Provided by: liblapack-doc_3.3.1-1_all

**NAME**

LAPACK-3 - computes all eigenvalues of a symmetric tridiagonal matrix using the Pal- Walker-Kahan variant of the QL or QR algorithm

**SYNOPSIS**

SUBROUTINE DSTERF( N, D, E, INFO ) INTEGER INFO, N DOUBLE PRECISION D( * ), E( * )

**PURPOSE**

DSTERF computes all eigenvalues of a symmetric tridiagonal matrix using the Pal-Walker- Kahan variant of the QL or QR algorithm.

**ARGUMENTS**

N (input) INTEGER The order of the matrix. N >= 0. D (input/output) DOUBLE PRECISION array, dimension (N) On entry, the n diagonal elements of the tridiagonal matrix. On exit, if INFO = 0, the eigenvalues in ascending order. E (input/output) DOUBLE PRECISION array, dimension (N-1) On entry, the (n-1) subdiagonal elements of the tridiagonal matrix. On exit, E has been destroyed. INFO (output) INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value > 0: the algorithm failed to find all of the eigenvalues in a total of 30*N iterations; if INFO = i, then i elements of E have not converged to zero. LAPACK routine (version 3.3.1) April 2011 DSTERF(3lapack)