The June Minor
Review meeting features two presentations from the Platform
Competence Centre.
Andrzej Nowak presented 'Scalability
Tests of a Multithreaded Geant4 Prototype'. He started by
describing the scalability results on a 24 core Dunnington
server where he saw reasonable scaling up to 8 cores but rather
disappointing scaling beyond that point. The investigations of
the causes have been done in multiple stages and Andrzej
described the various efforts in detail. Several new tools were
developed and the Intel Threading tools needed patches since MT
Geant4 is a large and complex package. He concluded by saying
that the locking of the Ion Table in Geant4 is now seen as the
main culprit and discussions are underway with the authors of
the multithreading prototype to decide the next steps.
Sverre Jarp described the “Larrabee
New Instructions”. “Larrabee” is a new development from
Intel. It is used to describe both an architectural extension of
x86 (basically with a Vector Unit) and also the graphics chip
(based on the architecture) that Intel will commercialize within
the not too distant future. The chip will be a “many-core”
implementation which will also feature 4 threads per core.
Sverre described the architecture and the large instruction set
that comes with the vector unit. As many as 32 vector registers
and 8 mask registers are present for use by the vector
instructions. He stated that the combination of advanced memory
instructions, such as gather/scatter, plus a sophisticated use
of masking, could lead to very efficient algorithmic
programming. He concluded by predicting that Larrabee can appeal
to programs that exhibit either data or task parallelism, but
that we need to understand Intel’s plans for a software
environment for the chip before the next steps can be taken.
Mélissa Le Jeune reviewed the list of
publications/presentations since May. She also outlined the
plans for a newsletter that will appear after each Major review
meeting.
Next CERN openlab Minor Review Meeting will be hold on 8
September
2009.
Sverre Jarp, CERN openlab
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