[Beowulf] Is there really a need for Exascale?

Alan Louis Scheinine alscheinine at tuffmail.us
Thu Nov 29 09:11:39 PST 2012

I would like to point-out that
The Opportunities and Challenges of Exascale Computing
has some interesting information in the section "The Hardware Challenges"
Less recent (2008) but much more interesting with regard to hardware is
ExaScale Computing Study: Technology Challenges in
Achieving Exascale Systems, Peter Kogge, Editor & Study Lead
The 2008 report convinced me that a large amount of hardware
improvements are needed so I've remained curious as to whether
the changes would come to pass from commercial mass-market COTS

A useful collection of reports can be found at

To clarify, I'm not recommending the use of cell-phone computers,
rather, for a question after talk I asked a knowledgable person in
the field of exascale what was currectly driving technological
advances towards Exascale hardware and he indicated that circuit
improvements for cell phones would drive the low-power circuit
development.  Personally, I'm not convinced.

With regard to attracting government funding, many of the reports
such as "The Opportunities and Challenges of Exascale Computing"
seem to be primarily sales brochures oriented towards that goal, IMHO.

With regard to cache coherency, Eugen Leitl wrote "There also cannot
be any such thing as a global memory, unless you want it to be slow
and spend a lot of silicon real estate to make multiple writes
to the same location consistent."  It is a very interesting question
as to what can be done with global shared memory without requiring
coherency.  For some algorithms global atomic operations are needed
but not necessarily cache coherence.  Supercomputer manufacturers
are building ever more sophisticated networks, on the other hand,
one of my interests in the Beowulf mailing list is to hear about
global memory improvements available with COTS hardware so
researchers are not dependent on the few supercomputers with
specialized interconnect hardware.



  Alan Scheinine
  200 Georgann Dr., Apt. E6
  Vicksburg, MS  39180

  Email: alscheinine at tuffmail.us
  Mobile phone: 225 288 4176


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