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dlarfgp.f(3) LAPACK dlarfgp.f(3)

NAME

dlarfgp.f -

SYNOPSIS

Functions/Subroutines


subroutine dlarfgp (N, ALPHA, X, INCX, TAU)
DLARFGP generates an elementary reflector (Householder matrix) with non-negatibe beta.

Function/Subroutine Documentation

subroutine dlarfgp (integerN, double precisionALPHA, double precision, dimension( * )X, integerINCX, double precisionTAU)

DLARFGP generates an elementary reflector (Householder matrix) with non-negatibe beta.

Purpose:


DLARFGP generates a real elementary reflector H of order n, such
that
H * ( alpha ) = ( beta ), H**T * H = I.
( x ) ( 0 )
where alpha and beta are scalars, beta is non-negative, and x is
an (n-1)-element real vector. H is represented in the form
H = I - tau * ( 1 ) * ( 1 v**T ) ,
( v )
where tau is a real scalar and v is a real (n-1)-element
vector.
If the elements of x are all zero, then tau = 0 and H is taken to be
the unit matrix.

Parameters:

N


N is INTEGER
The order of the elementary reflector.

ALPHA


ALPHA is DOUBLE PRECISION
On entry, the value alpha.
On exit, it is overwritten with the value beta.

X


X is DOUBLE PRECISION array, dimension
(1+(N-2)*abs(INCX))
On entry, the vector x.
On exit, it is overwritten with the vector v.

INCX


INCX is INTEGER
The increment between elements of X. INCX > 0.

TAU


TAU is DOUBLE PRECISION
The value tau.

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Definition at line 105 of file dlarfgp.f.

Author

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Tue Sep 25 2012 Version 3.4.2