DSTEV (3) Linux Manual Page

dstev.f –

Synopsis

Functions/Subroutines

subroutine dstev (JOBZ, N, D, E, Z, LDZ, WORK, INFO)
DSTEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER matrices

Function/Subroutine Documentation

subroutine dstev (characterJOBZ, integerN, double precision, dimension( * )D, double precision, dimension( * )E, double precision, dimension( ldz, * )Z, integerLDZ, double precision, dimension( * )WORK, integerINFO)

DSTEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER matrices

Purpose:

 DSTEV computes all eigenvalues and, optionally, eigenvectors of a

 real symmetric tridiagonal matrix A.

 

Parameters:

JOBZ

 JOBZ is CHARACTER*1

 = ‘N’: Compute eigenvalues only;

 = ‘V’: Compute eigenvalues and eigenvectors.

N

 N is INTEGER

 The order of the matrix. N >= 0.

D

 D is DOUBLE PRECISION array, dimension (N)

 On entry, the n diagonal elements of the tridiagonal matrix

 A.

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

E

 E is DOUBLE PRECISION array, dimension (N-1)

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

 matrix A, stored in elements 1 to N-1 of E.

 On exit, the contents of E are destroyed.

Z

 Z is DOUBLE PRECISION array, dimension (LDZ, N)

 If JOBZ = ‘V’, then if INFO = 0, Z contains the orthonormal

 eigenvectors of the matrix A, with the i-th column of Z

 holding the eigenvector associated with D(i).

 If JOBZ = ‘N’, then Z is not referenced.

LDZ

 LDZ is INTEGER

 The leading dimension of the array Z. LDZ >= 1, and if

 JOBZ = ‘V’, LDZ >= max(1,N).

WORK

 WORK is DOUBLE PRECISION array, dimension (max(1,2*N-2))

 If JOBZ = ‘N’, WORK is not referenced.

INFO

 INFO is INTEGER

 = 0: successful exit

 < 0: if INFO = -i, the i-th argument had an illegal value

 > 0: if INFO = i, the algorithm failed to converge; i

 off-diagonal elements of E did not converge to zero.

 

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

November 2011

Definition at line 117 of file dstev.f.

Author

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