# zlarz.f man page

zlarz.f —

## Synopsis

### Functions/Subroutines

subroutinezlarz(SIDE, M, N, L, V, INCV, TAU, C, LDC, WORK)ZLARZapplies an elementary reflector (as returned by stzrzf) to a general matrix.

## Function/Subroutine Documentation

### subroutine zlarz (characterSIDE, integerM, integerN, integerL, complex*16, dimension( * )V, integerINCV, complex*16TAU, complex*16, dimension( ldc, * )C, integerLDC, complex*16, dimension( * )WORK)

**ZLARZ** applies an elementary reflector (as returned by stzrzf) to a general matrix.

**Purpose:**

```
ZLARZ 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 complex scalar and v is a complex vector.
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.
H is a product of k elementary reflectors as returned by ZTZRZF.
```

**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.
```

*L*

```
L is INTEGER
The number of entries of the vector V containing
the meaningful part of the Householder vectors.
If SIDE = 'L', M >= L >= 0, if SIDE = 'R', N >= L >= 0.
```

*V*

```
V is COMPLEX*16 array, dimension (1+(L-1)*abs(INCV))
The vector v in the representation of H as returned by
ZTZRZF. V is not used if TAU = 0.
```

*INCV*

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

*TAU*

```
TAU is COMPLEX*16
The value tau in the representation of H.
```

*C*

```
C is COMPLEX*16 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*16 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.

**Date:**

September 2012

**Contributors:**

A. Petitet, Computer Science Dept., Univ. of Tenn., Knoxville, USA

**Further Details:**

Definition at line 148 of file zlarz.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

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