PCSPAISetBlockSize#
set the block size for the PCSPAI preconditioner
Synopsis#
#include "petscpc.h"
PetscErrorCode PCSPAISetBlockSize(PC pc, PetscInt block_size1)
Input Parameters#
pc - the preconditioner
block_size1 - block size (default 1)
Notes#
A block size of 1 treats A as a matrix of scalar elements. A block size of s > 1 treats A as a matrix of sxs blocks. A block size of 0 treats A as a matrix with variable sized blocks, which are determined by searching for dense square diagonal blocks in A. This can be very effective for finite-element matrices.
SPAI will convert A to block form, use a block version of the preconditioner algorithm, and then convert the result back to scalar form.
In many cases the a block-size parameter other than 1 can lead to very significant improvement in performance.
Developer Note#
This preconditioner could use the matrix block size as the default block size to use
See Also#
Level#
intermediate
Location#
Implementations#
PCSPAISetBlockSize_SPAI() in src/ksp/pc/impls/spai/ispai.c
Index of all PC routines
Table of Contents for all manual pages
Index of all manual pages