---
name: "dsterf"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/dsterf/3lapack"
---

# dsterf(3lapack)

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

## NAME

DSTERF - 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.