MatShellGetScalingShifts#

Gets members of a MATSHELL used internally for scaling and shifting the Mat or calling MatAXPY(), MatZeroRows(), or MatZeroRowsColumns() with it

Synopsis#

#include "petscmat.h" 
PetscErrorCode MatShellGetScalingShifts(Mat A, PetscScalar *vshift, PetscScalar *vscale, Vec *dshift, Vec *left, Vec *right, Mat *axpy, IS *zrows, IS *zcols)

Logically Collective

Input Parameter#

A - the MATSHELL shell matrix

Output Parameters#

vshift - PetscScalar pointer (can be NULL), see MatShift(), or MAT_SHELL_NOT_ALLOWED if the internal shift should be 0
vscale - PetscScalar pointer (can be NULL), see MatScale(), or MAT_SHELL_NOT_ALLOWED if the internal scaling should be 1
dshift - Vec pointer (can be NULL), see MatDiagonalSet(), or MAT_SHELL_NOT_ALLOWED if the internal shift should be NULL
left - Vec pointer (can be NULL), see MatDiagonalScale(), or MAT_SHELL_NOT_ALLOWED if the internal scaling should be NULL
right - Vec pointer (can be NULL), see MatDiagonalScale(), or MAT_SHELL_NOT_ALLOWED if the internal scaling should be NULL
axpy - Mat pointer (can be NULL), or MAT_SHELL_NOT_ALLOWED if MatAXPY() should have not been called on A
zrows - Vec pointer (can be NULL), or MAT_SHELL_NOT_ALLOWED if MatZeroRows() should have not been called on A
zcols - Vec pointer (can be NULL), or MAT_SHELL_NOT_ALLOWED if MatZeroRowsColumns() should have not been called on A

Developer Notes#

This is mostly useful to check for corner-cases in MatType deriving from MATSHELL, e.g, MATCOMPOSITE or MATTRANSPOSEVIRTUAL, since scaling and shifts often require extra work which is not always implemented.

Level#

advanced

Location#

src/mat/impls/shell/shell.c

Implementations#

MatShellGetScalingShifts_Shell() in src/mat/impls/shell/shell.c

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