[Beowulf] Threaded code
hahn at physics.mcmaster.ca
Tue Aug 17 09:16:59 PDT 2004
> 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
yes. I didn't read its optimizer or its ncpus-detection code,
but this is completely in line with the whole point of atlas,
which is to tune the library to suit the particular configuration.
> effectively render binary RPMs of Atlas completely useless? Would also
no, just very specific. for instance, you certainly shouldn't run Atlas
on a machine which has caches of different size than the library was built
> make building static binaries (don't know if it is possible with Atlas
> libs) a waste of time if you need a portable binary.
Atlas is inherently non-portable, at least non-portable to machines
which have different configuration.
I think this is different from fftw, which at runtime dynamically
generates a semi-optimal strategy of combining precompiled units.
if Atlas did this, it would need to compile code blocked for a whole
range of cache sizes, for instance. possible, but I don't believe
it does that. naively, it could simply parameterize for NTHREADS,
but that would probably give trouble on machines which have shared cache,
in which NTHREADS would interact with blocking...
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