In the intermediate state A is reduced to tridiagonal form. In compact storage format, the symmetric tridiagonal matrix is stored in T.
|DS_MAT_A||- problem matrix|
|DS_MAT_T||- symmetric tridiagonal matrix|
|DS_MAT_Q||- orthogonal/unitary transformation that reduces to tridiagonal form (intermediate step) or matrix of orthogonal eigenvectors, which is equal to X|
|0||- Implicit QR (_steqr)|
|1||- Multiple Relatively Robust Representations (_stevr)|
|2||- Divide and Conquer (_stedc)|
|3||- Block Divide and Conquer (real scalars only)|