maxflow_ff.cpp

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/* This software is distributed under the GNU Lesser General Public License */
//==========================================================================
//
//   maxflow_ff.cpp 
//
//==========================================================================
// $Id: maxflow_ff.cpp,v 1.7 2001/11/07 13:58:10 pick Exp $

#include <GTL/maxflow_ff.h>

#include <cstdlib>
#include <iostream>
#include <cassert>

#ifdef __GTL_MSVCC
#   ifdef _DEBUG
#       ifndef SEARCH_MEMORY_LEAKS_ENABLED
#       error SEARCH NOT ENABLED
#       endif
#       define new DEBUG_NEW
#       undef THIS_FILE
        static char THIS_FILE[] = __FILE__;
#   endif   // _DEBUG
#endif  // __GTL_MSVCC

__GTL_BEGIN_NAMESPACE

maxflow_ff::maxflow_ff()
{
    max_graph_flow = 0.0;
    set_vars_executed = false;
}


maxflow_ff::~maxflow_ff()
{
}


void maxflow_ff::set_vars(const edge_map<double>& edge_capacity)
{
    this->edge_capacity = edge_capacity;
    artif_source_target = true;
    max_graph_flow = 0.0;
    set_vars_executed = true;
}


void maxflow_ff::set_vars(const edge_map<double>& edge_capacity, 
    const node& net_source, const node& net_target)
{
    this->edge_capacity = edge_capacity;
    this->net_source = net_source;
    this->net_target = net_target;
    artif_source_target = false;
    max_graph_flow = 0.0;
    set_vars_executed = true;
}


int maxflow_ff::check(graph& G)
{
    if (!set_vars_executed)
    {
        return(GTL_ERROR);
    }
    graph::edge_iterator edge_it = G.edges_begin();
    graph::edge_iterator edges_end = G.edges_end();
    while (edge_it != edges_end)
    {
        if (edge_capacity[*edge_it] < 0)
        {
            return(GTL_ERROR);
        }
        ++edge_it;
    }
    // G.is_acyclic may be false
    if ((G.number_of_nodes() <= 1) || (!G.is_connected()) || (G.is_undirected()))
    {
        return(GTL_ERROR);
    }
    if (artif_source_target)
    {
        bool source_found = false;
        bool target_found = false;
        graph::node_iterator node_it = G.nodes_begin();
        graph::node_iterator nodes_end = G.nodes_end();
        while (node_it != nodes_end)
        {
            if ((*node_it).indeg() == 0)
            {
                source_found = true;
            }
            if ((*node_it).outdeg() == 0)
            {
                target_found = true;
            }
            ++node_it;
        }
        if (!(source_found && target_found))
        {
            return(GTL_ERROR);
        }
    }
    else
    {
        if (net_source == net_target)
        {
            return(GTL_ERROR);
        }
    }
    return(GTL_OK);     // ok
}


int maxflow_ff::run(graph& G)
{
    // init
    if (artif_source_target)
    {
        create_artif_source_target(G);
    }
    prepare_run(G);

    node_map<edge> last_edge(G);

    while (get_sp(G, last_edge) == SP_FOUND)
    {
        comp_single_flow(G, last_edge);
    }

    restore_graph(G);
    return(GTL_OK);
}


double maxflow_ff::get_max_flow(const edge& e) const
{
    return(edge_max_flow[e]);
}


double maxflow_ff::get_max_flow() const
{
    return(max_graph_flow);
}


double maxflow_ff::get_rem_cap(const edge& e) const
{
    return(edge_capacity[e] - edge_max_flow[e]);
}


void maxflow_ff::reset()
{
}


void maxflow_ff::create_artif_source_target(graph& G)
{
    net_source = G.new_node();
    net_target = G.new_node();
    edge e;
    graph::node_iterator node_it = G.nodes_begin();
    graph::node_iterator nodes_end = G.nodes_end();
    while (node_it != nodes_end)
    {
        if (*node_it != net_source && (*node_it).indeg() == 0)
        {
            e = G.new_edge(net_source, *node_it);
            edge_capacity[e] = 1.0;     // 1.0 prevents e from hiding
            node::out_edges_iterator out_edge_it = (*node_it).out_edges_begin();
            node::out_edges_iterator out_edges_end = (*node_it).out_edges_end();
            while (out_edge_it != out_edges_end)
            {
                edge_capacity[e] += edge_capacity[*out_edge_it];
                ++out_edge_it;
            }
        }
        if (*node_it != net_target && (*node_it).outdeg() == 0)
        {
            e = G.new_edge(*node_it, net_target);
            edge_capacity[e] = 1.0;     // 1.0 prevents e from hiding
            node::in_edges_iterator in_edge_it = (*node_it).in_edges_begin();
            node::in_edges_iterator in_edges_end = (*node_it).in_edges_end();
            while (in_edge_it != in_edges_end)
            {
                edge_capacity[e] += edge_capacity[*in_edge_it];
                ++in_edge_it;
            }
        }
        ++node_it;
    }
}


void maxflow_ff::prepare_run(const graph& G)
{
    edge_max_flow.init(G, 0.0);
    edge_org.init(G, true);
    back_edge_exists.init(G, false);
    max_graph_flow = 0.0;
}


void maxflow_ff::comp_single_flow(graph& G, node_map<edge>& last_edge)
{
    double min_value = extra_charge(last_edge);

    node cur_node = net_target;
    do
    {
        if (edge_org[last_edge[cur_node]])      // shortest path runs over a org. edge
        {
            if (!back_edge_exists[last_edge[cur_node]]) // create back edge
            {
                create_back_edge(G, last_edge[cur_node]);
            }
            edge_max_flow[last_edge[cur_node]] += min_value;
            G.restore_edge(back_edge[last_edge[cur_node]]);
            edge_capacity[back_edge[last_edge[cur_node]]] += min_value;
        }
        else    // shortest path runs over a inserted back edge
        {
            edge oe = back_edge[last_edge[cur_node]];
            G.restore_edge(oe);
            edge_max_flow[oe] -= min_value;
            edge_capacity[last_edge[cur_node]] -= min_value;
        }
        if (edge_capacity[last_edge[cur_node]] <= edge_max_flow[last_edge[cur_node]])
        {
            G.hide_edge(last_edge[cur_node]);
        }
        cur_node = last_edge[cur_node].source();
    }
    while (cur_node != net_source);
}


int maxflow_ff::get_sp(const graph& G, node_map<edge>& last_edge)
{
    queue<node> next_nodes;
    node_map<bool> visited(G, false);
    next_nodes.push(net_source);
    visited[net_source] = true;

    if (comp_sp(G, next_nodes, visited, last_edge) == SP_FOUND)
    {
        return(SP_FOUND);
    }
    else
    {
        return(NO_SP_FOUND);
    }
}


int maxflow_ff::comp_sp(const graph& G, queue<node>& next_nodes, 
    node_map<bool>& visited, node_map<edge>& last_edge)
{
    node cur_node;

    while (!next_nodes.empty())
    {
        cur_node = next_nodes.front();
        next_nodes.pop();
                
        node::out_edges_iterator out_edge_it = cur_node.out_edges_begin();
        node::out_edges_iterator out_edges_end = cur_node.out_edges_end();
        while (out_edge_it != out_edges_end)
        {
            node next = (*out_edge_it).target();
            if (!visited[next])
            {
                last_edge[next] = *out_edge_it;
                if (next == net_target)
                {
                    return(SP_FOUND);
                }
                else
                {
                    next_nodes.push(next);
                    visited[next] = true;
                }
            }
            ++out_edge_it;
        }
    }
    return(NO_SP_FOUND);
}


double maxflow_ff::extra_charge(const node_map<edge>& last_edge) const
{
    node cur_node = net_target;
    double min_value = 
        edge_capacity[last_edge[cur_node]] - edge_max_flow[last_edge[cur_node]];
    double cur_capacity;

    do
    {
        cur_capacity = 
            edge_capacity[last_edge[cur_node]] - edge_max_flow[last_edge[cur_node]];

        if (cur_capacity < min_value) min_value = cur_capacity;
        cur_node = last_edge[cur_node].source();
    }
    while (cur_node != net_source);
    return(min_value);
}


void maxflow_ff::create_back_edge(graph& G, const edge& org_edge)
{
    edge be = G.new_edge(org_edge.target(), org_edge.source());
    edge_org[be] = false;
    edges_not_org.push_back(be);
    back_edge[org_edge] = be;
    back_edge[be] = org_edge;
    edge_max_flow[be] = 0.0;
    edge_capacity[be] = 0.0;
    back_edge_exists[org_edge] = true;
    back_edge_exists[be] = true;        // a back edge always has a org. edge ;-)
}


void maxflow_ff::comp_max_flow(const graph& G)
{
    max_graph_flow = 0.0;

    node::out_edges_iterator out_edge_it = net_source.out_edges_begin();
    node::out_edges_iterator out_edges_end = net_source.out_edges_end();
    while (out_edge_it != out_edges_end)
    {
        max_graph_flow += edge_max_flow[*out_edge_it];
        ++out_edge_it;
    }
}


void maxflow_ff::restore_graph(graph& G)
{
    G.restore_graph();  // hidden edges can not be deleted!
    while (!edges_not_org.empty())
    {
        G.del_edge(edges_not_org.front());
        edges_not_org.pop_front();
    }
    comp_max_flow(G);
    if (artif_source_target)
    {
        G.del_node(net_source);
        G.del_node(net_target);
    }
}

__GTL_END_NAMESPACE

//--------------------------------------------------------------------------
//   end of file
//--------------------------------------------------------------------------