# MatInvertVariableBlockEnvelope
set matrix C to be the inverted block diagonal of matrix A 
## Synopsis
```
#include "petscmat.h" 
PetscErrorCode MatInvertVariableBlockEnvelope(Mat A, MatReuse reuse, Mat *C)
```
Collective on A


## Input Parameters

- ***A -*** the matrix



## Output Parameters

- ***C -*** matrix with inverted block diagonal of A.  This matrix should be created and may have its type set.



## Note
For efficiency the matrix A should have all the nonzero entries clustered in smallish blocks along the diagonal.




## See Also
 `MatInvertBlockDiagonal()`, `MatComputeBlockDiagonal()`

## Level
advanced

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


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


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