---
name: "clarf1l.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/clarf1l.f"
---

# clarf1l.f(3)

## NAME

SRC/clarf1l.f

## SYNOPSIS

### Functions/Subroutines

subroutine **clarf1l** (side, m, n, v, incv, tau, c, ldc, work)\
 **CLARF1L** applies an elementary reflector to a general rectangular

## Function/Subroutine Documentation

### subroutine clarf1l (character side, integer m, integer n, complex, dimension( \* ) v, integer incv, complex tau, complex, dimension( ldc, \* ) c, integer ldc, complex, dimension( \* ) work)

**CLARF1L** applies an elementary reflector to a general rectangular

**Purpose:**

```
!>
!> CLARF1L applies a complex elementary reflector H to a complex m by n matrix
!> C, from either the left or the right. H is represented in the form
!>
!>       H = I - tau * v * v**H
!>
!> where tau is a real scalar and v is a real vector assuming v(lastv) = 1,
!> where lastv is the last non-zero element.
!>
!> If tau = 0, then H is taken to be the unit matrix.
!>
!> To apply H**H (the conjugate transpose of H), supply conjg(tau) instead
!> tau.
!>
```

**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 COMPLEX array, dimension
!>                     (1 + (M-1)*abs(INCV)) if SIDE = 'L'
!>                  or (1 + (N-1)*abs(INCV)) if SIDE = 'R'
!>          The vector v in the representation of H. V is not used if
!>          TAU = 0.
!>
```

*INCV*

```
!>          INCV is INTEGER
!>          The increment between elements of v. INCV > 0.
!>
```

*TAU*

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

*C*

```
!>          C is COMPLEX 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 >= max(1,M).
!>
```

*WORK*

```
!>          WORK is COMPLEX array, dimension
!>                         (N) if SIDE = 'L'
!>                      or (M) if SIDE = 'R'
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **128** of file **clarf1l.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.