clarfg(3)

NAME

CLARFG - generate a complex elementary reflector H of or

der n, such that H' * ( alpha ) = ( beta ), H' * H = I

SYNOPSIS

SUBROUTINE CLARFG( N, ALPHA, X, INCX, TAU )
    INTEGER        INCX, N
    COMPLEX        ALPHA, TAU
    COMPLEX        X( * )

PURPOSE

CLARFG generates a complex elementary reflector H of order

n, such that H' * ( alpha ) = ( beta ), H' * H = I. (

x ) ( 0 )

where alpha and beta are scalars, with beta real, and x is

an (n-1)-element complex vector. H is represented in the form

H = I - tau * ( 1 ) * ( 1 v' ) ,

( v )

where tau is a complex scalar and v is a complex (n-1)-el

ement 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.

Otherwise 1 <= real(tau) <= 2 and abs(tau-1) <= 1 .

ARGUMENTS

N (input) INTEGER

The order of the elementary reflector.

ALPHA (input/output) COMPLEX

On entry, the value alpha. On exit, it is over

written with the value beta.

X (input/output) COMPLEX 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) COMPLEX

The value tau.

LAPACK version 3.0 15 June 2000

CLARFG(3)