BLAS is a set of functions for basic linear algebra operations. Vendors often supply BLAS libraries optimized for their hardware. A large portion of the computational engine in COMSOL Multiphysics relies on BLAS. Included with COMSOL Multiphysics is the Intel® oneAPI Math Kernel Library (oneMKL) BLAS library, which is the default BLAS library for Intel and AMD processors. For AMD® processors with the Zen architecture, COMSOL provides the AMD Optimizing CPU Libraries (AOCL). For Linux, COMSOL also includes the Arm Performance Libraries (ArmPL, the default) and the OpenBLAS library. For Apple silicon, COMSOL uses Arm Performance Libraries (ArmPL) by default, and COMSOL also includes the OpenBLAS library. For all platforms, COMSOL includes the standard BLAS and LAPACK libraries. It is also possible to supply another BLAS library optimized for your hardware. See BLAS Options (Windows), BLAS Options (Linux), or BLAS Options (macOS) for information about how to override the default BLAS library. If the library you want to use is unavailable or incorrectly installed, COMSOL Multiphysics switches to the default BLAS library.