PCBJACOBI#
Use block Jacobi preconditioning, each block is (approximately) solved with its own KSP object.
Options Database Keys#
-pc_use_amat - use Amat to apply block of operator in inner Krylov method
-pc_bjacobi_blocks
- use n total blocks
Notes#
See PCJACOBI for diagonal Jacobi, PCVPBJACOBI for variable point block, and PCPBJACOBI for fixed size point block
Each processor can have one or more blocks, or a single block can be shared by several processes. Defaults to one block per processor.
To set options on the solvers for each block append -sub_ to all the KSP and PC
options database keys. For example, -sub_pc_type ilu -sub_pc_factor_levels 1 -sub_ksp_type preonly
To set the options on the solvers separate for each block call PCBJacobiGetSubKSP()
and set the options directly on the resulting KSP object (you can access its PC
KSPGetPC())
For GPU-based vectors (VECCUDA, VECViennaCL) it is recommended to use exactly one block per MPI process for best
performance. Different block partitioning may lead to additional data transfers
between host and GPU that lead to degraded performance.
When multiple processes share a single block, each block encompasses exactly all the unknowns owned its set of processes.
See Also#
KSP: Linear System Solvers, PCCreate(), PCSetType(), PCType, PC, PCType,
PCASM, PCSetUseAmat(), PCGetUseAmat(), PCBJacobiGetSubKSP(), PCBJacobiSetTotalBlocks(),
PCBJacobiSetLocalBlocks(), PCSetModifySubMatrices(), PCJACOBI, PCVPBJACOBI, PCPBJACOBI
Level#
beginner
Location#
Examples#
src/ksp/ksp/tutorials/ex7.c
src/ksp/ksp/tutorials/ex86.c
src/ksp/ksp/tutorials/ex79.c
Index of all PC routines
Table of Contents for all manual pages
Index of all manual pages