petsc-3.14.6 2021-03-30

SNESFASSetRestriction

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

#include "petscsnes.h"  
PetscErrorCode SNESFASSetRestriction(SNES snes, PetscInt level, Mat mat)

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

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 SNESFASSetInterpolation() is used.

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