DLARFG(1) LAPACK auxiliary routine (version 3.2) DLARFG(1)NAME
DLARFG - generates a real elementary reflector H of order n, such that
H * ( alpha ) = ( beta ), H' * H = I
SYNOPSIS
SUBROUTINE DLARFG( N, ALPHA, X, INCX, TAU )
INTEGER INCX, N
DOUBLE PRECISION ALPHA, TAU
DOUBLE PRECISION X( * )
PURPOSE
DLARFG generates a real elementary reflector H of order n, such that
( x ) ( 0 )
where alpha and beta are scalars, and x is an (n-1)-element real vec‐
tor. H is represented in the form
H = I - tau * ( 1 ) * ( 1 v' ) ,
( 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.
Otherwise 1 <= tau <= 2.
ARGUMENTS
N (input) INTEGER
The order of the elementary reflector.
ALPHA (input/output) DOUBLE PRECISION
On entry, the value alpha. On exit, it is overwritten with the
value beta.
X (input/output) DOUBLE PRECISION array, dimension
(1+(N-2)*abs(INCX)) On entry, the vector x. On exit, it is
overwritten with the vector v.
INCX (input) INTEGER
The increment between elements of X. INCX > 0.
TAU (output) DOUBLE PRECISION
The value tau.
LAPACK auxiliary routine (versioNovember 2008 DLARFG(1)
