This section describes Sparse BLAS Level 2 and Level 3 routines included in the

Intel® oneAPI Math Kernel Library (oneMKL)

. Sparse BLAS Level 2 is a group of routines and functions that perform operations between a sparse matrix and dense vectors. Sparse BLAS Level 3 is a group of routines and functions that perform operations between a sparse matrix and dense matrices.

The terms and concepts required to understand the use of the

Intel® oneAPI Math Kernel Library

Sparse BLAS Level 2 and Level 3 routines are discussed in theLinear Solvers Basics appendix.

The Sparse BLAS routines can be useful to implement iterative methods for solving large sparse systems of equations or eigenvalue problems. For example, these routines can be considered as building blocks for Iterative Sparse Solvers based on Reverse Communication Interface (RCI ISS).

Intel® oneAPI Math Kernel Library

provides Sparse BLAS Level 2 and Level 3 routines with typical (or conventional) interface similar to the interface used in the NIST* Sparse BLAS library [Rem05].

Some software packages and libraries (the PARDISO* Solverused in

Intel® oneAPI Math Kernel Library

,

Sparskit 2

[Saad94], the Compaq* Extended Math Library (CXML)[CXML01]) use different (early) variation of the compressed sparse row (CSR) format and support only Level 2 operations with simplified interfaces.

Intel® oneAPI Math Kernel Library

provides an additional set of Sparse BLAS Level 2 routines with similar simplified interfaces. Each of these routines operates only on a matrix of the fixed type.

The routines described in this section support both one-based indexing and zero-based indexing of the input data (see details in the section One-based and Zero-based Indexing).