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zheevd() void zheevd ( char  jobz, char  uplo, int  n, int  lda, doublecomplex  a[], double  w[], doublecomplex  work[], int  lwork, double  rwork[], int  lrwork, int  iwork[], int  liwork, int *  info  ) (Divide and conquer driver) Eigenvalues and eigenvectors of a Hermitian matrix Purpose This routine computes all eigenvalues and, optionally, eigenvectors of a Hermitian matrix A. If only eigenvalues are desired, it uses a QL or QR method. If eigenvectors are also desired, it uses a divide and conquer algorithm. Parameters [in] jobz = 'N': Compute eigenvalues only. = 'V': Compute eigenvalues and eigenvectors. [in] uplo = 'U': Upper triangle of A is stored. = 'L': Lower triangle of A is stored. [in] n Order of the matrix A. (n >= 0) (If n = 0, returns without computation) [in] lda The leading dimension of the array a[][]. (lda >= max(1,n)) [in,out] a[][] Array a[la][lda] (la >= n) [in] The Hermitian matrix A. If uplo = 'U', the leading n x n upper triangular part of a[][] contains the upper triangular part of the matrix A. If uplo = 'L', the leading n x n lower triangular part of a[][] contains the lower triangular part of the matrix A. [out] jobz = 'V': If info = 0, a[][] contains the orthonormal eigenvectors of the matrix A.   jobz = 'N': The lower triangle (if uplo = 'L') or the upper triangle (if uplo = 'U') of a[][], including the diagonal, is destroyed. [out] w[] Array w[lw] (lw >= n) If info = 0, the eigenvalues in ascending order. [out] work[] Array work[lwork] Complex work array. On exit, if info = 0, work[0] returns the optimal lwork. [in] lwork The size of work[]. (lrwork >= 1 (if n <= 1), n + 1 (if jobz = 'N'), n^2 + 2*n (if jobz = 'V')) If lwork = -1, then a workspace query is assumed. The routine only calculates the optimal sizes of the work[], rwork[] and iwork[] arrays, and returns these values in work[0], rwork[0] and iwork[0]. [out] rwork[] Array rwork[lrwork] Work array. On exit, if info = 0, rwork[0] returns the optimal lwork. [in] lrwork The size of rwork[]. (lrwork >= 1 (if n <= 1), n (if jobz = 'N'), 2*n^2 + 5*n + 1 (if jobz = 'V')) If lrwork = -1, then a workspace query is assumed. The routine only calculates the optimal sizes of the work[], rwork[] and iwork[] arrays, and returns these values in work[0], rwork[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 sizes of the work[], rwork[] and iwork[] arrays, and returns these values in work[0], rwork[0] and iwork[0]. [out] info = 0: Successful exit = -1: The argument jobz had an illegal value (jobz != 'V' nor 'N') = -2: The argument uplo had an illegal value (uplo != 'U' nor 'L') = -3: The argument n had an illegal value (n < 0) = -4: The argument lda had an illegal value (lda < max(1, n)) = -8: The argument lwork had an illegal value (lwork too small) = -10: The argument lrwork had an illegal value (lrwork too small) = -12: The argument liwork had an illegal value (liwork too small) = i > 0: The algorithm failed to converge; i off-diagonal elements of an intermediate tridiagonal form did not converge to zero Reference LAPACK