The following command line shows how you would link the same application with an alternative cblas library libcblas.a,
$ gcc example.o -lgsl -lcblas -lm
For the best performance an optimized platform-specific cblas
library should be used for
-lcblas. The library must conform to
the cblas standard. The atlas package provides a portable
high-performance blas library with a cblas interface. It is
free software and should be installed for any work requiring fast vector
and matrix operations. The following command line will link with the
atlas library and its cblas interface,
$ gcc example.o -lgsl -lcblas -latlas -lm
If the atlas library is installed in a non-standard directory use
-L option to add it to the search path, as described above.
For more information about blas functions see BLAS Support.