What is METIS?
When running parallel in “domains”, octopus divides the simulation region (the box) into separate regions (domains) and assigns each of these to a different processor. This lets you not only speed up the calculation, but also divide the memory among the different processors. The first step of this process, the splitting of the box, is in general a very complicated process. Note that we are talking about a simulation box of an almost arbitrary shape, and of an arbitrary number of processors. Furthermore, as the communication between processors grows proportionally to the surface of the domains, one should use an algorithm that divides the box such that each domain has the same number of points, and at the same time minimizes the total area of the domains. The METIS library does just that. If you want to run octopus parallel in domains you are required use it (or the similar Zoltan library). Currently METIS and Zoltan are included in the Octopus distribution and are compiled by default w
