LARFX - 5.2 English - 68552

LARFX applies an elementary reflector to a general rectangular matrix,

with loop unrolling when the reflector has order ≤ 10.

Purpose:

  LARFX 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**T

  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.

Parameters:

• SIDE – [in]

  SIDE is CHARACTER*1

  = ‘L’: form H * C

  = ‘R’: form C * H

• M – [in]

  M is INTEGER

  The number of rows of the matrix C.

• N – [in]

  N is INTEGER

  The number of columns of the matrix C.

• V – [in]

  V is REAL array, dimension (M) if SIDE = ‘L’ or (N) if SIDE = ‘R’

  The vector v in the representation of H.

• TAU – [in]

  TAU is REAL

  The value tau in the representation of H.

• C – [inout]

  C is REAL 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 – [in]

  LDC is INTEGER

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

• WORK – [out]

  WORK is REAL array, dimension (N) if SIDE = ‘L’ or (M) if SIDE = ‘R’

  WORK is not referenced if H has order < 11.