zlarfgp()

subroutine zlarfgp	(	integer	n,
		complex*16	alpha,
		complex*16, dimension( * )	x,
		integer	incx,
		complex*16	tau )

ZLARFGP generates an elementary reflector (Householder matrix) with non-negative beta.

Download ZLARFGP + dependencies [TGZ] [ZIP] [TXT]

Purpose:

!>
!> ZLARFGP generates a complex elementary reflector H of order n, such
!> that
!>
!>       H**H * ( alpha ) = ( beta ),   H**H * H = I.
!>              (   x   )   (   0  )
!>
!> where alpha and beta are scalars, beta is real and non-negative, and
!> x is an (n-1)-element complex vector.  H is represented in the form
!>
!>       H = I - tau * ( 1 ) * ( 1 v**H ) ,
!>                     ( v )
!>
!> where tau is a complex scalar and v is a complex (n-1)-element
!> vector. Note that H is not hermitian.
!>
!> If the elements of x are all zero and alpha is real, then tau = 0
!> and H is taken to be the unit matrix.
!> 

Parameters

[in]	N	!> N is INTEGER !> The order of the elementary reflector. !>
[in,out]	ALPHA	!> ALPHA is COMPLEX*16 !> On entry, the value alpha. !> On exit, it is overwritten with the value beta. !>
[in,out]	X	!> X is COMPLEX*16 array, dimension !> (1+(N-2)*abs(INCX)) !> On entry, the vector x. !> On exit, it is overwritten with the vector v. !>
[in]	INCX	!> INCX is INTEGER !> The increment between elements of X. INCX > 0. !>
[out]	TAU	!> TAU is COMPLEX*16 !> The value tau. !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.