gko::multigrid

Building blocks for the algebraic-multigrid hierarchy that gko::solver::Multigrid drives. A MultigridLevel represents the fine operator together with the (restriction, coarse-operator, prolongation) triple at one level of the hierarchy, and the concrete classes here are the level generators: they take a fine-level system matrix and produce the next coarser level.

For the high-level multigrid picture, see the Multigrid solver concept page; this section covers the per-level interfaces.

The level interface

• MultigridLevel: abstract interface for one level of the hierarchy that exposes the fine operator alongside the restriction, coarse operator, and prolongation as LinOps.

Level generators

• Pgm: Parallel Graph Matching aggregation, the standard algebraic-coarsening choice in Ginkgo. Aggregates fine-level rows based on matrix values (strongest-neighbour pairing).

• FixedCoarsening: pick coarse-level rows by user-supplied index list, restricting by selection and prolonging by injection. Useful when the application already knows a good coarsening (e.g. from a structured mesh).