriate
A point of interest: Treecodes can be highly efficient when vectorized and run
on a parallel machine. I am told that one of the above cD cluster simulations
which takes ~week on an HP735 has been run on IU's new Intel Paragon MPP
machine (64 nodes), taking 9 hours.
> 3) How do folks visualize the output of these simulations (I'm
>X-windows based, so I guess the question should be read with this in
>mind). In this case I think I can solve this problem with tools I
>already know about. But again it's stupid to screw around with
>something that's not quite right if the "right tool for the job" is
>sitting out there somewhere on an ftp site.
Another grad student here has been working on visualization of these cluster
simulations. The product used is called AVS (X11 based), and through the use
of scripts, NFS mounting of an enormous amount of disk space and much patience,
video movies of these simulations are made with support from IU's CICA (Center
for Innovative Computing Applications). Keep your eyes open, as you may see
these in the near future. Also, for a preview of an MPEG of one of these
simulations, check out http://enif.astro.indiana.edu, the IU Astro WWW server.
-- Shawn Slavin Indiana University Astronomy