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# MatIsSymmetricKnown
Checks if a matrix knows if it is symmetric or not and its symmetric state 
## Synopsis
```
#include "petscmat.h" 
PetscErrorCode MatIsSymmetricKnown(Mat A, PetscBool *set, PetscBool *flg)
```
Not Collective


## Input Parameter

- ***A -*** the matrix to check



## Output Parameters

- ***set -*** `PETSC_TRUE` if the matrix knows its symmetry state (this tells you if the next flag is valid)
- ***flg -*** the result (only valid if set is `PETSC_TRUE`)





## Notes
Does not check the matrix values directly, so this may return unknown (set = `PETSC_FALSE`). Use `MatIsSymmetric()`
if you want it explicitly checked

One can declare that a matrix is symmetric with `MatSetOption`(mat,`MAT_SYMMETRIC`,`PETSC_TRUE`) and if it is known to remain symmetric
after changes to the matrices values one can call `MatSetOption`(mat,`MAT_SYMMETRY_ETERNAL`,`PETSC_TRUE`)


## See Also
 [](ch_matrices), `Mat`, `MAT_SYMMETRY_ETERNAL`, `MatTranspose()`, `MatIsTranspose()`, `MatIsHermitian()`, `MatIsStructurallySymmetric()`, `MatSetOption()`, `MatIsSymmetric()`, `MatIsHermitianKnown()`

## Level
advanced

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