The octree-mg library implements parallel geometric multigrid methods on quadtree/octree grids, which can be used to solve elliptic PDEs such as Poissons's equation. The provided solvers can be used in existing adaptive-mesh-refinement (AMR) frameworks that employ quadtree/octree grids.
The code is described in detail in the publication A geometric multigrid library for quadtree/octree AMR grids coupled to MPI-AMRVAC, also available at arXiv.
Type make in the top folder, and run the programs in the tests folder.
You can either include a full copy of octree-mg using e.g. git submodules of subtrees, or include it as a single Fortran module, see the folder single_module.
- MPI parallelization
- The same code can be used in 2D/3D (compiled into two different libraries)
- Support for adaptively refined grids, with a consistent discretization near refinement boundaries
- Rectangular grids can easily be created (e.g. 512 x 256 x 256 cells).
- Operators with sparse stencils (5/7-point in 2D/3D) are supported
- Support for periodic, Dirichlet, Neumann, and continuous boundary conditions
- Coarse grids are automatically created
- One layer of ghost cells is used, and diagonal ghost cells are currently not set. This means stencils with diagonal elements are not possible.
- Point-wise smoothers are employed, so currently a requirement is that dx, dy and dz are similar
The "single-module" version of this library is included in MPI-AMRVAC, but it does not include the free-space module. An example of how to do this can be found under tests/multigrid/free_space_3d in the MPI-AMRVAC folder, see in particular the file local.make.