MATLAB Release Notes

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:

• 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
  

Platform Limitations

Upgrading from an Earlier Release