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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( * )



     #include <sunperf.h>

     void dlarfg(int n, double *dalpha,  double  *dx,  int  incx,
               double *tau) ;

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.

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