SRC/zsteqr.f(3)            Library Functions Manual            SRC/zsteqr.f(3)

NAME
       SRC/zsteqr.f

SYNOPSIS
   Functions/Subroutines
       subroutine zsteqr (compz, n, d, e, z, ldz, work, info)
           ZSTEQR

Function/Subroutine Documentation
   subroutine zsteqr (character compz, integer n, double precision, dimension(
       * ) d, double precision, dimension( * ) e, complex*16, dimension( ldz,
       * ) z, integer ldz, double precision, dimension( * ) work, integer
       info)
       ZSTEQR

       Purpose:


            ZSTEQR computes all eigenvalues and, optionally, eigenvectors of a
            symmetric tridiagonal matrix using the implicit QL or QR method.
            The eigenvectors of a full or band complex Hermitian matrix can also
            be found if ZHETRD or ZHPTRD or ZHBTRD has been used to reduce this
            matrix to tridiagonal form.

       Parameters
           COMPZ

                     COMPZ is CHARACTER*1
                     = 'N':  Compute eigenvalues only.
                     = 'V':  Compute eigenvalues and eigenvectors of the original
                             Hermitian matrix.  On entry, Z must contain the
                             unitary matrix used to reduce the original matrix
                             to tridiagonal form.
                     = 'I':  Compute eigenvalues and eigenvectors of the
                             tridiagonal matrix.  Z is initialized to the identity
                             matrix.

           N

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

           D

                     D is DOUBLE PRECISION array, dimension (N)
                     On entry, the diagonal elements of the tridiagonal matrix.
                     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.
                     On exit, E has been destroyed.

           Z

                     Z is COMPLEX*16 array, dimension (LDZ, N)
                     On entry, if  COMPZ = 'V', then Z contains the unitary
                     matrix used in the reduction to tridiagonal form.
                     On exit, if INFO = 0, then if COMPZ = 'V', Z contains the
                     orthonormal eigenvectors of the original Hermitian matrix,
                     and if COMPZ = 'I', Z contains the orthonormal eigenvectors
                     of the symmetric tridiagonal matrix.
                     If COMPZ = 'N', then Z is not referenced.

           LDZ

                     LDZ is INTEGER
                     The leading dimension of the array Z.  LDZ >= 1, and if
                     eigenvectors are desired, then  LDZ >= max(1,N).

           WORK

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

           INFO

                     INFO is INTEGER
                     = 0:  successful exit
                     < 0:  if INFO = -i, the i-th argument had an illegal value
                     > 0:  the algorithm has failed to find all the eigenvalues in
                           a total of 30*N iterations; if INFO = i, then i
                           elements of E have not converged to zero; on exit, D
                           and E contain the elements of a symmetric tridiagonal
                           matrix which is unitarily similar to the original
                           matrix.

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Definition at line 131 of file zsteqr.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

LAPACK                          Version 3.12.0                 SRC/zsteqr.f(3)