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 vector. 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.