MatPtAP#

Creates the matrix product \(C = P^T * A * P\)

Synopsis#

#include "petscmat.h" 
PetscErrorCode MatPtAP(Mat A, Mat P, MatReuse scall, PetscReal fill, Mat *C)

Neighbor-wise Collective

A - the matrix
P - the projection matrix
scall - either MAT_INITIAL_MATRIX or MAT_REUSE_MATRIX
fill - expected fill as ratio of nnz(C)/(nnz(A) + nnz(P)), use PETSC_DETERMINE or PETSC_CURRENT if you do not have a good estimate if the result is a dense matrix this is irrelevant

C will be created and must be destroyed by the user with MatDestroy().

This is a convenience routine that wraps the use of the MatProductCreate() with a MatProductType of MATPRODUCT_PtAP functionality into a single function call. For more involved matrix-matrix operations see MatProductCreate().

The deprecated PETSC_DEFAULT in fill also means use the current value

For matrix types without special implementation the function fallbacks to MatMatMult() followed by MatTransposeMatMult().

intermediate