Reducing computational costs using a multi-region finite element method for electromagnetic scattering

Electromagnetic scattering problems involving multiple scatterers can be solved by the finite element method using a single domain truncated with an absorbing boundary condition, but often it is more efficient to separate the single domain into several subdomains, separated by free-space, and to solve the set of subdomains iteratively. This multi-region method has been reported in the literature. Its relative computational cost is investigated and formulas for determining are provided when it is advantageous to use a multi-region against a single-region method.