Compute the eigenvalues and eigenvectors of a real symmetric tridiagonal matrix. More...
Public Member Functions | |
subroutine | dsteqr (COMPZ, N, D, E, Z, LDZ, WORK, INFO) |
Compute the eigenvalues and eigenvectors of a real symmetric tridiagonal matrix.
The DSTEQR subroutine computes all eigenvalues and, optionally, eigenvectors of a real, symmetric, tridiagonal matrix. It uses the implicit QL or QR method to do so.
More information on DSTEQR can be found in the LAPACK documentation.
COMPZ | Specifies computation of eigenvectors ('V') or not ('N') |
N | Order of the matrix |
D | On entry, the diagonal elements. On exit, the eigenvalues in ascending order |
E | Off-diagonal elements on entry; destroyed on exit |
Z | On entry, if COMPZ = 'V', then Z is an N-by-N matrix. On exit, if COMPZ = 'V', Z contains the orthogonal matrix of eigenvectors |
LDZ | Leading dimension of Z as declared in the calling subroutine |
WORK | Work array, dimension (max(1, 2*N-2)) if COMPZ = 'V', (max(1, 1)) otherwise |
INFO | INFO = 0: successful exit. INFO = K: the algorithm failed to find all the eigenvalues, no eigenvectors or eigenvectors of order K have been found |
Definition at line 41 of file gjp_lapack.f90.
subroutine gjp_lapack::DSTEQR::dsteqr | ( | character | COMPZ, |
integer | N, | ||
real(dp), dimension(*) | D, | ||
real(dp), dimension(*) | E, | ||
real(dp), dimension(ldz, *) | Z, | ||
integer | LDZ, | ||
real(dp), dimension(*) | WORK, | ||
integer | INFO | ||
) |
Definition at line 41 of file gjp_lapack.f90.