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# MatIsStructurallySymmetric
Test whether a matrix is structurally symmetric
## Synopsis
```
#include "petscmat.h"
PetscErrorCode MatIsStructurallySymmetric(Mat A, PetscBool *flg)
```
Collective
## Input Parameter
- ***A -*** the matrix to test
## Output Parameter
- ***flg -*** the result
## Notes
If the matrix does yet know it is structurally symmetric this can be an expensive operation, also available `MatIsStructurallySymmetricKnown()`
One can declare that a matrix is structurally symmetric with `MatSetOption`(mat,`MAT_STRUCTURALLY_SYMMETRIC`,`PETSC_TRUE`) and if it is known to remain structurally
symmetric after changes to the matrices values one can call `MatSetOption`(mat,`MAT_STRUCTURAL_SYMMETRY_ETERNAL`,`PETSC_TRUE`)
## See Also
[](ch_matrices), `Mat`, `MAT_STRUCTURALLY_SYMMETRIC`, `MAT_STRUCTURAL_SYMMETRY_ETERNAL`, `MatTranspose()`, `MatIsTranspose()`, `MatIsHermitian()`, `MatIsSymmetric()`, `MatSetOption()`, `MatIsStructurallySymmetricKnown()`
## Level
intermediate
## Location
src/mat/interface/matrix.c
## Implementations
MatIsStructurallySymmetric_IS in src/mat/impls/is/matis.c
MatIsStructurallySymmetric_SeqSBAIJ in src/mat/impls/sbaij/seq/sbaij.c
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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/mat/interface/matrix.c)
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