Re: octave + mkl

[Jordi Gutiérrez Hermoso]

On 16 May 2012 17:55, Joshua Dillon <address@hidden> wrote:
> Sorry I didn't intend to start a fight.  ...Just thought "It was
> useful to me and may be useful to others."

Right, what would be far more useful to others in the long run is if
we could figure out what sort of computatons MKL is performing and
implementing similar ones in LAPACK, FFTW, OpenBLAS, ATLAS or another
free BLAS, instead of promoting non-free software and opaque magic.

Can you help us with that?

What is MKL doing? Which BLAS were you comparing with MKL? Is MKL
parallelising better? Do you see all of your cores being used better
with MKL? Is it using hardware instructions better on the Intel
hardware? If you try it on AMD hardware, is MKL also deliberately
pessimising like icc does, or do you also see an improvement?

Are you really seeing drastically better performance with eigs? All of
the heavy lifting in eigs is done in ARPACK, and off the top of my
head, it shouldn't make too much of a difference which BLAS you're
using, although of course there are BLAS calls in ARPACK.

There is a parallel version that uses OpenMPI, PARPACK. Are you seeing
much of an improvement with that one? I can't recall right now if
PARRPACK is a complete drop-in replacement or if we would have to
modify liboctave/eigs-base.cc in Octave to make use of the parallel
version. There's also the issue that I'm not sure if OpenMPI can work
easily on a single multicore box.

I do hope Google hasn't tried to quell the rebellious and playful
hacker in you and you can still dedicate some of your 20% to these
interesting questions. :-)

TIA,
- Jordi G. H.