# slarzb.f man page

slarzb.f

## Synopsis

### Functions/Subroutines

subroutine slarzb (SIDE, TRANS, DIRECT, STOREV, M, N, K, L, V, LDV, T, LDT, C, LDC, WORK, LDWORK)
SLARZB applies a block reflector or its transpose to a general matrix.

## Function/Subroutine Documentation

### subroutine slarzb (character SIDE, character TRANS, character DIRECT, character STOREV, integer M, integer N, integer K, integer L, real, dimension( ldv, * ) V, integer LDV, real, dimension( ldt, * ) T, integer LDT, real, dimension( ldc, * ) C, integer LDC, real, dimension( ldwork, * ) WORK, integer LDWORK)

SLARZB applies a block reflector or its transpose to a general matrix.

Purpose:

``` SLARZB applies a real block reflector H or its transpose H**T to
a real distributed M-by-N  C from the left or the right.

Currently, only STOREV = 'R' and DIRECT = 'B' are supported.```
Parameters:

SIDE

```          SIDE is CHARACTER*1
= 'L': apply H or H**T from the Left
= 'R': apply H or H**T from the Right```

TRANS

```          TRANS is CHARACTER*1
= 'N': apply H (No transpose)
= 'C': apply H**T (Transpose)```

DIRECT

```          DIRECT is CHARACTER*1
Indicates how H is formed from a product of elementary
reflectors
= 'F': H = H(1) H(2) . . . H(k) (Forward, not supported yet)
= 'B': H = H(k) . . . H(2) H(1) (Backward)```

STOREV

```          STOREV is CHARACTER*1
Indicates how the vectors which define the elementary
reflectors are stored:
= 'C': Columnwise                        (not supported yet)
= 'R': Rowwise```

M

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

N

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

K

```          K is INTEGER
The order of the matrix T (= the number of elementary
reflectors whose product defines the block reflector).```

L

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

V

```          V is REAL array, dimension (LDV,NV).
If STOREV = 'C', NV = K; if STOREV = 'R', NV = L.```

LDV

```          LDV is INTEGER
The leading dimension of the array V.
If STOREV = 'C', LDV >= L; if STOREV = 'R', LDV >= K.```

T

```          T is REAL array, dimension (LDT,K)
The triangular K-by-K matrix T in the representation of the
block reflector.```

LDT

```          LDT is INTEGER
The leading dimension of the array T. LDT >= K.```

C

```          C is REAL array, dimension (LDC,N)
On entry, the M-by-N matrix C.
On exit, C is overwritten by H*C or H**T*C or C*H or C*H**T.```

LDC

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

WORK

`          WORK is REAL array, dimension (LDWORK,K)`

LDWORK

```          LDWORK is INTEGER
The leading dimension of the array WORK.
If SIDE = 'L', LDWORK >= max(1,N);
if SIDE = 'R', LDWORK >= max(1,M).```
Author:

Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Date:

December 2016

Contributors:

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

Further Details:

Definition at line 185 of file slarzb.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page slarzb(3) is an alias of slarzb.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK