Introduction¶

The GetFEM project focuses on the development of a generic and efficient C++ library for finite element methods elementary computations. The goal is to provide a library allowing the computation of any elementary matrix (even for mixed finite element methods) on the largest class of methods and elements, and for arbitrary dimension (i.e. not only 2D and 3D problems).

It offers a complete separation between integration methods (exact or approximated), geometric transformations (linear or not) and finite element methods of arbitrary degrees. It can really relieve a more integrated finite element code of technical difficulties of elementary computations.

Examples of available finite element method are : Pk on simplices in arbitrary degrees and dimensions, Qk on parallelepipeds, P1, P2 with bubble functions, Hermite elements, elements with hierarchic basis (for multigrid methods for instance), discontinuous Pk or Qk, XFem, Argyris, HCT, Raviart-Thomas, etc.

The addition of a new finite element method is straightforward. Its description on the reference element must be provided (in most of the cases, this is the description of the basis functions, and nothing more). Extensions are provided for Hermite elements, piecewise polynomial, non-polynomial and vectorial elements, XFem.

The library also includes the usual tools for finite elements such as assembly procedures for classical PDEs, interpolation methods, computation of norms, mesh operations, boundary conditions, post-processing tools such as extraction of slices from a mesh, etc.

GetFEM can be used to build very general finite elements codes, where the finite elements, integration methods, dimension of the meshes, are just some parameters that can be changed very easily, thus allowing a large spectrum of experimentations. Numerous examples are available in the tests directory of the distribution.

GetFEM has only a (very) experimental meshing procedure (and produces regular meshes), hence it is generally necessary to import meshes. Imports formats currently known by GetFEM are GiD, Gmsh and emc2 mesh files. However, given a mesh, it is possible to refine it automatically.