---
name: "dlarfx.f"
section: "3"
platform: "linux"
package: "lapack-doc"
version: "3.12.1-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/dlarfx.f"
---

# dlarfx.f(3)

## NAME

SRC/dlarfx.f

## SYNOPSIS

### Functions/Subroutines

subroutine **dlarfx** (side, m, n, v, tau, c, ldc, work)\
 **DLARFX** applies an elementary reflector to a general rectangular matrix, with loop unrolling when the reflector has order ≤ 10.

## Function/Subroutine Documentation

### subroutine dlarfx (character side, integer m, integer n, double precision, dimension( \* ) v, double precision tau, double precision, dimension( ldc, \* ) c, integer ldc, double precision, dimension( \* ) work)

**DLARFX** applies an elementary reflector to a general rectangular matrix, with loop unrolling when the reflector has order ≤ 10.

**Purpose:**

```
!>
!> DLARFX applies a real elementary reflector H to a real m by n
!> matrix C, from either the left or the right. H is represented in the
!> form
!>
!>       H = I - tau * v * v**T
!>
!> where tau is a real scalar and v is a real vector.
!>
!> If tau = 0, then H is taken to be the unit matrix
!>
!> This version uses inline code if H has order < 11.
!>
```

**Parameters**

*SIDE*

```
!>          SIDE is CHARACTER*1
!>          = 'L': form  H * C
!>          = 'R': form  C * H
!>
```

*M*

```
!>          M is INTEGER
!>          The number of rows of the matrix C.
!>
```

*N*

```
!>          N is INTEGER
!>          The number of columns of the matrix C.
!>
```

*V*

```
!>          V is DOUBLE PRECISION array, dimension (M) if SIDE = 'L'
!>                                     or (N) if SIDE = 'R'
!>          The vector v in the representation of H.
!>
```

*TAU*

```
!>          TAU is DOUBLE PRECISION
!>          The value tau in the representation of H.
!>
```

*C*

```
!>          C is DOUBLE PRECISION array, dimension (LDC,N)
!>          On entry, the m by n matrix C.
!>          On exit, C is overwritten by the matrix H * C if SIDE = 'L',
!>          or C * H if SIDE = 'R'.
!>
```

*LDC*

```
!>          LDC is INTEGER
!>          The leading dimension of the array C. LDC >= (1,M).
!>
```

*WORK*

```
!>          WORK is DOUBLE PRECISION array, dimension
!>                      (N) if SIDE = 'L'
!>                      or (M) if SIDE = 'R'
!>          WORK is not referenced if H has order < 11.
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **119** of file **dlarfx.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.