DLARFG generates a real elementary reflector H of order n, such


 that


       H * ( alpha ) = ( beta ),   H**T * 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**T ) ,


                     ( 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.

N

          N is INTEGER


          The order of the elementary reflector.

ALPHA

          ALPHA is DOUBLE PRECISION


          On entry, the value alpha.


          On exit, it is overwritten with the value beta.

X

          X is DOUBLE PRECISION array, dimension


                         (1+(N-2)*abs(INCX))


          On entry, the vector x.


          On exit, it is overwritten with the vector v.

INCX

          INCX is INTEGER


          The increment between elements of X. INCX > 0.

TAU

          TAU is DOUBLE PRECISION


          The value tau.

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

November 2017