.TH SSTEV 1 "November 2006" " LAPACK driver routine (version 3.1) " " LAPACK driver routine (version 3.1) " .SH NAME SSTEV - all eigenvalues and, optionally, eigenvectors of a real symmetric tridiagonal matrix A .SH SYNOPSIS .TP 18 SUBROUTINE SSTEV( JOBZ, N, D, E, Z, LDZ, WORK, INFO ) .TP 18 .ti +4 CHARACTER JOBZ .TP 18 .ti +4 INTEGER INFO, LDZ, N .TP 18 .ti +4 REAL D( * ), E( * ), WORK( * ), Z( LDZ, * ) .SH PURPOSE SSTEV computes all eigenvalues and, optionally, eigenvectors of a real symmetric tridiagonal matrix A. .SH ARGUMENTS .TP 8 JOBZ (input) CHARACTER*1 = \(aqN\(aq: Compute eigenvalues only; .br = \(aqV\(aq: Compute eigenvalues and eigenvectors. .TP 8 N (input) INTEGER The order of the matrix. N >= 0. .TP 8 D (input/output) REAL array, dimension (N) On entry, the n diagonal elements of the tridiagonal matrix A. On exit, if INFO = 0, the eigenvalues in ascending order. .TP 8 E (input/output) REAL 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. .TP 8 Z (output) REAL array, dimension (LDZ, N) If JOBZ = \(aqV\(aq, 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 = \(aqN\(aq, then Z is not referenced. .TP 8 LDZ (input) INTEGER The leading dimension of the array Z. LDZ >= 1, and if JOBZ = \(aqV\(aq, LDZ >= max(1,N). .TP 8 WORK (workspace) REAL array, dimension (max(1,2*N-2)) If JOBZ = \(aqN\(aq, WORK is not referenced. .TP 8 INFO (output) INTEGER = 0: successful exit .br < 0: if INFO = -i, the i-th argument had an illegal value .br > 0: if INFO = i, the algorithm failed to converge; i off-diagonal elements of E did not converge to zero.