[Beowulf] Vector coprocessors

Daniel Pfenniger daniel.pfenniger at obs.unige.ch
Thu Mar 16 12:32:13 EST 2006



Jim Lux wrote:
...
> There are probably applications where a dedicated card can blow the 
> doors off a collection of PCs.  At some point, the interprocessor 
> communication latency inherent in any sort of cabling between processors 
> would start to dominate.

As usual it depends on the applications. Vector computations
are not universal, even if frequent in technical problems.
In the favorable cases it is not rare to have say over 10% serial
code that does not benefit from the card.  In the end the card, despite its
192 procs, may just accelerate typical applications by a factor a few.

>> If Clearspeed would consider mass production with a cost like 
>> $100.-$500.-
>> per card the market would be huge, because the card would be competing 
>> with
>> multi-core processors like the IBM-Sony Cell.
> 
> You need "really big" volumes to get there. 

Yes, but it does not seem to me unreasonable to put such a card in
millions of PC's if the average applications run a bit faster and the
cost increase stays below the PC cost.  After all
the 8087 math coprocessor of the i386 era did just that.

....
> 
> I would say that there is more potential for a clever soul to reprogram 
> the guts of Matlab, etc., to transparently share the work across 
> multiple machines.  I think that's in the back of the mind of MS, as 
> they move toward a services environment and .NET

Lots of people have thought about that for a long time, including
Cleve Moeller.   The potential clever soul should be well above
average, and considering MS products, well above MS average programmer.

An intriguing way to parallelize C with threads on multicore processors is
provided by Cilk (http://supertech.lcs.mit.edu/cilk/).  Cilk consists of
a couple of simple extensions to the C language.

If anyone has experience with Cilk it would be nice to share.

	Dan



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