Dear Petsc team, I would like to play with the ordering of a DMDA application. To be exact, I would like to change the order in which a forward SOR/Gauss Seidel preconditioner iterates over the domain. e.g. change from [x,y,z,dof] to [z, yend->ystart, xend->xstart, dof] As I see it, I could a) reorder the application, i.e. how data is stored in the DMDA b) apply a mat reordering (happy to have the reordering only happening locally) c) or implement a custom PC (or using a PCShell?) I don't like a) because it would be very laborious and intrusive and I don't even know if it is worth it. Implementing a custom PC might give the most freedom but reduces solver configurability that I like. And how bad would a SOR be if it were to jump around in memory compared to the performance and memory needs of a mat reordering? I wanted to ask if you have any other suggestions and which approach you would recommend. Many thanks, Fabian