[Beowulf] Re: building a new cluster

[SC Huang]

--- Joachim Worringen <joachim at ccrl-nece.de> wrote:

> SC Huang wrote:
> > 5. I only have wall-clocking timing of my code on various
> platforms. I 
> > don't know how sensitive it is to cache size. I guess the bigger
> cache, 
> > the better, because the code is operating large arrays all the
> time.
> 
> If your arrays are really large, than it's the memory bandwidth that 
> counts, not the cache size. Or your ability to implement
> cache-friendly 
> (blocked) versions of your code (probably with the assistance of 
> libraries like ATLAS).


The arrays are large, but I have made "continous memory access" as much
as I can. So cache reuse should be ok. I once tested this using a Cray
compiler. The "cache miss" ratio seemed reasonable.



> Just a side note on this: we have a 32-node dual-Athlon cluster with 
> Myrinet in the lab as well as an SX-6i (single processor SX-6). We've
> 
> seen our financial modelling codes run faster on the SX-6i than on
> the 
> cluster (with a non-trivially parallized version). And in contrast to
> 
> the cluster, the SX-6i is running non-stop for months (as long as we 
> have it here). It's much smaller and more energy-efficient, too - but
> 
> it's not cheaper.


Thank you for the comments. Is SX-6 a shared memory machine? May I ask
how many processors were used when it ran faster then the cluster? Just
curious. Thanks.



> 
>   Joachim
> 
> -- 
> Joachim Worringen - NEC C&C research lab St.Augustin
> fon +49-2241-9252.20 - fax .99 - http://www.ccrl-nece.de
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