Java and Multi-Processor Systems

[This may be the wrong form, please point me to the correct one if I should redirect this!]
Is it possible to use Java in a multiprocessing environment where Java can take advantage of the multiple processors? Naturally Threads are the obvious parallel mechanism, but I suspect there are others.
Motivation: Basically we are trying to build an inexpensive system to do scientific and mathematical computing where the runs can take hours or days on traditional uniprocessor systems. Presumably a multiprocessor system would be the first stop, although Grid computing may be as effective.
So any pointers for doing cpu intensive programming with Java would be appreciated!

You need to have atleast one active thread per CPU.The domain I am looking at is "Agent Based Modeling" (ABM). In that sphere, each agent is fairly independent of all the others, making decisions based on "local knowledge". Our current simulation uses 35,000 agents.
You may find that different architecture may limit
the number of processors you can effectively exploit
but you should be able to use2-4 CPUs without
signifciant trouble.I'm not clear on how I can ask Java to use the multiprocessors I may have in my system. Do I simply assign a thread to each agent? That would be quite easy to do.
So I think the question here is: Does Java assign threads to multiprocessors? Does it need a special compile/run flag to do so? Do I need to include special Java code to somehow promote this behavior?
If the processing is really CPU intensive the best
option may be to find the bottlenecks with a profiler
and write them in C. You should be able to get a
significant speed up this way with minimal
conversion.That may be necessary, but in the ABM space, people are leaving C for Java due to its being fast enough and the networking support, memory management, etc just too nice to pass up!
To use multiple threads you need to be able to
exploit a natural parrellism in the work you are
doing. If the task is genuinely single threaded you
wil only every be able to use one CPU.This should be easy, see above .. due to each agent being reasonably independent.
Thanks for the thoughtful response!

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Jim Ewing wrote:
>
In general, is it better to run Weblogic on a fast single processor system
or on a multi-processor system where the individual cpus are less powerful?
I am assuming that the platforms are WINTEL and all other things (memory,
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>
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Message was edited by: JeongEog IM
Message was edited by: JeongEog IM

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Ola Ramiro,
como estas?
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brahim wrote:
Dear readers,
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>
I consider WebLogic to be a great no-nonsense J2EE implementation (not
counting class loaders ;-).Look for major improvements in that area in version 6.0.
Thanks,
Michael
Michael Girdley
BEA Systems Inc
"Cameron Purdy" <[email protected]> wrote in message
news:[email protected]...
Rob,
I consider WebLogic to be a great no-nonsense J2EE implementation (not
counting class loaders ;-). Gemstone's architecture is quite elaboratewhen
compared to WebLogic, and BTW they spare no opportunity to compare to
WebLogic although never by name. (Read their white paper on scalabilityto
see what I mean.) I am quite impressed by their architecture; it appearsto
be set up for dynamic reconfiguration of many-tier processing. Forexample,
where WL coalesces (i.e. pass by ref if possible), Gemstone will always
distribute if possible, creating a "path" through (e.g.) 7 levels of JVMs
(each level having a dynamic number of JVMs available in a pool) and if
there is a problem at any level, the request gets re-routed (full failover
apparently). I would say that they are set up quite well to solve the
travelling salesperson problem ... you could probably implement aweb-driven
neural net on their architecture. (I've never used the Gemstone product,
but I've read about everything that they published on it.) I would assume
that for certain types of scaling problems, the Gemstone architecturewould
work very very well. I would also guess that there are latency issues and
administration nightmares, but I've had the latter with every app server
that I've ever used, so ... $.02.
Cameron Purdy
[email protected]
http://www.tangosol.com
WebLogic Consulting Available
"Rob Woollen" <[email protected]> wrote in message
news:[email protected]...
Dimitri Rakitine wrote:
Hrm. Gemstone reasons are somewhat different.I'm not a Gemstone expert, but I believe their architecture is quite
different from a WebLogic cluster. Different architectures might have
different trade-offs.
However, out of curiosity, what are their reasons?
Anyway, here is my question:
why running multiple instances of WL is more efficient than running
one
with
high execute thread count?The usual reason is that most garbage collectors suspend all of the jvm
threads. Using multiple WLS instances causes the pauses to be
staggered. Newer java vms offere incremental collectors as an option so
this may no longer as big of an issue.
-- Rob
>

Java and Multi-Processor Systems

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