DLARFX (3lapack)

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.