dlarz-f(3)

dlarz.f –

Synopsis

Functions/Subroutines

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

Function/Subroutine Documentation

subroutine dlarz (characterSIDE, integerM, integerN, integerL, double precision, dimension( * )V, integerINCV, double precisionTAU, double precision, dimension( ldc, * )C, integerLDC, double precision, dimension( * )WORK)

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

Purpose:

 DLARZ 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.
 H is a product of k elementary reflectors as returned by DTZRZF.

Parameters:

SIDE

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

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

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

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

INCV

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

TAU

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

 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 >= max(1,M).

WORK

 WORK is DOUBLE PRECISION 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 146 of file dlarz.f.

Author

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