# MatSetValuesBlockedStencil
Inserts or adds a block of values into a matrix. Using structured grid indexing 
## Synopsis
```
#include "petscmat.h" 
PetscErrorCode MatSetValuesBlockedStencil(Mat mat, PetscInt m, const MatStencil idxm[], PetscInt n, const MatStencil idxn[], const PetscScalar v[], InsertMode addv)
```
Not Collective


## Input Parameters

- ***mat -*** the matrix
- ***m -*** number of rows being entered
- ***idxm -*** grid coordinates for matrix rows being entered
- ***n -*** number of columns being entered
- ***idxn -*** grid coordinates for matrix columns being entered
- ***v -*** a logically two-dimensional array of values
- ***addv -*** either `ADD_VALUES` to add to existing entries or `INSERT_VALUES` to replace existing entries with new values





## Notes
By default the values, v, are row-oriented and unsorted.
See `MatSetOption()` for other options.

Calls to `MatSetValuesBlockedStencil()` with the `INSERT_VALUES` and `ADD_VALUES`
options cannot be mixed without intervening calls to the assembly
routines.

The grid coordinates are across the entire grid, not just the local portion

`MatSetValuesBlockedStencil()` uses 0-based row and column numbers in Fortran
as well as in C.

For setting/accessing vector values via array coordinates you can use the `DMDAVecGetArray()` routine

In order to use this routine you must either obtain the matrix with `DMCreateMatrix()`
or call `MatSetBlockSize()`, `MatSetLocalToGlobalMapping()` and `MatSetStencil()` first.

The columns and rows in the stencil passed in MUST be contained within the
ghost region of the given process as set with DMDACreateXXX() or `MatSetStencil()`. For example,
if you create a `DMDA` with an overlap of one grid level and on a particular process its first
local nonghost x logical coordinate is 6 (so its first ghost x logical coordinate is 5) the
first i index you can use in your column and row indices in `MatSetStencil()` is 5.

Negative indices may be passed in idxm and idxn, these rows and columns are
simply ignored. This allows easily inserting element stiffness matrices
with homogeneous Dirchlet boundary conditions that you don't want represented
in the matrix.

Inspired by the structured grid interface to the HYPRE package
(https://computation.llnl.gov/projects/hypre-scalable-linear-solvers-multigrid-methods)


## Fortran Note
In Fortran idxm and idxn should be declared as
```none
MatStencil idxm(4,m),idxn(4,n)
```
and the values inserted using
```none
    idxm(MatStencil_i,1) = i
    idxm(MatStencil_j,1) = j
    idxm(MatStencil_k,1) = k
   etc
```



## See Also
 `Mat`, `DMDA`, `MatSetOption()`, `MatAssemblyBegin()`, `MatAssemblyEnd()`, `MatSetValuesBlocked()`, `MatSetValuesLocal()`
`MatSetValues()`, `MatSetValuesStencil()`, `MatSetStencil()`, `DMCreateMatrix()`, `DMDAVecGetArray()`, `MatStencil`,
`MatSetBlockSize()`, `MatSetLocalToGlobalMapping()`

## Level
beginner

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/interface/matrix.c.html#MatSetValuesBlockedStencil">src/mat/interface/matrix.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex48.c.html">src/snes/tutorials/ex48.c.html</A><BR>


---
[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/mat/interface/matrix.c)


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