[FRIAM] deployable and open source ABMs

[Douglas Roberts]

Hi, Marcus.

I'm presently involved in discussions of the technical issues of building
ABMs in Java for HPC computing environments in another arena. However, I
suspect that when are talking about deploying Tamarin projects, we are not
talking about deploying them on Teragrid resources or (just) on HPC Linux
clusters.

HPC brings several of Java's performance characteristics into the spotlight
when considering it as the implementation language for distributed memory
ABM simulations.  Here are a few of those issues:


   1. There are no supported sophisticated message passing toolkits, such
   as mpi,  that would allow the Java developer to take full advantage of a
   message passing HPC platform.  Mpi provides the HPC developer with a large
   collection of message passing functions: broadcast, scatter/gather,
   blocking/non-blocking sends, message data serialization, etc..  None of
   these tools are available to the pure Java developer.
   2. Similarly, there are few, if any Java support packages that would
   allow the Java developer to utilize high speed interconnect frameworks, such
   as Myrinet and Infiniband on distributed HPC platforms.  Message passing
   operations in a Java-based application, therefore, will be many times slower
   than those implemented in a language environment better suited to HPC.
   3. Java's performance, because of it's garbage collection design, will
   always be inferior to that of C, Fortran, or C++, which, as you point out,
   are the languages of choice for HPC implementations.
   4. Java cannot be optimized to any specific HPC platform as
   efficiently as is possible with the above-mentioned languages, because the
   HPC language compilers usually are optimized for the specific platform that
   they are installed on.   This introduces yet another performance penalty for
   the Java application.

Add them all up, and the performance penalty for pure Java HPC applications
is huge.

--Doug
-- 
Doug Roberts, RTI International
droberts at rti.org
doug at parrot-farm.net
505-455-7333 - Office
505-670-8195 - Cell


On 11/25/06, Marcus G. Daniels <mgd at santafe.edu> wrote:
>
> Hi Doug,
> > I guess we need a definition of "good performance" here.  Languages
> > with garbage collectors are not known for exceptional performance.
> Well, I am in the camp that use C variants are best for serious
> simulation as it factors out the uncertainties of garbage collection and
> bytecodes interpreters/JITs.  But, given that Java is so popular, and
> that a common (but shallow) motive for its use is to make it easy to
> show customers simulations, then the possibility of a truly dynamic
> language that is embedded in a browser seems like an interesting step
> forward for demos or small scale simulations.
>
> cheers,
>
> Marcus
>
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