petsc-3.9.4 2018-09-11

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.

FAS, MG, set, multigrid, restriction, level

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