Dear Marcus,
I really appreciate for your comments.
As my understanding, you claimed that message passing is not good for
SWARM
mainly because communication overhead between agents might be nontrivial.
Right ? But, for example, (1) if models perform considerable amount of
computation in a single
simulation phase (or cycle) with minimum communication between agents
(2) if the size and/or scalability of simulation models is much important
than performance (or execution time)
do you still think multi-threading approach is better than message
passing
because of the nature of SWARM even in above cases ?
Also, could you give me some information (or link) on SWARM
models/projects
that are already done or planned for 'large-scale' simulation ?
For example, is there any SWARM project that uses more than 256 (or 512)
nodes in MPP machines ?
Sincerely,
Sunwoo
From: "Marcus G. Daniels" <address@hidden>
Reply-To: address@hidden
Date: Thu, 29 Jan 2004 10:44:46 -0700
To: address@hidden
Subject: Re: [Swarm-Modelling] SWARM on Clusters
Sunwoo Park wrote:
I just joined in this mailing list.
I have a simple question regarding SWARM software.
Is there any SWARM implementation that runs on cluster machines (or MPP
machines) based on Message Passing Paradigm (e.g., MPI) ?
Swarm has a fine-grained knowledge of concurrency during a simulation.
When multiple agents do something at the same timestep, Swarm knows
this. But that's just a little atom of the whole simulation execution
sequence. What this means is that in order for Swarm to exploit this
knowledge on a parallel computer, it is necessary to be able to
efficiently get that atom of computation to a physical processor. A
cluster, like a Beowulf arrangement of PCs, can't do this because the
communication expense of getting the atom to the processor not amortized
by the computation done. A SMP or NUMA system can do this because the
communication/overhead expense of getting the computation to the
processor is small. So if you have a two or four or eight way Opteron
or Sun system or a big NUMA system like a SGI Altix, the interconnect
between processors could reasonably slurp up these atoms and there would
be a scalability win.
I think it would be hard to make a message passing system scale very
well based on an architecture like Swarm. You'd need low-latency
interconnect, maybe Myrinet.
In any case, Swarm doesn't implement either. A multithreaded Swarm
would be feasible, but would assume a shared memory system like I
mentioned.
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