NAME

DLARFX - applie a real elementary reflector H to a real m by n matrix C, from either the left or the right

SYNOPSIS

SUBROUTINE DLARFX(
SIDE, M, N, V, TAU, C, LDC, WORK )

CHARACTER SIDE

INTEGER LDC, M, N

DOUBLE PRECISION TAU

DOUBLE PRECISION C( LDC, ∗ ), V( ∗ ), WORK( ∗ )

PURPOSE

DLARFX applies a real elementary reflector H to a real m by n matrix C, from either the left or the right. H is represented in the form
 
      H = I - tau ∗ v ∗ v’
 
where tau is a real scalar and v is a real vector.
 
If tau = 0, then H is taken to be the unit matrix
 
This version uses inline code if H has order < 11.
 

ARGUMENTS

SIDE    (input) CHARACTER∗1
= ’L’: form  H ∗ C
= ’R’: form  C ∗ H

M       (input) INTEGER
The number of rows of the matrix C.

N       (input) INTEGER
The number of columns of the matrix C.

V       (input) DOUBLE PRECISION array, dimension (M) if SIDE = ’L’
or (N) if SIDE = ’R’ The vector v in the representation of H.

TAU     (input) DOUBLE PRECISION
The value tau in the representation of H.

C       (input/output) DOUBLE PRECISION array, dimension (LDC,N)
On entry, the m by n matrix C. On exit, C is overwritten by the matrix H ∗ C if SIDE = ’L’, or C ∗ H if SIDE = ’R’.

LDC     (input) INTEGER
The leading dimension of the array C. LDA >= (1,M).

WORK    (workspace) DOUBLE PRECISION array, dimension
(N) if SIDE = ’L’ or (M) if SIDE = ’R’ WORK is not referenced if H has order < 11.

  —  LAPACK version 2.0  —  08 October 1994