Ztbcon Ztbtrs Ztpcon Ztptri Ztptrs Ztrcon Ztrtri Ztrtrs

Ztbcon() Sub Ztbcon ( Norm As  String, Uplo As  String, Diag As  String, N As  Long, Kd As  Long, Ab() As  Complex, RCond As  Double, Info As  Long  ) Condition number of a complex triangular band matrix Purpose This routine estimates the reciprocal of the condition number of a triangular band matrix A, in either the 1-norm or the infinity-norm. The norm of A is computed and an estimate is obtained for norm(inv(A)), then the reciprocal of the condition number is computed as RCond = 1 / (norm(A) * norm(inv(A))). Parameters [in] Norm Specifies whether the 1-norm condition number or the infinity-norm condition number is required: = "1" or "O": 1-norm. = "I": Infinity-norm. [in] Uplo = "U": A is upper triangular. = "L": A is lower triangular. [in] Diag = "N": A is non-unit triangular. = "U": A is unit triangular. (Diagonal elements of Ab() are not referenced and are assumed to be 1) [in] N Order of the matrix A. (N >= 0) (If N = 0, returns RCond = 1) [in] Kd Number of super-diagonals or sub-diagonals of the triangular band matrix A. (Kd >= 0) [in] Ab() Array Ab(LAb1 - 1, LAb2 - 1) (LAb1 >= Kd + 1, LAb2 >= N) N x N triangular band matrix A in Kd+1 x N symmetric band matrix form. Upper or lower part is to be stored in accordance with Uplo. [out] RCond The reciprocal of the condition number of the matrix A, computed as RCond = 1/(norm(A) * norm(inv(A))). [out] Info = 0: Successful exit. = -1: The argument Norm had an illegal value. (Norm <> "1", "O" nor "I") = -2: The argument Uplo had an illegal value. (Uplo <> "U" nor "L") = -3: The argument Diag had an illegal value. (Diag <> "N" nor "U") = -4: The argument N had an illegal value. (N < 0) = -5: The argument Kd had an illegal value. (Kd < 0) = -6: The argument Ab() is invalid. Reference LAPACK Example Program See example of Ztbtrs.