Dgebak Dgebal Dgehrd Dhsein Dhseqr Dorghr Dormhr Dtrevc3 Dtrexc Dtrsen Dtrsna Dtrsyl

Dorghr() Sub Dorghr ( N As  Long, Ilo As  Long, Ihi As  Long, A() As  Double, Tau() As  Double, Info As  Long  ) Generates a transform matrix to Hessenberg form Purpose This routine generates a real orthogonal matrix Q which is defined as the product of Ihi-Ilo elementary reflectors of order N, as returned by Dgehrd. Q = H(Ilo) H(Ilo+1) . . . H(Ihi-1). Parameters [in] N Order of the matrix A. (N >= 0) (If N = 0, returns without computation) [in] Ilo [in] Ihi Ilo and Ihi must have the same values as in the previous call of Dgehrd. Q is equal to the unit matrix except in the submatrix Q(Ilo+1〜Ihi, Ilo+1〜Ihi). (1 <= Ilo <= Ihi <= N, if N > 0. Ilo = 1 and Ihi = 0, if N = 0) [in,out] A() Array A(LA1 - 1, LA2 - 1) (LA1 >= N, LA2 >= N) [in] The vectors which define the elementary reflectors, as returned by Dgehrd. [out] The N x N orthogonal matrix Q. [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 Dgehrd. [out] Info = 0: Successful exit. = -1: The argument N had an illegal value. (N < 0) = -2: The argument Ilo had an illegal value. (Ilo < 1 or Ilo > N) = -3: The argument Ihi had an illegal value. (Ihi < min(Ilo, N) or Ihi > N) = -4: The argument A() is invalid. = -5: The argument Tau() is invalid. Reference LAPACK Example Program See examples of Dtrevc3.