PCDeflationSetSpace#

Set the deflation space matrix (or its (Hermitian) transpose).

Synopsis#

#include "petscksp.h" 
PetscErrorCode PCDeflationSetSpace(PC pc, Mat W, PetscBool transpose)

Logically Collective

Input Parameters#

pc - the preconditioner context
W - deflation matrix
transpose - indicates that W is an explicit transpose of the deflation matrix

Notes#

Setting W as a multipliplicative MATCOMPOSITE enables use of the multilevel deflation. If W = W0W1W2*…*Wn, W0 is taken as the first deflation space and the coarse problem (W0’AW0)^{-1} is again preconditioned by deflation with W1 as the deflation matrix. This repeats until the maximum level set by PCDeflationSetLevels() is reached or there are no more matrices available. If there are matrices left after reaching the maximum level, they are merged into a deflation matrix …*W{n-1}*Wn.