Calculates the eigenvalues of a 3 x 3 real symmetric matrix. The eigenvalues calculated are in decreasing order. Only the diagonal and lower triangular part of the matrix is accessed.
Reference: https://en.wikipedia.org/wiki/Eigenvalue_algorithm#cite_note-Smith-12
See also David Eberly's notes and implementation at https://www.geometrictools.com/Documentation/RobustEigenSymmetric3x3.pdf
| Type | Intent | Optional | Attributes | Name | ||
|---|---|---|---|---|---|---|
| real(kind=rp), | intent(in), | dimension(3,3) | :: | a | ||
| real(kind=rp), | intent(out), | dimension(3) | :: | ev |