Zhbtrd Zhetrd Zhptrd Zpteqr Zstedc Zstein Zstemr Zsteqr Zungtr Zunmtr Zupgtr Zupmtr

Zungtr() Sub Zungtr ( Uplo As  String, N As  Long, A() As  Complex, Tau() As  Complex, Info As  Long  ) Generates a transform matrix from a complex Hermitian matrix to tridiagonal form Purpose This routine generates a complex unitary matrix Q which is defined as the product of N - 1 elementary reflectors of order N, as returned by Zhetrd. 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 triangle of A() contains elementary reflectors from Zhetrd. = "L": Lower triangle of A() contains elementary reflectors from Zhetrd. [in] N Order of the matrix Q. (N >= 0) (If N = 0, returns without computation) [in,out] A() Array A(LA1 - 1, LA2 - 1) (LA1 >= N, LA2 >= N) [in] The vectors which define the elementary reflectors, as returned by Zhetrd. [out] The N x N unitary matrix Q. [in] Tau() Array Tau(LTau - 1) (LTau >= N - 1) The scalar factors of the elementary reflectors, as returned by Zhetrd. [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 A() is invalid. = -4: The argument Tau() is invalid. Reference LAPACK Example Program See example of Zsteqr.