Zgbcon Zgbtrf Zgbtrs Zgecon Zgetrf Zgetri Zgetrs Zgtcon Zgttrf Zgttrs Zspcon Zsptrf Zsptri Zsptrs Zsycon Zsytrf Zsytri Zsytrs

Zgttrs() Sub Zgttrs ( Trans As  String, N As  Long, Dl() As  Complex, D() As  Complex, Du() As  Complex, Du2() As  Complex, IPiv() As  Long, B() As  Complex, Info As  Long, Optional Nrhs As  Long = 1  ) Solution to LU factorized system of linear equations AX = B, ATX = B or AHX = B for a complex tridiagonal matrix Purpose This routine solves one of the system of equations A * X = B, A^T * X = B or A^H * X = B with a tridiagonal matrix A using the LU factorization computed by Zgttrf. Parameters [in] Trans Specifies the form of the system of equations: = "N": A * X = B. (no transpose) = "T": A^T * X = B. (transpose) = "C": A^H * X = B. (conjugate transpose) [in] N Order of the matrix A. (N >= 0) (If N = 0, returns without computation) [in] Dl() Array Dl(LDl - 1) (LDl >= N - 1) N-1 multipliers that define the matrix L from the LU factorization of A as computed by Dgttrf. [in] D() Array D(LD - 1) (LD >= N) N diagonal elements of the upper triangular matrix U from the LU factorization of A. [in] Du() Array Du(LDu - 1) (LDu >= N - 1) N-1 elements of the first super-diagonal of U. [in] Du2() Array Du2(LDu2 - 1) (LDu2 >= N - 2) N-2 elements of the second super-diagonal of U. [in] IPiv() Array IPiv(LIPiv - 1) (LIPiv >= N) Pivot indices; for 1 <= i <= N, row i of the matrix was interchanged with row IPiv(i-1). IPiv(i-1) will always be either i or i+1; IPiv(i-1) = i indicates a row interchange was not required. [in,out] B() Array B(LB1 - 1, LB2 - 1) (LB1 >= max(1, N), LB2 >= Nrhs) (2D array) or B(LB - 1) (LB >= max(1, N), Nrhs = 1) (1D array) [in] N x Nrhs matrix of right hand side matrix B. [out] If Info = 0, the N x Nrhs solution matrix X. [out] Info = 0: Successful exit. = -1: The argument Trans had an illegal value. (Trans <> "N", "T" nor "C") = -2: The argument N had an illegal value. (N < 0) = -3: The argument Dl() is invalid. = -4: The argument D() is invalid. = -5: The argument Du() is invalid. = -6: The argument Du2() is invalid. = -7: The argument IPiv() is invalid. = -8: The argument B() is invalid. = -10: The argument Nrhs had an illegal value. (Nrhs < 0) [in] Nrhs (Optional) Number of right hand sides, i.e., number of columns of the matrix B. (Nrhs >= 0) (If Nrhs = 0, returns without computation) (default = 1) Reference LAPACK Example Program See example of Zgttrf.