MatGalerkin#

Constructs the coarse grid problem matrix via Galerkin projection.

Synopsis#

#include "petscmat.h" 
PetscErrorCode MatGalerkin(Mat restrct, Mat dA, Mat interpolate, MatReuse reuse, PetscReal fill, Mat *A)

If the interpolation and restriction operators are the same, uses MatPtAP(). If they are not the same, uses MatMatMatMult().

Once the coarse grid problem is constructed, correct for interpolation operators that are not of full rank, which can legitimately happen in the case of non-nested geometric multigrid.

Input Parameters#

restrct - restriction operator
dA - fine grid matrix
interpolate - interpolation operator
reuse - either MAT_INITIAL_MATRIX or MAT_REUSE_MATRIX
fill - expected fill, use PETSC_DETERMINE or PETSC_DETERMINE if you do not have a good estimate

Output Parameter#

A - the Galerkin coarse matrix

Options Database Key#

-pc_mg_galerkin <both,pmat,mat,none> - for what matrices the Galerkin process should be used

Note#

The deprecated PETSC_DEFAULT in fill also means use the current value

Level#

developer

Location#

src/mat/interface/matrix.c

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