_dgecon _dgecov _dgels _dgesv _dlange _dlansy _dpocon _dposv _dsyev

_dpocon() void _dpocon ( char  uplo, int  n, int  lda, double  a[], double  anorm, double *  rcond, double  work[], int  iwork[], int *  info  ) Condition number of a symmetric positive definite matrix Purpose This routine estimates the reciprocal of the condition number (in the 1-norm) of a real symmetric positive definite matrix using the Cholesky factorization A = U^T*U or A = L*L^T computed by dpotrf. An estimate is obtained for norm(inv(A)), and the reciprocal of the condition number is computed as rcond = 1 / (anorm * norm(inv(A))). Parameters [in] uplo Specifies whether the factor U or L is stored. = 'U': Upper triangular factor U from the Cholesky factorization A = U^T*U. = 'L': Lower triangular factor L from the Cholesky factorization A = L*L^T. [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) The triangular factor U or L from the Cholesky factorization A = U^T*U or A = L*L^T, as computed by dpotrf. [in] anorm The 1-norm (or infinity-norm) of the symmetric matrix A. (anorm >= 0) [out] rcond The reciprocal of the condition number of the matrix A, computed as rcond = 1/(anorm * ainvnm), where ainvnm is an estimate of the 1-norm of inv(A) computed in this routine. [out] work[] Array work[lwork] (lwork >= 3*n) Work array. [out] iwork[] Array iwork[liwork] (liwork >= n) Work array. [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 lda had an illegal value (lda < max(1, n)) = -5: The argument anorm had an illegal value (anorm < 0) Reference LAPACK