Ddisna Dopgtr Dopmtr Dorgtr Dormtr Dpteqr Dsbtrd Dsptrd Dstebz Dstedc Dstein Dstemr Dsteqr Dsterf Dsytrd

Dopgtr() Sub Dopgtr ( Uplo As  String, N As  Long, Ap() As  Double, Tau() As  Double, Q() As  Double, Info As  Long  ) Generates a transform matrix from a real symmetric matrix in packed form to tridiagonal form Purpose This routine generates a real orthogonal matrix Q which is defined as the product of N - 1 elementary reflectors of order N, as returned by Dsptrd. If Uplo = "U", Q = H(N-1) . . . H(2) H(1). If Uplo = "L", Q = H(1) H(2) . . . H(N-1). Parameters [in] Uplo = "U": Upper triangular packed storage used in previous call to Dsptrd. = "L": Lower triangular packed storage used in previous call to Dsptrd. [in] N Order of the matrix Q. (N >= 0) (If N = 0, returns without computation) [in] Ap() Array Ap(LAp - 1) (LAp >= N(N + 1)/2) The vectors which define the elementary reflectors, as returned by Dsptrd. [in] Tau() Array Tau(LTau - 1) (LTau >= N - 1) Tau(i) must contain the scalar factor of the elementary reflector H(i), as returned by Dsptrd. [out] Q() Array Q(LQ1 - 1, LQ2 - 1) (LQ1 >= N, LQ2 >= N) The n x n orthogonal matrix Q. [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. = -4: The argument Tau() is invalid. = -5: The argument Q() is invalid. Reference LAPACK