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

Input Parameters

• 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

Output Parameter

• C - the product matrix

Notes

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

An alternative approach to this function is to use MatProductCreate() and set the desired options before the computation is done

The deprecated PETSC_DEFAULT in fill also means use the current value

Developer Note

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

See Also

Matrices, Mat, MatProductCreate(), MatMatMult(), MatRARt()

Level

intermediate

Location

src/mat/interface/matrix.c

Examples

src/ksp/ksp/tutorials/ex76.c
src/tao/pde_constrained/tutorials/elliptic.c

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