LARFY - 5.2 English - 68552

LARFY applies an elementary reflector, or Householder matrix, H,

to an n x n symmetric matrix C, from both the left and the right.

Purpose:

 LARFY 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.

Parameters:

• UPLO – [in]

  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 – [in]

  N is INTEGER

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

• V – [in]

  V is REAL array, dimension (1 + (N-1)*abs(INCV))

  The vector v as described above.

• INCV – [in]

  INCV is INTEGER

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

• TAU – [in]

  TAU is REAL

  The value tau as described above.

• C – [inout]

  C is REAL array, dimension (LDC, N)

  On entry, the matrix C. On exit, C is overwritten by H * C * H’.

• LDC – [in]

  LDC is INTEGER

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

• WORK – [out] WORK is REAL array, dimension (N)