dlarfg.f man page

dlarfg.f —

Synopsis

Functions/Subroutines

subroutine dlarfg (N, ALPHA, X, INCX, TAU)
DLARFG generates an elementary reflector (Householder matrix).

Function/Subroutine Documentation

subroutine dlarfg (integerN, double precisionALPHA, double precision, dimension( * )X, integerINCX, double precisionTAU)

DLARFG generates an elementary reflector (Householder matrix).

Purpose:

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.

Parameters:

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.

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Definition at line 107 of file dlarfg.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

dlarfg(3) is an alias of dlarfg.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK