# "Optimal" domain partitioning in domain decomposition algorithms

When solving a PDE numerically by domain decomposition methods, what is the "optimal way" to split the domain? Are there any results stating that a particular partition of the domain yields "better" convergence than other partitions?

For concreteness, let us consider the classical Poisson equation $$-\Delta u = f(x)$$ with homogeneous Dirichlet boundary conditions.