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

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NAG Ltd.

December 2016