[SciPy-user] ATLAS <--> Building a complete LAPACK library

Nils Wagner nwagner at mecha.uni-stuttgart.de
Tue Mar 26 07:45:08 CST 2002

Robert Kern schrieb:
> On Tue, Mar 26, 2002 at 02:16:12PM +0100, Nils Wagner wrote:
> > Pearu,
> >
> > There is a remarkable change in the size of liblapack.a
> >
> > -rw-r--r--    1 root     root       310528 M?r 26 12:06 liblapack.a
> > -rw-r--r--    1 root     root      5920822 Feb 27 14:26 liblapack.a.old
> >
> > liblapack.a.old (ATLAS3.2.1)
> > liblapack.a (ATLAS3.3.13)
> Aha. There's the problem. ATLAS doesn't provide implementations for
> every LAPACK function. To get a full LAPACK library, you have to follow
> the instructions in ATLAS/doc/LibReadme.txt .
> > Nils
> --
> Robert Kern
> Ruddock House President
> kern at caltech.edu
> "In the fields of hell where the grass grows high
>  Are the graves of dreams allowed to die."
>   -- Richard Harter
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Thank you very much. Finally I have solved my problems.


Building a complete LAPACK library

ATLAS does not provide a full LAPACK library. However, there is a simple
way to get ATLAS to provide its faster LAPACK routines to a full LAPACK
library. ATLAS's
internal routines are distinct from LAPACK's, so it is safe to compile
ATLAS's LAPACK routines directly into a netlib-style LAPACK library.
First, download and install the
standard LAPACK library from the LAPACK homepage. Then, in your
ATLAS/lib/ARCH directory (where you should have a liblapack.a), issue
the following commands: 

  mkdir tmp
  cd tmp
  ar x ../liblapack.a
  cp <your LAPACK path & lib> ../liblapack.a
  ar r ../liblapack.a *.o
  cd ..
  rm -rf tmp

Just linking in ATLAS's liblapack.a first will not get you the best
LAPACK performance, mainly because LAPACK's untuned ILAENV will be used
instead of ATLAS's tuned
one. So, if you use any LAPACK routine that is not provided by ATLAS, it
is essential that you create this hybrid LAPACK/ATLAS library in order
to get the best performance.

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