function ib = bandwidth ( element_num, element_node, ...
  node_num, node_p_variable, node_u_variable, node_v_variable )

%% BANDWIDTH determines the bandwidth of the coefficient matrix.
%
%  Discussion:
%
%    We take the bandwidth to be the maximum difference between the
%    indices of two variables associated with nodes that share an element.
%
%    Therefore, we can compute the bandwidth by examining each element,
%    and finding the maximum difference in indices of any two variables
%    associated with nodes in that element.
%
%  Modified:
%
%    30 July 2005
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, integer ELEMENT_NUM, the number of elements.
%
%    Input, integer ELEMENT_NODE(6,ELEMENT_NUM);
%    ELEMENT_NODE(I,J) is the global index of local node I in element J.
%
%    Input, integer NODE_NUM, the number of nodes.
%
%    Input, integer NODE_P_VARIABLE(NODE_NUM),
%    is the index of the pressure variable associated with the node,
%    or -1 if there is no associated pressure variable.
%
%    Input, integer NODE_U_VARIABLE(NODE_NUM),
%    is the index of the horizontal velocity variable associated with the node.
%
%    Input, integer NODE_V_VARIABLE(NODE_NUM),
%    is the index of the vertical velocity variable associated with the node.
%
%    Output, integer IB, the half bandwidth of the matrix.
%
  ib = 0;

  for element = 1 : element_num

    v_max = -i4_huge ( 'DUMMY' );
    v_min = i4_huge ( 'DUMMY' );

    for local = 1 : 6

      node = element_node(local,element);

      v = node_u_variable(node);
      v_max = max ( v_max, v );
      v_min = min ( v_min, v );

      v = node_v_variable(node);
      v_max = max ( v_max, v );
      v_min = min ( v_min, v );

      if ( 0 < node_p_variable(node) )
        v = node_p_variable(node);
        v_max = max ( v_max, v );
        v_min = min ( v_min, v );
      end

    end

    ib = max ( ib, v_max - v_min );

  end