Dgbcon Dgbtrf Dgbtrs Dgecon Dgetrf Dgetri Dgetrs Dgtcon Dgttrf Dgttrs

Dgecon() Sub Dgecon ( Norm As  String, N As  Long, A() As  Double, ANorm As  Double, RCond As  Double, Info As  Long  ) Condition number of a general matrix Purpose This routine estimates the reciprocal of the condition number of a general real matrix A, in either the 1-norm or the infinity-norm, using the LU factorization computed by Dgetrf, Dgesv or Dgesvx. An estimate is obtained for norm(inv(A)), and 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] N Order of the matrix A. (N >= 0) (If N = 0, returns RCond = 1) [in] A() Array A(LA1 - 1, LA2 - 1) (LA1 >= N, LA2 >= N) Factors L and U from the factorization A = P*L*U as computed by Dgetrf, Dgesv or Dgesvx. [in] ANorm Norm = "1" or "O": The 1-norm of the original matrix A (ANorm >= 0) Norm = "I": The infinity-norm of the original matrix A (ANorm >= 0) [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 N had an illegal value. (N < 0) = -3: The argument A() is invalid. = -4: The argument ANorm had an illegal value. (ANorm < 0) Reference LAPACK Example Program See example of Dgesv.