_dgecon _dgecov _dgels _dgesv _dlange _dlansy _dpocon _dposv _dsyev

_dgecon() void _dgecon ( char  norm, int  n, int  lda, double  a[], double  anorm, double *  rcond, double  work[], int  iwork[], int *  info  ) 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] lda Leading dimension of the two dimensional array a[][]. (lda >= max(1, n)) [in] a[][] Array a[la][lda] (la >= 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] work[] Array work[lwork] (lwork >= 4*n) Work array. [out] iwork[] Array iwork[liwork] (liwork >= n) Work array. [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 lda had an illegal value (lda < max(1, n)) = -5: The argument anorm had an illegal value (anorm < 0) Reference LAPACK