[Beowulf] Threaded code
camm at enhanced.com
Tue Aug 17 09:48:40 PDT 2004
In this regard, Debian has an intermediate atlas strategy. Large
performance gains are attempted to be covered by distributed
precompiled binaries, the optimal version of which is automatically
loaded at runtime. Smaller gains are left up to the user to custom
compile the package -- a convenient mechanism for this is provided.
There is currently a large base of software shipped with Debian which
can thus take advantage of atlas-supplied performance gains
dynamically at runtime, i.e. without recompilation.
Joe Landman <landman at scalableinformatics.com> writes:
> Mark Hahn wrote:
> >>variables? (do you have an NCPU=1 or something like that hanging around?)
> >afaikt, when threads are enabled, atlas compiles in the number of threads,
> >based on what it detects on the machine doing the compilation. so, for
> >instance, if you happened to compile atlas on this machine with the uni
> >kernel, (or some other uni) you'd get no threads. this is a bit
> >counterintuitive to anyone used to OMP_NUM_THREADS, but it certainly
> >makes sense for atlas.
> Ok, I haven't used atlas in a while. Are you saying that it hardcodes
> the number of processors into the code itself? Wouldn't this
> effectively render binary RPMs of Atlas completely useless? Would
> also make building static binaries (don't know if it is possible with
> Atlas libs) a waste of time if you need a portable binary.
> >> Are you sure you are using only one CPU (e.g. what tests are you
> >> using that indicate a single CPU)?
> >yes, another good question. if you simply don't get any speedup from using
> >threads, it doesn't necessarily imply that you're not using threads ;)
> I have had codes that spent very little time in the parallel sections
> in the past. Simply adding another processor/thread does not
> automagically half the run-time. You would need to use some of the
> more advanced query tools to see what is going on.
> >regards, mark hahn.
> Joseph Landman, Ph.D
> Founder and CEO
> Scalable Informatics LLC,
> email: landman at scalableinformatics.com
> web : http://www.scalableinformatics.com
> phone: +1 734 612 4615
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Camm Maguire camm at enhanced.com
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