block-diag-ilu 0.2.2

block_diag_ilu is a C++ implementation of an incomplete LU factorization.

block_diag_ilu is an open source C++ single header-file implementeation of an incomplete LU decomposition routine suitable for diagonally dominant (square) block diagonal matrices with sub- and super diagonals of small magnitude. It is useful for preconditioning linear systems. The usecase in mind is for integrating discretized PDEs of mixed chemical kinetics / diffusion problems where the diffusion process may be accurately considered a mild perturbation.

A picture is woth a thousant words, so if your matrix looks anything like this:

its LU decomposition then looks like this:

then block_diag_ilu should be able to save quite a bit of time when solving linear systems approximately, e.g. for preconditioning.

Conditional compilation

The following macros affect the compilation:

Macro name	Action (when defined)	Default
NDEBUG	use std::unique_ptr instead of std::vector as underlying data structure.	undefined
WITH_BLOCK_DIAG_ILU_DGETRF	Use unblocked (parallell) internal implementation of LAPACK’s dgetrf (uses OpenMP)	undefined

License

The source code is Open Source and is released under the very permissive “simplified (2-clause) BSD license”. See LICENSE.txt for further details.

Contributors are welcome to suggest improvements at https://github.com/chemreac/block_diag_ilu

Author

Björn Dahlgren, contact:

• gmail adress: bjodah

• kth.se adress: bda