HJfem_lite

Finite element assembly routines for linear triangles and tetrahedra. Also simple 3D visualization.

These files offer three efficient assembly techniques for the finite element method. The test cases are linear, continuous triangles and tetrahedra for the Poisson problem in the unit square or unit cube.

The first method is a straightforward assembly in which the loop over the elements is vectorized.

The second method decouples the local integration from the affine mapping (in addition to vectorizing the loop over the elements). This method is very efficient if large number of integration points is required (e.g. for high order elements).

The third method is a variant of the first method. In this method the assembly is done in few sets rather than all the elements at once to save memory.

The focus in this work is the efficiency of the assembly. In our tests, these methods can assemble 2654208 triangles (1329409 dofs) or 274625 tetrahedra (1572864 dofs) using a regular desktop computer in less than 10 seconds (wall clock time).

In addition, the there is a very simple visualization tool for the 3D results.