DLARFY applies an elementary reflector, or Householder matrix, H,
 to an n x n symmetric matrix C, from both the left and the right.
 H is represented in the form
    H = I - tau * v * v'
 where  tau  is a scalar and  v  is a vector.
 If  tau  is  zero, then  H  is taken to be the unit matrix.

UPLO

          UPLO is CHARACTER*1
          Specifies whether the upper or lower triangular part of the
          symmetric matrix C is stored.
          = 'U':  Upper triangle
          = 'L':  Lower triangle

N

          N is INTEGER
          The number of rows and columns of the matrix C.  N >= 0.

V

          V is DOUBLE PRECISION array, dimension
                  (1 + (N-1)*abs(INCV))
          The vector v as described above.

INCV

          INCV is INTEGER
          The increment between successive elements of v.  INCV must
          not be zero.

TAU

          TAU is DOUBLE PRECISION
          The value tau as described above.

C

          C is DOUBLE PRECISION array, dimension (LDC, N)
          On entry, the matrix C.
          On exit, C is overwritten by H * C * H'.

LDC

          LDC is INTEGER
          The leading dimension of the array C.  LDC >= max( 1, N ).

WORK

          WORK is DOUBLE PRECISION array, dimension (N)

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

December 2016