RT(3F)

NAME
     RT, SRT -  EISPACK routine.  This subroutine calls the recommended
     sequence of subroutines from the eigensystem subroutine package (EISPACK)
     to find the eigenvalues and eigenvectors (if desired) of a special REAL
     TRIDIAGONAL matrix.


SYNOPSYS
          subroutine  rt(nm, n, a, w, matz, z, fv1, ierr)
          integer          nm, n, matz, ierr
          double precision a(nm,3), w(n), z(nm n), fv1(n)

          subroutine srt(nm, n, a, w, matz, z, fv1, ierr)
          integer          nm, n, matz, ierr
          real             a(nm,3), w(n), z(nm n), fv1(n)



DESCRIPTION
     On Input

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

     N is the order of the matrix  A.

     A contains the special real tridiagonal matrix in its first three
     columns.  The subdiagonal elements are stored in the last  N-1  positions
     of the first column, the diagonal elements in the second column, and the
     superdiagonal elements in the first  N-1  positions of the third column.
     elements  A(1,1)  and  A(N,3)  are arbitrary.

     MATZ is an integer variable set equal to zero if only eigenvalues are
     desired.  Otherwise it is set to any non-zero integer for both
     eigenvalues and eigenvectors.  On Output

     W contains the eigenvalues in ascending order.

     Z contains the eigenvectors if MATZ is not zero.

     IERR is an integer output variable set equal to an error completion code
     described in section 2B of the documentation.  The normal completion code
     is zero.

     FV1 is a temporary storage array. Questions and comments should be
     directed to B. S. Garbow, APPLIED MATHEMATICS DIVISION, ARGONNE NATIONAL
     LABORATORY