Dpocon Dpotrf Dpotri Dpotrs Dppcon Dpptrf Dpptri Dpptrs Dsposv

Dpptri() Sub Dpptri ( Uplo As  String, N As  Long, Ap() As  Double, Info As  Long  ) Inverse of a symmetric positive definite matrix in packed form Purpose This routine computes the inverse of a real symmetric positive definite matrix A in packed form using the Cholesky factorization A = U^T*U or A = L*L^T computed by Dpptrf. Parameters [in] Uplo = "U": Upper triangular factor U is stored in Ap(). = "L": Lower triangular factor L is stored in Ap(). [in] N Order of the matrix A. (N >= 0) (If N = 0, returns without computation) [in] Ap() Array Ap(LAp - 1) (LAp >= N(N + 1)/2) [in] The triangular factor U or L in packed form from the Cholesky factorization A = U^T*U or A = L*L^T, as computed by Dpptrf. [out] If Info = 0, the upper or lower triangle of the (symmetric) inverse of A, overwriting the input factor U or L. [out] Info = 0: Successful exit. = -1: The argument Uplo had an illegal value. (Uplo <> "U" nor "L") = -2: The argument N had an illegal value. (N < 0) = -3: The argument Ap() is invalid. = i > 0: The i-th diagonal element of the factor U or L is zero, and the inverse could not be computed. Reference LAPACK Example Program Compute the inverse matrix of A, where A is symmetric positive definite and ( 2.2 -0.11 -0.32 ) A = ( -0.11 2.93 0.81 ) ( -0.32 0.81 2.37 ) Sub Ex_Dpptri() Const N = 3 Dim Ap(N * (N + 1) / 2) As Double, Info As Long Ap(0) = 2.2 Ap(1) = -0.11: Ap(3) = 2.93 Ap(2) = -0.32: Ap(4) = 0.81: Ap(5) = 2.37: Call Dpptrf("L", N, Ap(), Info) If Info = 0 Then Call Dpptri("L", N, Ap(), Info) Debug.Print "Inv(A) =" Debug.Print Ap(0) Debug.Print Ap(1), Ap(3) Debug.Print Ap(2), Ap(4), Ap(5) Debug.Print "Info =", Info End Sub Example Results Inv(A) = 0.463651335375572 1.10603849087679E-04 0.376908423331071 6.25649106339333E-02 -0.128801869057578 0.474409403096834 Info = 0