# [Beowulf] Physics Problems for Beowulf

Joe Landman landman at scalableinformatics.com
Tue Feb 21 08:52:18 EST 2006

```Hi Timo:

Timo Mechler wrote:
> Hello all,
>
> Over the past couple years I have done research one Beowulf clusters and
> also implemented the first one at my school.  Now that I'm getting closer
> to graduating, I'm looking of turning all this work into a senior project.
>  The only part that's missing though, is a good physics problem that I
> could code up a numerical solution for and run in parallel.  I have done
> some of this, but it's mostly been simple stuff, such as a simple
> numerical integration via the Monte Carlo method in parallel.  I know some
> of you on this list are professors and professionals that have extensive
> physics knowledge.  What sorts of physics problems would you suggest I
> might be able to code up that would take a some time run on a Beowulf
> cluster?  I'm going to be using Fortran 77 with MPI libraries as my base
> for coding.  Thanks in advance for your help on this, I appreciate it.

A problem I coded up for a class I teach on HPC applications is an ideal
gas in a 2D box, with correct (momentum conserving, energy conserving)
dynamics.  It was done in C though.  I might suggest something like
this.  Then you can measure pressure (number of impacts on perimeter
wall per time step), temperature, and volume, and do experiments where
you suddenly double the volume, or have one of the wall boundaries start
creeping downwards to decrease the volume, or chill the walls, so that
upon collisions with the walls the atoms get slower/faster (lose/gain KE
to/from the reserviour).

I did this as an example that I wanted them to add in how to move atoms
between processors (no periodic BCs, just "partitions" that atoms can
cross.  And if they cross it, you need to move them to the adjacent
processor.

I have done up to about 1 million "atoms" on a 32 way run, and it works
pretty nicely.  Somewhat hard to visualize the output, so I had it write
stuff out in ".xyz" format, and used VMD to generate a movie.  You can
see it (about 100 atoms, tiny interaction radius, and a few thousand
steps) here at http://www.scalableinformatics.com/public/idealgas.mpg .

Joe

>
> Best Regards,
>
> -Timo Mechler
>
>

--
Joseph Landman, Ph.D
Founder and CEO
Scalable Informatics LLC,
email: landman at scalableinformatics.com
web  : http://www.scalableinformatics.com
phone: +1 734 786 8423
fax  : +1 734 786 8452
cell : +1 734 612 4615
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