On exit: if
${\mathbf{LBLOCK}}=\mathrm{.TRUE.}$,
NBLOCK contains the number of diagonal blocks in the Jacobian matrix permuted to block lower triangular form. If
${\mathbf{NBLOCK}}=1$ then on subsequent runs of a similar problem
LBLOCK should be set to .FALSE. in the call to
D02NUF.
If ${\mathbf{LBLOCK}}=\mathrm{.FALSE.}$, ${\mathbf{NBLOCK}}=1$.