PETSc version 3.16.6
MatGetValuesLocal
retrieves values from certain locations in a matrix using the local numbering of the indices defined previously by MatSetLocalToGlobalMapping()
Synopsis
#include "petscmat.h"
PetscErrorCode MatGetValuesLocal(Mat mat,PetscInt nrow,const PetscInt irow[],PetscInt ncol,const PetscInt icol[],PetscScalar y[])
Not Collective
Input Parameters
| mat | - the matrix
|
| nrow, irow | - number of rows and their local indices
|
| ncol, icol | - number of columns and their local indices
|
Output Parameter
| y | - a logically two-dimensional array of values
|
Notes
If you create the matrix yourself (that is not with a call to DMCreateMatrix()) then you MUST call MatSetLocalToGlobalMapping() before using this routine.
This routine can only return values that are owned by the requesting MPI rank. That is, for standard matrix formats, rows that, in the global numbering,
are greater than or equal to rstart and less than rend where rstart and rend are obtainable from MatGetOwnershipRange(mat,&rstart,&rend). One can
determine if the resulting global row associated with the local row r is owned by the requesting MPI rank by applying the ISLocalToGlobalMapping set
with MatSetLocalToGlobalMapping().
Developer Notes
This is labelled with C so does not automatically generate Fortran stubs and interfaces
because it requires multiple Fortran interfaces depending on which arguments are scalar or arrays.
See Also
MatAssemblyBegin(), MatAssemblyEnd(), MatSetValues(), MatSetLocalToGlobalMapping(),
MatSetValuesLocal(), MatGetValues()
Level
advanced
Location
src/mat/interface/matrix.c
Index of all Mat routines
Table of Contents for all manual pages
Index of all manual pages