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| <Head> |
| <Title>Boost Graph Library: Successive Shortest Path for Min Cost Max Flow</Title> |
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| <H1><A NAME="sec:successive_shortest_path_nonnegative_weights"> |
| <TT>successive_shortest_path_nonnegative_weights</TT> |
| </H1> |
| |
| <PRE> |
| <i>// named parameter version</i> |
| template <class <a href="./Graph.html">Graph</a>, class P, class T, class R> |
| void successive_shortest_path_nonnegative_weights( |
| Graph &g, |
| typename graph_traits<Graph>::vertex_descriptor s, |
| typename graph_traits<Graph>::vertex_descriptor t, |
| const bgl_named_params<P, T, R> & params = <i>all defaults</i>) |
| |
| <i>// non-named parameter version</i> |
| template <class <a href="./Graph.html">Graph</a>, class Capacity, class ResidualCapacity, class Reversed, class Pred, class Weight, class Distance, class Distance2, class VertexIndex> |
| void successive_shortest_path_nonnegative_weights( |
| const Graph & g, |
| typename graph_traits<Graph>::vertex_descriptor s, |
| typename graph_traits<Graph>::vertex_descriptor t, |
| Capacity capacity, |
| ResidualCapacity residual_capacity, |
| Weight weight, |
| Reversed rev, |
| VertexIndex index, |
| Pred pred, |
| Distance distance, |
| Distance2 distance_prev) |
| </PRE> |
| |
| <P> |
| The <tt>successive_shortest_path_nonnegative_weights()</tt> function calculates the minimum cost maximum flow of a network. See Section <a |
| href="./graph_theory_review.html#sec:network-flow-algorithms">Network |
| Flow Algorithms</a> for a description of maximum flow. |
| The function calculates the flow values <i>f(u,v)</i> for all <i>(u,v)</i> in |
| <i>E</i>, which are returned in the form of the residual capacity |
| <i>r(u,v) = c(u,v) - f(u,v)</i>. |
| |
| <p> |
| There are several special requirements on the input graph and property |
| map parameters for this algorithm. First, the directed graph |
| <i>G=(V,E)</i> that represents the network must be augmented to |
| include the reverse edge for every edge in <i>E</i>. That is, the |
| input graph should be <i>G<sub>in</sub> = (V,{E U |
| E<sup>T</sup>})</i>. The <tt>ReverseEdgeMap</tt> argument <tt>rev</tt> |
| must map each edge in the original graph to its reverse edge, that is |
| <i>(u,v) -> (v,u)</i> for all <i>(u,v)</i> in <i>E</i>. The |
| <tt>CapacityEdgeMap</tt> argument <tt>cap</tt> must map each edge in |
| <i>E</i> to a positive number, and each edge in <i>E<sup>T</sup></i> |
| to 0. The <tt>WeightMap</tt> has to map each edge from <i>E</i> to nonnegative number, and each edge from <i>E<sup>T</sup></i> to <i>-weight</i> of its reversed edge. |
| |
| <p> |
| The algorithm is described in <a |
| href="./bibliography.html#ahuja93:_network_flows">Network Flows</a>. |
| |
| <p> |
| This algorithm starts with empty flow and in each round augments the shortest path (in terms of weight) in the residual graph. |
| |
| <p> |
| In order to find the cost of the result flow use: |
| <a href="./find_flow_cost.html"><tt>find_flow_cost()</tt></a>. |
| |
| <H3>Where Defined</H3> |
| |
| <P> |
| <a href="../../../boost/graph/successive_shortest_path_nonnegative_weights.hpp"><TT>boost/graph/successive_shortest_path_nonnegative_weights.hpp</TT></a> |
| |
| <P> |
| |
| <h3>Parameters</h3> |
| |
| IN: <tt>Graph& g</tt> |
| <blockquote> |
| A directed graph. The |
| graph's type must be a model of <a |
| href="./VertexListGraph.html">VertexListGraph</a> and <a href="./IncidenceGraph.html">IncidenceGraph</a> For each edge |
| <i>(u,v)</i> in the graph, the reverse edge <i>(v,u)</i> must also |
| be in the graph. |
| </blockquote> |
| |
| IN: <tt>vertex_descriptor s</tt> |
| <blockquote> |
| The source vertex for the flow network graph. |
| </blockquote> |
| |
| IN: <tt>vertex_descriptor t</tt> |
| <blockquote> |
| The sink vertex for the flow network graph. |
| </blockquote> |
| |
| <h3>Named Parameters</h3> |
| |
| |
| IN: <tt>capacity_map(CapacityEdgeMap cap)</tt> |
| <blockquote> |
| The edge capacity property map. The type must be a model of a |
| constant <a |
| href="../../property_map/doc/LvaluePropertyMap.html">Lvalue Property Map</a>. The |
| key type of the map must be the graph's edge descriptor type.<br> |
| <b>Default:</b> <tt>get(edge_capacity, g)</tt> |
| </blockquote> |
| |
| OUT: <tt>residual_capacity_map(ResidualCapacityEdgeMap res)</tt> |
| <blockquote> |
| This maps edges to their residual capacity. The type must be a model |
| of a mutable <a |
| href="../../property_map/doc/LvaluePropertyMap.html">Lvalue Property |
| Map</a>. The key type of the map must be the graph's edge descriptor |
| type.<br> |
| <b>Default:</b> <tt>get(edge_residual_capacity, g)</tt> |
| </blockquote> |
| |
| IN: <tt>reverse_edge_map(ReverseEdgeMap rev)</tt> |
| <blockquote> |
| An edge property map that maps every edge <i>(u,v)</i> in the graph |
| to the reverse edge <i>(v,u)</i>. The map must be a model of |
| constant <a href="../../property_map/doc/LvaluePropertyMap.html">Lvalue |
| Property Map</a>. The key type of the map must be the graph's edge |
| descriptor type.<br> |
| <b>Default:</b> <tt>get(edge_reverse, g)</tt> |
| </blockquote> |
| |
| IN: <tt>weight_map(WeightMap w_map)</tt> |
| <blockquote> |
| The weight or ``cost'' of each edge in the graph. The weights |
| must all be non-negative, and the algorithm will throw a |
| <a href="./exception.html#negative_edge"><tt>negative_edge</tt></a> |
| exception if one of the edges is negative. |
| The type <tt>WeightMap</tt> must be a model of |
| <a href="../../property_map/doc/ReadablePropertyMap.html">Readable Property Map</a>. The edge descriptor type of |
| the graph needs to be usable as the key type for the weight |
| map. The value type for this map must be |
| the same as the value type of the distance map.<br> |
| <b>Default:</b> <tt>get(edge_weight, g)</tt><br> |
| |
| </blockquote> |
| |
| UTIL: <tt>predecessor_map(PredEdgeMap pred)</tt> |
| <blockquote> |
| Use by the algorithm to store augmenting paths. The map must be a |
| model of mutable <a |
| href="../../property_map/doc/LvaluePropertyMap.html">Lvalue Property Map</a>. |
| The key type must be the graph's vertex descriptor type and the |
| value type must be the graph's edge descriptor type.<br> |
| |
| <b>Default:</b> an <a |
| href="../../property_map/doc/iterator_property_map.html"> |
| <tt>iterator_property_map</tt></a> created from a <tt>std::vector</tt> |
| of edge descriptors of size <tt>num_vertices(g)</tt> and |
| using the <tt>i_map</tt> for the index map. |
| </blockquote> |
| |
| UTIL: <tt>distance_map(DistanceMap d_map)</tt> |
| <blockquote> |
| The shortest path weight from the source vertex <tt>s</tt> to each |
| vertex in the graph <tt>g</tt> is recorded in this property map. The |
| shortest path weight is the sum of the edge weights along the |
| shortest path. The type <tt>DistanceMap</tt> must be a model of <a |
| href="../../property_map/doc/ReadWritePropertyMap.html">Read/Write |
| Property Map</a>. The vertex descriptor type of the graph needs to |
| be usable as the key type of the distance map. |
| |
| <b>Default:</b> <a |
| href="../../property_map/doc/iterator_property_map.html"> |
| <tt>iterator_property_map</tt></a> created from a |
| <tt>std::vector</tt> of the <tt>WeightMap</tt>'s value type of size |
| <tt>num_vertices(g)</tt> and using the <tt>i_map</tt> for the index |
| map.<br> |
| |
| </blockquote> |
| |
| UTIL: <tt>distance_map2(DistanceMap2 d_map2)</tt> |
| <blockquote> |
| The shortest path computation in iteration nr <i>k</i> uses distances computed in iteration <i>k</i>. |
| The type <tt>DistanceMap2</tt> must be a model of <a |
| href="../../property_map/doc/ReadWritePropertyMap.html">Read/Write |
| Property Map</a>. The vertex descriptor type of the graph needs to |
| be usable as the key type of the distance map. |
| |
| <b>Default:</b> <a |
| href="../../property_map/doc/iterator_property_map.html"> |
| <tt>iterator_property_map</tt></a> created from a |
| <tt>std::vector</tt> of the <tt>WeightMap</tt>'s value type of size |
| <tt>num_vertices(g)</tt> and using the <tt>i_map</tt> for the index |
| map.<br> |
| |
| </blockquote> |
| |
| IN: <tt>vertex_index_map(VertexIndexMap i_map)</tt> |
| <blockquote> |
| Maps each vertex of the graph to a unique integer in the range |
| <tt>[0, num_vertices(g))</tt>. This property map is only needed |
| if the default for the distance or distance2 or predecessor map is used. |
| The vertex index map must be a model of <a |
| href="../../property_map/doc/ReadablePropertyMap.html">Readable Property |
| Map</a>. The key type of the map must be the graph's vertex |
| descriptor type.<br> |
| <b>Default:</b> <tt>get(vertex_index, g)</tt> |
| Note: if you use this default, make sure your graph has |
| an internal <tt>vertex_index</tt> property. For example, |
| <tt>adjacenty_list</tt> with <tt>VertexList=listS</tt> does |
| not have an internal <tt>vertex_index</tt> property. |
| </blockquote> |
| |
| |
| <h3>Complexity</h3> |
| In the integer capacity case, if <i>U</i> is the value of the max flow, then the complexity is <i> O(U * (|E| + |V|*log|V|))</i>, |
| where <i>O(|E| + |V|*log|V|)</i> is the complexity of the dijkstra algorithm and <i>U</i> is upper bound on number of iteration. |
| In many real world cases number of iterations is much smaller than <i>U</i>. |
| |
| |
| <h3>Example</h3> |
| |
| The program in <a |
| href="../example/successive_shortest_path_nonnegative_weights_example.cpp"><tt>example/successive_shortest_path_nonnegative_weights_example.cpp</tt></a>. |
| |
| <h3>See Also</h3> |
| |
| <a href="./cycle_canceling.html"><tt>cycle_canceling()</tt></a><br> |
| <a href="./find_flow_cost.html"><tt>find_flow_cost()</tt></a>. |
| |
| <br> |
| <HR> |
| <TABLE> |
| <TR valign=top> |
| <TD nowrap>Copyright © 2013</TD><TD> |
| Piotr Wygocki, University of Warsaw (<A HREF="mailto:wygos@mimuw.edu.pl">wygos at mimuw.edu.pl</A>) |
| </TD></TR></TABLE> |
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