Over the years this project has grown slightly bigger than it was originally expected. In its original form BETL was just intended to serve as set of methods with rather limited functionality for maintaining an existing industrial Boundary Element solver. Since then BETL has become a fully autonomous tool on which powerful Boundary Element applications can be build. BETL's strength lies in its use of well-known design principles in conjunction with state of the art C++ language features. This ensures the fast development of robust, extendable, and reliable numerical schemes and implementations which are somehow related to the discretisation of boundary integral operators.

- Support of different element types
- 3-noded triangular elements
- 6-noded triangular elements
- 10-noded triangular elements
- 4-noded quadrilateral elements
- 8-noded quadrilateral elements
- 16-noded quadrilateral elements
- Lagrangian basis functions of constant, linear, quadratic, and cubic order for triangular as well as as for quadrilateral elements
- Raviart-Thomas- and Nedelec-type basis functions up to quadratic degree for flat and curved triangular elements
- Laplace- and Helmholtz-type fundamental solutions
- A set of traces to compute
- single-layer potentials
- double-layer potentials
- hypersingular integral operators
- A set of integrators
- 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
- An interface for using the Directional Fast Multipole Method as it has been developed by M. Messner, E. Darve, and M. Schanz (published as Fast directional multilevel summation for oscillatory kernels based on Chebyshev interpolation).
- Natural semantics for linear algebra computations by using expression templates

- There is no concept of boundary conditions implemented
- The software implements no Boundary Element Methods. However, BETL comes with a bunch of tutorials which explain how to embed BETL structures into some particular Boundary Element Methods in order to solve a certain boundary value problem

- 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)