The BLAS (Basic Linear Algebra Subprograms) are routines that provide
standard building blocks for performing basic vector and matrix
operations. The Level 1 BLAS perform scalar, vector and vector-vector
operations, the Level 2 BLAS perform matrix-vector operations, and
the Level 3 BLAS perform matrix-matrix operations. Because the BLAS
are efficient, portable, and widely available, they are commonly used
in the development of high quality linear algebra software, LAPACK
for example.