slarfgp.f3
Usage
Functions/Subroutines
subroutine slarfgp (n, alpha, x, incx, tau)
SLARFGP generates an elementary reflector (Householder matrix) with non-negative beta.
Function/Subroutine Documentation
subroutine slarfgp (integer n, real alpha, real, dimension( * ) x, integer incx, real tau)
SLARFGP generates an elementary reflector (Householder matrix) with non-negative beta.
Purpose:
!> !> SLARFGP 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, 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**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. !>
Parameters
N
!> N is INTEGER !> The order of the elementary reflector. !>
ALPHA
!> ALPHA is REAL !> On entry, the value alpha. !> On exit, it is overwritten with the value beta. !>
X
!> X is REAL 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 REAL !> The value tau. !>
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Definition at line 103 of file slarfgp.f.
Releases
4 releases since Debian 7 (Wheezy); the text changed 3 times.