README.blas

Oct 1, 2015

SPRNT uses BLAS for certain low-level vector options. One of the linear solvers, UMFPACK,
uses BLAS dgemm routine for matrix vector multiplication. By default, system-wide static
BLAS installation will be used (usually /usr/lib/libblas.a). The choise of default BLAS
library can be overwritten by specifying variable BLAS_LIB during configure. For example,
if a customer BLAS library /usr/local/lib/libmyblas.a should be used, the configure
should be:

./configure BLAS_LIB="-L/usr/local/lib -lmyblas"

If ATLAS should be used, the configure script should be called as:

./configure BLAS_LIB="-L/usr/local/atlas/lib -lf77blas -lcblas -latlas -lgfortran"

Caveats:
1. The location of the library should be provided as the absolute path. Relative path
   is not going to work.
2. The BLAS library (or its equivalent) should be built as positition independent 
   (i.e., with -fPIC flag for gcc)