DSTEV(3)       LAPACK routine of NEC Numeric Library Collection       DSTEV(3)



NAME
       DSTEV

SYNOPSIS
       SUBROUTINE DSTEV (JOBZ, N, D, E, Z, LDZ, WORK, INFO)



PURPOSE
            DSTEV computes all eigenvalues and, optionally, eigenvectors of a
            real symmetric tridiagonal matrix A.




ARGUMENTS
           JOBZ      (input)
                     JOBZ is CHARACTER*1
                     = 'N':  Compute eigenvalues only;
                     = 'V':  Compute eigenvalues and eigenvectors.

           N         (input)
                     N is INTEGER
                     The order of the matrix.  N >= 0.

           D         (input/output)
                     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         (input/output)
                     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         (output)
                     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       (input)
                     LDZ is INTEGER
                     The leading dimension of the array Z.  LDZ >= 1, and if
                     JOBZ = 'V', LDZ >= max(1,N).

           WORK      (output)
                     WORK is DOUBLE PRECISION array, dimension (max(1,2*N-2))
                     If JOBZ = 'N', WORK is not referenced.

           INFO      (output)
                     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.



LAPACK routine                  31 October 2017                       DSTEV(3)