# tensorplay.functional.geqrf

Source: https://www.tensorplay.cn/docs/generated/tensorplay.functional.geqrf.html

```python
tensorplay.functional.geqrf(input, *, out=None)
```

This is a low-level function for calling LAPACK’s geqrf directly. This function
returns a namedtuple (a, tau) as defined in [LAPACK documentation for geqrf](http://www.netlib.org/lapack/explore-html/df/dc5/group__variants_g_ecomputational_ga3766ea903391b5cf9008132f7440ec7b.html) .

Computes a QR decomposition of input.
Both Q and R matrices are stored in the same output tensor a.
The elements of R are stored on and above the diagonal.
Elementary reflectors (or Householder vectors) implicitly defining matrix Q
are stored below the diagonal.
The results of this function can be used together with [tensorplay.linalg.householder_product()](/docs/generated/tensorplay.linalg.householder_product.html#tensorplay.linalg.householder_product)
to obtain the Q matrix or
with tensorplay.ormqr(), which uses an implicit representation of the Q matrix,
for an efficient matrix-matrix multiplication.

See [LAPACK documentation for geqrf](http://www.netlib.org/lapack/explore-html/df/dc5/group__variants_g_ecomputational_ga3766ea903391b5cf9008132f7440ec7b.html) for further details.

> **Note**
>
> See also tensorplay.linalg.qr(), which computes Q and R matrices, and tensorplay.linalg.lstsq() with the driver="gels" option for a function that can solve matrix equations using a QR decomposition.

Parameters:

input ([Tensor](/docs/generated/tensorplay.Tensor.html#tensorplay.Tensor)) – the input matrix

Keyword Arguments:

out ([tuple](https://docs.python.org/3/builtins/stdtypes.html#tuple), optional) – the output tuple of (Tensor, Tensor). Ignored if None. Default: None.