User`s guide

2 MATLAB 6.1 Release Notes
2-22
You May Need to Overwrite the MATLAB Default
Choice of BLAS
On the PC, under both Linux and Windows operating systems, MATLAB
determines at startup time what processor your computer has, for example
Genuine Intel Pentium II, Pentium III, or AMD Athlon. MATLAB then
automatically selects the most appropriate BLAS for your processor. The same
is true on the SUN, where MATLAB distinguishes between UltraSPARCs and
non-Ultra machines.
However, on the remaining platforms you get the default BLAS, which is
usually targeted for a reasonably modern or common processor. Namely:
•ALPHA 21264
•HP700 PA-RISC1.1
•HPUX PA-RISC2.0
•IBM_RS Power3
•SGI R12000
If you have reason to believe that your processor is closer to another of the
flavors of BLAS distributed with MATLAB, for example 21164 on the ALPHA
or PA-RISC2.0 on the HP700, you might want to override the default choice of
BLAS. Look in your
<MATLAB>/bin/$ARCH directory for libraries beginning with
atlas_ to see your options.
Overriding the Default
The way to override the default choice is to set the environment variable
BLAS_VERSION before invoking MATLAB. For example (in csh)
setenv BLAS_VERSION atlas_21164.so
setenv LAPACK_VERBOSITY 1
matlab
The environment variable LAPACK_VERBOSITY simply confirms that your choice
of BLAS is being loaded once you start up MATLAB.
Restoring the Default
If you would like to return to using the default provided by MATLAB, you may
use the command (in
csh)
unsetenv BLAS_VERSION