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.