===== BLAS/LAPACK =====

BLAS stands for Basic Linear Algebra Subprograms.

This library contains linear algebraic operations that include matrixes and vectors. Its functions are separated into three parts:
  * Level 1 routines to represent vectors and vector/vector operations.
  * Level 2 routines to represent matrixes and matrix/vector operations.
  * Level 3 routines mainly for matrix/matrix operations.
This library is included in the Intel MKL package.

==== LAPACK ====
LAPACK stands for Linear Algebra PACKage.
This is a set of **Fortran 77** routines used to resolve linear algebra problems such as the resolution of linear systems, eigenvalue computations, matrix computations, etc. However, it
is not written for a parallel architecture.

This library is included in the Intel MKL package.

==== BLACS ====
BLACS stands for Basic Linear Algebra Communication Subprograms.
BLACS is a specialized communications library (using message passing). After defining a process chart, it exchanges vectors, matrices and blocks and so on. It can be compiled on
top of **MPI** or **PVM** systems.

==== TIPS ====

=== Ubuntu ===
To switch between different installed BLAS/LAPACK implementations (ATLAS/GOTO/Open) or to fix the links in **''/usr/lib''** you can use this:

<code bash>update-alternatives --config libblas.so.3gf</code>

<code bash>update-alternatives --config liblapack.so.3gf</code>

Make sure you select for BLAS and LAPACK the same Implementation, don't mix ATLAS and OpenBLAS!

== Possible Errors ==
If you encounter an error like: **''update-alternatives: error: no alternatives for liblapack.so.3gf''** then try first:
<code bash>update-alternatives  --config liblapack.so.3</code>

If you encounter an error like: **''update-alternatives: error: no alternatives for libblas.so.3gf''** then try first:
<code bash>update-alternatives --config libblas.so.3</code>