# MatQRFactorSymbolic
Performs symbolic QR factorization of matrix. Call this routine after `MatGetFactor()` but before calling `MatQRFactorNumeric()`. 
## Synopsis
```
#include "petscmat.h" 
PetscErrorCode MatQRFactorSymbolic(Mat fact, Mat mat, IS col, const MatFactorInfo *info)
```
Collective on fact


## Input Parameters

- ***fact -*** the factor matrix obtained with `MatGetFactor()`
- ***mat -*** the matrix
- ***col -*** column permutation
- ***info -*** options for factorization, includes


```none
          fill - expected fill as ratio of original fill.
          dtcol - pivot tolerance (0 no pivot, 1 full column pivoting)
                   Run with the option -info to determine an optimal value to use
```





## Note
Most users should employ the `KSP` interface for linear solvers
instead of working directly with matrix algebra routines such as this.
See, e.g., `KSPCreate()`.


## Developer Note
The Fortran interface is not autogenerated as the
interface definition cannot be generated correctly [due to `MatFactorInfo`]


## See Also
 `Mat`, [Matrix Factorization](sec_matfactor), `MatGetFactor()`, `MatFactorInfo`, `MatQRFactor()`, `MatQRFactorNumeric()`, `MatLUFactor()`, `MatFactorInfo`, `MatFactorInfoInitialize()`

## Level
developer

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

## Implementations

<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/aij/seq/spqr/aijspqr.c.html#MatQRFactorSymbolic_SPQR">MatQRFactorSymbolic_SPQR in src/mat/impls/aij/seq/spqr/aijspqr.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/dense/seq/dense.c.html#MatQRFactorSymbolic_SeqDense">MatQRFactorSymbolic_SeqDense in src/mat/impls/dense/seq/dense.c</A><BR>


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