petsc-3.12.5 2020-03-29

PCMGSetRestriction

Sets the function to be used to restrict dual vectors from level l to l-1.

#include "petscksp.h" 
PetscErrorCode  PCMGSetRestriction(PC pc,PetscInt l,Mat mat)

Logically Collective on PC

	pc	- the multigrid context
	l	- the level (0 is coarsest) to supply [Do not supply 0]
	mat	- the restriction matrix

Usually this is the same matrix used also to set the interpolation for the same level.

One can pass in the interpolation matrix or its transpose; PETSc figures out from the matrix size which one it is.

If you do not set this, the transpose of the Mat set with PCMGSetInterpolation() is used.

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