Re: address@hidden: address@hidden: [lists.hpcoders.com.au: Re: [Swarm-Support] development priorities (was Re: Membership in Swarm Developmen Group)]]]

[Marcus G. Daniels]

Russell Standish wrote:
> Porting to 64 bit should not be hard. EcoLab has always been 64 bit
> clean due to a requirement to run on whatever supercomputer I had
> access to. 
Swarm has some more complicated problems due to the need to call methods 
with mixed argument types.  
It unfortunately needs to know about the ABI of the machine.   It's an 
OS by OS issue.  

But, it's also kind of neat, once you've got it because then you can 
take apart a C calls and resubmit them to other language/application 
environments or machines.  Very lightweight infrastructure for remote 
procedure calls.

Concerning the Cell:
> I'm sceptical of this. The subprocessors (as I understand it)
> effectively act as a vector processor, and vector processors are
> rarely useful in ABMs. A better target would be to ensure Swarm runs
> on the dual core (or just one of the cores is threading is not
> feasible - has OpenMP been implemented for Objective C yet?). This
> shouldn't be hard, of the same magnitude as the 64 bit port, assuming
> access to hardware. The ABMers with peculiar requirements (eg linear
> algebra, or neural networks say) can then link to a Cell optimised
> library that is outside of Swarm.
>   
I've looked at it in some detail.   Cell SPUs don't have fancy 
out-of-order execution features and big caches, true. You do have to 
tune code for them to get high performance, but they are most definitely 
CPUs, and not just vector units (they do have vector units).   Normal C 
or C++ or Objective C will compile for them.   The Barcelona 
supercomputing facility distributes a full cross compiler suite with 
source code and IBM has a free simulator to watch every thing happen at 
the physical level.    It's pretty cool stuff.  I was skeptical as well, 
but soon expect to be the proud owner of my own PS3.  I don't play video 
games, I just will use the thing as a PC and number cruncher!

Meanwhile, IBM is working on their Octopiler which will implement OpenMP.

The idea of targeting Swarm (or some new or old message-oriented ABM 
toolkit) to the Cell is a motivated by the fact that scalability of 
Swarm (like over MPI or using RMI) is limited by the slow links between 
nodes.   Swarm is supposed to be fine-grained discrete event 
simulation.  But the Cell has huge DMA bandwidth and ~5 nanosecond 
latency.   It should be possible to message from the PPU to the SPU no 
problem.   I've done some experiments where literally thousands of RPC 
messages can be queued or in flight without any real slow down.  

P.S. I remember you once mentioning your smart pointer system in 
EcoLab.  Is there a paper handy?  
Maybe I'm an old-timer but I'm glad there are still C and C++ ABM 
simulators out there!