FEM solver for 2D Helmholtz equation

P1 fully vectorized FEM solver for the homogeneous 2D Helmholtz equation on arbitrary geometries.

This solver assembles and solves the FEM for the 2D scalar Helmholtz equation, using P1 triangular elements. The assembly is fully vectorized for efficiency.
For tutoring, the script of a "pedagogic" naive assembly is also provided in comments.
The resolution is performed using the Matlab \ operator (here leads to LU factorization).
Five different geometries are provided using built-in Matlab tools, but the solver is also compatible with arbitrary geometries. In particular, external mesh files (for instance from GMSH) can be used, while satisfying the PET format.