# MatQRFactor
Performs in-place QR factorization of matrix. 
## Synopsis
```
#include "petscmat.h" 
PetscErrorCode MatQRFactor(Mat mat, IS col, const MatFactorInfo *info)
```
Collective


## Input Parameters

- ***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
```





## Notes
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()`.

This changes the state of the matrix to a factored matrix; it cannot be used
for example with `MatSetValues()` unless one first calls `MatSetUnfactored()`.


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


## See Also
 [Matrix Factorization](sec_matfactor), `MatFactorInfo`, `MatGetFactor()`, `MatQRFactorSymbolic()`, `MatQRFactorNumeric()`, `MatLUFactor()`,
`MatSetUnfactored()`, `MatFactorInfo`, `MatGetFactor()`

## Level
developer

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

## Implementations

<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/dense/seq/cuda/densecuda.cu.html#MatQRFactor_SeqDenseCUDA">MatQRFactor_SeqDenseCUDA in src/mat/impls/dense/seq/cuda/densecuda.cu</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/dense/seq/dense.c.html#MatQRFactor_SeqDense">MatQRFactor_SeqDense in src/mat/impls/dense/seq/dense.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/dense/seq/hip/densehip.hip.c.html#MatQRFactor_SeqDenseHIP">MatQRFactor_SeqDenseHIP in src/mat/impls/dense/seq/hip/densehip.hip.c</A><BR>


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


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