dlarfp(l) - Linux man page

Name

DLARFP - generates a real elementary reflector H of order n, such that H * ( alpha ) = ( beta ), H' * H = I

Synopsis

SUBROUTINE DLARFP(

N, ALPHA, X, INCX, TAU )

INTEGER

INCX, N

DOUBLE

PRECISION ALPHA, TAU

DOUBLE

PRECISION X( * )

Purpose

DLARFP generates a real elementary reflector H of order n, such that ( x ) ( 0 )
where alpha and beta are scalars, beta is non-negative, 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.