HTRIBK(3F)

NAME
     HTRIBK, SHTRIBK  -  EISPACK routine.  This subroutine forms the
     eigenvectors of a COMPLEX HERMITIAN matrix by back transforming those of
     the corresponding real symmetric tridiagonal matrix determined by
     HTRIDI.


SYNOPSYS
          subroutine  htribk(nm, n, ar, ai, tau, m, zr, zi)
          integer          nm, n, m
          double precision ar(nm,n),ai(nm,n),tau(2,n),zr(nm,m),zi(nm,m)

          subroutine shtribk(nm, n, ar, ai, tau, m, zr, zi)
          integer          nm, n, m
          real             ar(nm,n),ai(nm,n),tau(2,n),zr(nm,m),zi(nm,m)



DESCRIPTION
     On INPUT

     NM must be set to the row dimension of two-dimensional array parameters
     as declared in the calling program dimension statement.

     N is the order of the matrix.

     AR and AI contain information about the unitary trans- formations used in
     the reduction by  HTRIDI  in their full lower triangles except for the
     diagonal of AR.

     TAU contains further information about the transformations.

     M is the number of eigenvectors to be back transformed.

     ZR contains the eigenvectors to be back transformed in its first M
     columns.  On OUTPUT

     ZR and ZI contain the real and imaginary parts, respectively, of the
     transformed eigenvectors in their first M columns.  Note that the last
     component of each returned vector is real and that vector Euclidean norms
     are preserved.  Questions and comments should be directed to B. S.
     Garbow, APPLIED MATHEMATICS DIVISION, ARGONNE NATIONAL LABORATORY