dsbev dsbevd dsbevx dspev dspevd dspevx dstev dstevd dstevr dstevx dsyev dsyevd dsyevr dsyevx

dstevd() void dstevd ( char  jobz, int  n, double  d[], double  e[], int  ldz, double  z[], double  work[], int  lwork, int  iwork[], int  liwork, int *  info  ) (Divide and conquer driver) Eigenvalues and eigenvectors of a symmetric tridiagonal matrix Purpose This routine computes all eigenvalues and, optionally, eigenvectors of a real symmetric tridiagonal matrix. If eigenvectors are desired, it uses a divide and conquer algorithm. Parameters [in] jobz = 'N': Compute eigenvalues only. = 'V': Compute eigenvalues and eigenvectors. [in] n Order of the matrix A. (n >= 0) (If n = 0, returns without computation) [in,out] d[] Array d[ld] (ld >= n) [in] n diagonal elements of the symmetric tridiagonal matrix A. [out] If info = 0, the eigenvalues in ascending order. [in,out] e[] Array e[le] (le >= n - 1) [in] n - 1 subdiagonal elements of the symmetric tridiagonal matrix A stored in elements 0 to n - 2 of e[]. [out] The contents of e[] are destroyed. [in] ldz Leading dimension of the two dimensional array z[][]. (ldz >= 1 (jobz = 'N'), ldz >= max(1, n) (jobz = 'V')) [out] z[][] Array z[lz][ldz] (lz >= n) jobz = 'V': If info = 0, z[][] contains the orthonormal eigenvectors of the matrix A, with the i-th row of z[][] holding the eigenvector associated with d[i]. jobz = 'N': z[][] is not referenced. [out] work[] Array work[lwork] Work array. On exit, if info = 0, work[0] returns the optimal lwork. [in] lwork The size of work[]. (lwork >= 1 (if n <= 1), 1 (if jobz = 'N'), n^2 + 4*n + 1 (if jobz = 'V')) If lwork = -1, then a workspace query is assumed. The routine only calculates the optimal size of the work[] and iwork[] arrays, and returns these values in work[0] and iwork[0]. [out] iwork[] Array iwork[liwork] Integer work array. On exit, if info = 0, iwork[0] returns the optimal liwork. [in] liwork The size of iwork[]. (liwork >= 1 (if n <= 1), 1 (if jobz = 'N'), 5*n + 3 (if jobz = 'V')) If liwork = -1, then a workspace query is assumed. The routine only calculates the optimal size of the work[] and iwork[] arrays, and returns these values in work[0] and iwork[0]. [out] info = 0: Successful exit = -1: The argument jobz had an illegal value (jobz != 'V' nor 'N') = -2: The argument n had an illegal value (n < 0) = -5: The argument ldz had an illegal value (ldz too small) = -8: The argument lwork had an illegal value. (lwork too small) = -10: The argument liwork had an illegal value. (liwork too small) = i > 0: The algorithm failed to converge; i off-diagonal elements of e[] did not converge to zero Reference LAPACK