[Beowulf] Stroustrup regarding multicore

Lux, James P james.p.lux at jpl.nasa.gov
Wed Sep 3 13:22:12 EDT 2008


I would say that the single biggest problem in HPC today is not getting
sufficient hardware horsepower, but in effectively using that power.  10
years ago, just getting a cluster going was a bit of a challenge, in terms
of knowing what hardware to get, how to interconnect it, etc, but now, a lot
of that is cookbook (or available turnkey from a variety of vendors... A
very different matter from when Sterling, et al wrote their book back in
98/99). Sure, there are still hardware issues that are worthy of discussion
on this list (details of interconnects, etc.), but one doesn¹t see the
discussions about topologies that one saw back then.  The hardware is now to
the point where you rack up the computers, hook them all to a very fast
switch with huge bisection bandwidth, and you¹re done.

However, the topic of taking a simple problem and effectively parallelizing
it (either at a EP level as can be done with some Monte Carlo or systematic
simulations, or at a fine grained level, as with matrix numerical modeling)
is very much grist for the mill.

After all, what are all those folks building parallelizing/vectorizing
compilers trying to do but reduce the substantial software
engineering/design problem, so that a scientist or engineer can just write
their problem out in simple form, and have ³the backend² figure out how to
do it efficiently (or at all).

There are many problems which are, by their nature, software design complex
enough that it is not reasonable to have the person ³asking the question²
also be knowledgeable enough to manage the substantial software development
project. This would be true, if for no other reason than managing a software
development effort takes a different skill set than asking good science or
engineering questions.

So, the real challenge facing builders (in the larger sense) of Beowulfs is
in developing methods to get the work actually done, and if that requires
developing skills in ³eliciting requirements² or, more probably,
³communicating between software speak and science speak², then this is an
appropriate place to do it (if not here, then where *would* be a place where
it¹s more germane.. I can't think of one off hand)

It's sort of like our discussions about communicating with the facilities
folks about power requirements or HVAC.  Someone building a cluster needs to
know something about this to be an intelligent consumer, but nobody expects
the scientist to be down there sweating copper pipes for the chiller or
cabling up the EPO button for the UPS.

The list is valuable because there *are* folks here who do know how to sweat
pipes, manage software projects, and interpret the electrical code, and you
can ask a question about such things and get a host of responses, some more
useful than others.

Jim


On 9/3/08 9:10 AM, "Prentice Bisbal" <prentice at ias.edu> wrote:

> This discussion is still completely off-topic. This is a list about
> computing issues relating to beowulf clusters, not software engineering
> at large, sociology or psychology.
>
>
>


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