# dlarfx.f man page

dlarfx.f —

## Synopsis

### Functions/Subroutines

subroutinedlarfx(SIDE, M, N, V, TAU, C, LDC, WORK)DLARFXapplies an elementary reflector to a general rectangular matrix, with loop unrolling when the reflector has order ≤ 10.

## Function/Subroutine Documentation

### subroutine dlarfx (characterSIDE, integerM, integerN, double precision, dimension( * )V, double precisionTAU, double precision, dimension( ldc, * )C, integerLDC, 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. LDA >= (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.

**Date:**

September 2012

Definition at line 121 of file dlarfx.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

dlarfx(3) is an alias of dlarfx.f(3).