Re: Greased Lightning: ATLAS

[John W. Eaton]

On 19-May-2005, Keith Goodman wrote:

| SSE2
| 
| I removed atlas3-base-dev but not atlas3-base (since some of my
| programs depend on it) and I kept atlas3-headers. I then installed
| atlas3-sse2 and atlas3-sse2-dev. (I'm running debian.)
| 
| When I run "./configure --enable-shared --disable-static" I get "BLAS
| libraries: -lblas". So atlas is not being picked up when I use sse2
| (but it is when I use atlas3).

I don't knwo what is in atlas3-headers, but Octave probably does not
use anything in that package since it provides its own declarations
for blas and lapack functions.  Generally, you need the -dev packages
to build software that uses the corresponding libraries.

| DOES OCTAVE KNOW?
| 
| >From your replies it sounds like I have to get configure right and get
| the LD_LIBRARY_PATH right. Does Octave itself know whether it is using
| atlas? Would it be hard to write a function that returned this sort of
| information so a user could enter, say, 'configuration' at the Octave
| prompt to find out whether or not Octave is using things like atlas?

No, Octave doesn't know what version of blas or lapack it is using.
It only calls the functions through a "standard" interface, so it
doesn't really care.

| BENCH
| 
| Another check would be to run a benchmark. A bench function would be
| useful, if only to make you feel good about all the work you did to
| get atlas working or to feel good about your new computer.
| 
| You can create your own but it is much easier if it is part of Octave.
| 
| I see no reason to use the same bench as matlab. But I would use the
| same interface (input and output format) as matlab.

There have been various benchmark programs for Octave.  But how does
running a benchmark tell you whether you are using a fast
implementation of blas or lapack on your system if you only have one
data point?

jwe



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