Redistributes a matrix for load balancing, removing the rows (and the corresponding columns) that only have a diagonal entry and then applies a
KSP to that new smaller matrix
Usually run this with
If you have used
MatZeroRows() to eliminate (for example, Dirichlet) boundary conditions for a symmetric problem then you can use, for example,
-ksp_type preonly -pc_type redistribute -redistribute_ksp_type cg -redistribute_pc_type bjacobi -redistribute_sub_pc_type icc to take advantage of the symmetry.
Supports the function
PCFieldSplitSetIS(); passs the appropriate reduced field indices to an inner
PCFIELDSPLIT, set with, for example
-ksp_type preonly -pc_type redistribute -redistribute_pc_type fieldsplit. Does not support the PCFIELDSPLIT` options database keys.
This does NOT call a partitioner to reorder rows to lower communication; the ordering of the rows in the original matrix and redistributed matrix is the same. Rows are moved between MPI processes inside the preconditioner to balance the number of rows on each process.
Should add an option to this preconditioner to use a partitioner to redistribute the rows to lower communication.