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) |