DSTERF(3F)DSTERF(3F)NAME
DSTERF - compute 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.
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