1SSTEV(1)              LAPACK driver routine (version 3.1)             SSTEV(1)
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NAME

6       SSTEV - all eigenvalues and, optionally, eigenvectors of a real symmet‐
7       ric tridiagonal matrix A
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SYNOPSIS

10       SUBROUTINE SSTEV( JOBZ, N, D, E, Z, LDZ, WORK, INFO )
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12           CHARACTER     JOBZ
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14           INTEGER       INFO, LDZ, N
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16           REAL          D( * ), E( * ), WORK( * ), Z( LDZ, * )
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PURPOSE

19       SSTEV computes all eigenvalues and, optionally, eigenvectors of a  real
20       symmetric tridiagonal matrix A.
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ARGUMENTS

24       JOBZ    (input) CHARACTER*1
25               = 'N':  Compute eigenvalues only;
26               = 'V':  Compute eigenvalues and eigenvectors.
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28       N       (input) INTEGER
29               The order of the matrix.  N >= 0.
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31       D       (input/output) REAL array, dimension (N)
32               On  entry, the n diagonal elements of the tridiagonal matrix A.
33               On exit, if INFO = 0, the eigenvalues in ascending order.
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35       E       (input/output) REAL array, dimension (N-1)
36               On entry, the (n-1) subdiagonal  elements  of  the  tridiagonal
37               matrix  A, stored in elements 1 to N-1 of E.  On exit, the con‐
38               tents of E are destroyed.
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40       Z       (output) REAL array, dimension (LDZ, N)
41               If JOBZ = 'V', then if INFO = 0,  Z  contains  the  orthonormal
42               eigenvectors of the matrix A, with the i-th column of Z holding
43               the eigenvector associated with D(i).  If JOBZ = 'N', then Z is
44               not referenced.
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46       LDZ     (input) INTEGER
47               The  leading dimension of the array Z.  LDZ >= 1, and if JOBZ =
48               'V', LDZ >= max(1,N).
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50       WORK    (workspace) REAL array, dimension (max(1,2*N-2))
51               If JOBZ = 'N', WORK is not referenced.
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53       INFO    (output) INTEGER
54               = 0:  successful exit
55               < 0:  if INFO = -i, the i-th argument had an illegal value
56               > 0:  if INFO = i, the algorithm failed  to  converge;  i  off-
57               diagonal elements of E did not converge to zero.
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61 LAPACK driver routine (version 3.N1o)vember 2006                        SSTEV(1)