><B>[Example]</B></A>

<P>
<B><FONT SIZE="+1">Purpose</FONT></B>
<PRE>
  To compute an orthogonal matrix Q and an orthogonal symplectic
  matrix U for a real regular 2-by-2 or 4-by-4 skew-Hamiltonian/
  Hamiltonian pencil a J B' J' B - b D with

        ( B11  B12 )      (  D11  D12  )      (  0  I  )
    B = (          ), D = (            ), J = (        ),
        (  0   B22 )      (   0  -D11' )      ( -I  0  )

  such that J Q' J' D Q and U' B Q keep block triangular form, but
  the eigenvalues are reor