2 @defgroup gwrappers Wrapper Classes for Graphs
3 \brief This group contains several wrapper classes for graphs
6 The main parts of LEMON are the different graph structures,
7 generic graph algorithms, graph concepts which couple these, and
8 graph wrappers. While the previous ones are more or less clear, the
9 latter notion needs further explanation.
10 Graph wrappers are graph classes which serve for considering graph
11 structures in different ways. A short example makes the notion much
13 Suppose that we have an instance \c g of a directed graph
14 type say \c ListGraph and an algorithm
15 \code template<typename Graph> int algorithm(const Graph&); \endcode
16 is needed to run on the reversely oriented graph.
17 It may be expensive (in time or in memory usage) to copy
18 \c g with the reverse orientation.
20 \code template<typename Graph> class RevGraphWrapper; \endcode is used.
21 The code looks as follows
24 RevGraphWrapper<ListGraph> rgw(g);
25 int result=algorithm(rgw);
27 After running the algorithm, the original graph \c g
28 remains untouched. Thus the graph wrapper used above is to consider the
29 original graph with reverse orientation.
30 This techniques gives rise to an elegant code, and
31 based on stable graph wrappers, complex algorithms can be
33 In flow, circulation and bipartite matching problems, the residual
34 graph is of particular importance. Combining a wrapper implementing
35 this, shortest path algorithms and minimum mean cycle algorithms,
36 a range of weighted and cardinality optimization algorithms can be
37 obtained. For lack of space, for other examples,
38 the interested user is referred to the detailed documentation of graph
40 The behavior of graph wrappers can be very different. Some of them keep
41 capabilities of the original graph while in other cases this would be
42 meaningless. This means that the concepts that they are a model of depend
43 on the graph wrapper, and the wrapped graph(s).
44 If an edge of \c rgw is deleted, this is carried out by
45 deleting the corresponding edge of \c g. But for a residual
46 graph, this operation has no sense.
47 Let we stand one more example here to simplify your work.
49 \code template<typename Graph> class RevGraphWrapper; \endcode
51 <tt> RevGraphWrapper(Graph& _g)</tt>.
52 This means that in a situation,
53 when a <tt> const ListGraph& </tt> reference to a graph is given,
54 then it have to be instantiated with <tt>Graph=const ListGraph</tt>.
56 int algorithm1(const ListGraph& g) {
57 RevGraphWrapper<const ListGraph> rgw(g);
58 return algorithm2(rgw);