[Beowulf] K Computer built for speed, not use
hahn at McMaster.CA
Wed Oct 10 16:31:18 PDT 2012
> Interesting claim. What kind of architecture structure would benefit
> Linpack and would hinder real-world applications?
my guess is they don't like vector.
the quote appears to be from Jun Makino, the GRAPE guy
(so qualifies as "sour grapes!). there is a hint of critique
(which if I read between the lines is saying that for his
kind of astrophysics, he wants accelerator-type architectures,
which differ significantly from vector archs in their relation
of cpu and memory. the "1+3 architectures" table seems to show
a desire for dramatically lower B/F (bytes of memory BW per flop?)
as well as much lower M/F.
as for linpack being a bad benchmark, that's just bullshit.
it's a benchmark. it's not your application. it does a good job
of telling us about a form of performance that is well-understood.
yes, you can make a very good guess at HPL performance if you know
ncpus, peak FP rate and the interconnect performance - but conversely,
a benchmark which is unpredictable is nothing to brag about!
as for the criticism of K's process, well, making sausage is ugly.
everything about a big project is sausage-like, and K is a fairly
remarkable success given the range of issues it had to span.
even ignoring the politics and finance, a sparc chip (!) that does
very wide SIMD, with a memory system to support it, a cooling design
to keep it going, and interconnect to scale.
the only thing that pains me about the whole thing is that I don't guess
all the lessons learned will be propagated or leveraged. mini-K will
not be coming to a center near you. there won't be an commodity chip
that gets "now with added K sauce"...
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