# ssterf.f

## NAME

ssterf.f −

## SYNOPSIS

**Functions/Subroutines**

subroutine **ssterf** (N, D, E, INFO)

SSTERF

## Function/Subroutine Documentation

**subroutine ssterf (integerN, real, dimension( * )D, real, dimension( * )E, integerINFO)**

SSTERF

**Purpose:**

SSTERF computes all eigenvalues of a symmetric tridiagonal matrix

using the Pal-Walker-Kahan variant of the QL or QR algorithm.

**Parameters:**

*N*

N is INTEGER

The order of the matrix. N >= 0.

*D*

D is REAL array, dimension (N)

On entry, the n diagonal elements of the tridiagonal matrix.

On exit, if INFO = 0, the eigenvalues in ascending order.

*E*

E is REAL array, dimension (N-1)

On entry, the (n-1) subdiagonal elements of the tridiagonal

matrix.

On exit, E has been destroyed.

*INFO*

INFO is 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.

**Author:**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**

November 2011

Definition at line 87 of file ssterf.f.

## Author

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