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# PCBJKOKKOS

A batched Krylov/block Jacobi solver that runs a solve of each diagaonl block of a block diagonal `MATSEQAIJ` in a Kokkos thread group

## Options Database Key

- -pc_bjkokkos_ - options prefix for its `KSP` options

## Note

For use with `-ksp_type preonly` to bypass any computation on the CPU

## Developer Notes

The entire Krylov (TFQMR or BICG) with diagonal preconditioning for each block of a block diagnaol matrix runs in a Kokkos thread group (eg, one block per SM on NVIDIA). It supports taking a non-block diagonal matrix but this is not tested. One should create an explicit block diagonal matrix and use that as the matrix for constructing the preconditioner in the outer `KSP` solver. Variable block size are supported and tested in src/ts/utils/dmplexlandau/tutorials/ex[1|2].c

## See Also

KSP: Linear System Solvers, `PCCreate()`, `PCSetType()`, `PCType`, `PC`, `PCBJACOBI`, `PCSHELL`, `PCCOMPOSITE`, `PCSetUseAmat()`, `PCBJKOKKOSGetKSP()`

## Level

intermediate

## Location

src/ksp/pc/impls/bjacobi/bjkokkos/bjkokkos.kokkos.cxx

Index of all PC routines
Table of Contents for all manual pages
Index of all manual pages