redhat man page for dlarfg

DLARFG(l)								 )								 DLARFG(l)

NAME
       DLARFG - generate 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 H * ( alpha ) = ( beta ), H' * H = I.	    (	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.

LAPACK version 3.0						   15 June 2000 							 DLARFG(l)