It provides a mature open source implementation of BLAS APIs for C and FORTRAN 77.

ATLAS is often recommended as a way to automatically generate an optimized BLAS library.

ATLAS runs on most Unix-like operating systems and on Microsoft Windows (using Cygwin).

It is released under a BSD-style license without advertising clause, and many well-known mathematics applications including MATLAB, Mathematica, Scilab, SageMath, and some builds of GNU Octave may use it.

If so, If not, The actual decision is made through a simple heuristic which checks for "skinny cases".

The high level choose an order to traverse the blocks: ijk, jik, ikj, jki, kij, kji.

For jik the ideal situation would be to copy A and the NB wide panel of B.

Choosing the bigger of M or N for the outer loop reduces the footprint of the copy.

(If that fails it uses the no-copy version of GEMM, but this case is unlikely for reasonable choices of cache edge.)

Installing ATLAS on a particular platform is a challenging process which is typically done by a system vendor or a local expert and made available to a wider audience.

For many systems, architectural default parameters are available; these are essentially saved searches plus the results of hand tuning.