The Domain Manager acts as a repository for the current state and the history of the finite elements mesh and its associated decompositions. Moreover, it provides a unified mesh refinement/domain decomposition service. Finally, it provides the initial mesh at cold boot or on restart. For saving memory space, as the computation is not supposed to be out of core, the Domain Manager only sees a simplified version of the mesh data (basic domain structure in the following).
On a mesh refinement request, the Domain Manager always performs the required refinement, and can also decide to split the requesting domain in two subdomains or to merge two subdomains. The decision to split or merge depends on two factors: memory space, and load balancing. Memory space limitation is easy to compute, because the actual memory size needed by the vectors and sparse matrices defined on a domain can be accurately predicted from the basic domain structure. Load balancing is much trickier, because the convergence time for the non-linear iterations has to be predicted.