Four types of driver routines are provided for symmetric or Hermitian eigenproblems:

• a simple driver (name ending -EV), which computes all the eigenvalues and (optionally) the eigenvectors of a symmetric or Hermitian matrix A;

• an expert driver (name ending -EVX), which can compute either all or a selected subset of the eigenvalues and (optionally) the corresponding eigenvectors. If few enough eigenvalues or eigenvectors are desired, the expert driver is faster than the simple driver.

• A divide-and-conquer driver (name ending -EVD) solves the same problem as the simple driver. It is much faster than the simple driver for large matrices, but uses more workspace. The name divide-and-conquer refers to the underlying algorithm (see sections 2.4.4 and 3.4.3).

• A relatively robust representation (RRR) driver (name ending -EVR) computes all or (in a later release) a subset of the eigenvalues, and (optionally) eigenvectors. It is the fastest algorithm of all (except for a few cases), and uses the least workspace. The name RRR refers to the underlying algorithm (see sections 2.4.4 and 3.4.3).

Different driver routines are provided to take advantage of special structure or storage of the matrix A, as shown in Table 2.5.