# MatCreateKAIJ#

Creates a matrix of type `MATKAIJ`

to be used for matrices of the following form:

## Synopsis#

```
#include "petscmat.h"
PetscErrorCode MatCreateKAIJ(Mat A, PetscInt p, PetscInt q, const PetscScalar S[], const PetscScalar T[], Mat *kaij)
```

[I \otimes S + A \otimes T]

where
S is a dense (p \times q) matrix
T is a dense (p \times q) matrix
A is an `MATAIJ`

(n \times n) matrix
I is the identity matrix
The resulting matrix is (np \times nq)

S and T are always stored independently on all processes as `PetscScalar`

arrays in column-major format.

Collective

## Input Parameters#

the**A -**`MATAIJ`

matrixnumber of rows in S and T**p -**number of columns in S and T**q -**the S matrix (can be NULL), stored as a**S -**`PetscScalar`

array (column-major)the T matrix (can be NULL), stored as a**T -**`PetscScalar`

array (column-major)

## Output Parameter#

the new**kaij -**`MATKAIJ`

matrix

## Notes#

This function increases the reference count on the `MATAIJ`

matrix, so the user is free to destroy the matrix if it is not needed.

Changes to the entries of the `MATAIJ`

matrix will immediately affect the `MATKAIJ`

matrix.

## Developer Note#

In the `MATMPIKAIJ`

case, the internal ‘AIJ’ and ‘OAIJ’ sequential KAIJ matrices are kept up to date by tracking the object state
of the AIJ matrix ‘A’ that describes the blockwise action of the MATMPIKAIJ matrix and, if the object state has changed, lazily
rebuilding ‘AIJ’ and ‘OAIJ’ just before executing operations with the MATMPIKAIJ matrix. If new types of operations are added,
routines implementing those must also ensure these are rebuilt when needed (by calling the internal MatKAIJ_build_AIJ_OAIJ() routine).

## See Also#

`MatKAIJSetAIJ()`

, `MatKAIJSetS()`

, `MatKAIJSetT()`

, `MatKAIJGetAIJ()`

, `MatKAIJGetS()`

, `MatKAIJGetT()`

, `MATKAIJ`

## Level#

advanced

## Location#

## Examples#

src/ksp/ksp/tutorials/ex74.c.html

src/ksp/ksp/tutorials/ex77.c.html

Index of all Mat routines

Table of Contents for all manual pages

Index of all manual pages