About BETL

BETL2 is a C++ template library providing a framework for the implementation of low-order piecewise polynomial boundary element and finite element Galerkin discretization of boundary value problems as they arise in various physical and engineering applications. Prominent examples are, e.g., electrostatic or thermal models as well as the scattering of acoustic and electromagnetic waves.
BETL2 implements a slightly modified and extended DUNE style interface for handling meshes. It heavily uses template programming to achieve flexibility with minimal runtime overhead.
This ensures the fast development of robust, extendable, and reliable numerical schemes and implementations which for the discretization of boundary value problems. operators.
While BETL2 currently implements the discretisation of 3-dimensional boundary integral operators via Galerkin schemes its design principles allow also for the incorporation of other discretisation schemes such as, e.g., the still popular collocation methods.

Main features of BETL

BETL mainly aims on the discretisation of quite general boundary integral operators and volume variational formulations. The following list gives a rough overview on BETL's main features.

• Support of hybrid 2D and 3D meshes somprising various element types
• Lagrangian basis functions of constant, linear, quadratic, and cubic order for many element types
• Raviart-Thomas- and Nedelec-type basis functions up to quadratic degree
• Laplace- and Helmholtz-type fundamental solutions
• Galerkin discretization of various integral operators for scalar 2nd-order elliptic boundary value problems and Maxwell's equations in frequency domain.
• Computation of entries of Galerkin matrices for boundary integral operators:
  • General integrators are based on formulas developed by S. Sauter and C. Schwab. They cover quite arbitrary weak- and strongly-singular integral kernels
  • Semi-analytic integrators for the Laplace kernel on 3-noded triangular elements are based on routines which have been developed by O. Steinbach and his group
    
• Lean interfaces for sparse direct solvers such as UMFPACK, SuperLU, and Pardiso
• A simple-to-use interface for the incorporation of the AHMED library developed by M. Bebendorf

Documentation

If you are interested, please have a look at the documentation for further details about BETL. Currently, BETL's documentation is still under construction. Nevertheless, the documentation is already freely available and may be found under the following links.

• HTML-version
• pdf-version

The source code's Doxygen documentation will be also available.

Publications

• A BETL related talk: Söllerhaus Workshop, September 2012
• R. Hiptmair, L. Kielhorn: BETL — A generic boundary element template library, Tech. Rep. 2012-36, Seminar for Applied Mathematics, ETH Zürich (pdf, sources, meshes (33MB), aca settings)
  
• L. Kielhorn: Matrix-vector computations with BETL, Tech. Note, Seminar for Applied Mathematics, ETH Zürich (pdf)
• A BETL poster: Swiss Numerics Colloquium 2013 (pdf)

Obtaining BET2L

BETL has originated from an industrial environment and is also used for commercial projects. This is the main reason why the license agreement prohibits any commercial use of this software. Despite this, BETL2 is free for academic use in research and teaching. Interested users are granted access to the subversion repository after their academic affiliation has been proven. For this, simply complete the license agreement and send it together with an attached copy of your academic affiliation via e-mail either to Lars Kielhorn or to Ralf Hiptmair.