graph_eigenvector.hh 4.08 KB
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// graph-tool -- a general graph modification and manipulation thingy
//
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// Copyright (C) 2006-2015 Tiago de Paula Peixoto <tiago@skewed.de>
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//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 3
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.

#ifndef GRAPH_EIGENVECTOR_HH
#define GRAPH_EIGENVECTOR_HH

#include "graph.hh"
#include "graph_filtering.hh"
#include "graph_util.hh"

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#ifndef __clang__
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#include <ext/numeric>
using __gnu_cxx::power;
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#else
template <class Value>
Value power(Value value, int n)
{
    return pow(value, n);
}
#endif
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namespace graph_tool
{
using namespace std;
using namespace boost;

struct get_eigenvector
{
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    template <class Graph, class VertexIndex, class WeightMap,
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              class CentralityMap>
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    void operator()(Graph& g, VertexIndex vertex_index, WeightMap w,
                    CentralityMap c, double epsilon, size_t max_iter,
                    long double& eig) const
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    {
        typedef typename property_traits<WeightMap>::value_type c_type;
        typedef typename property_traits<CentralityMap>::value_type t_type;

        CentralityMap c_temp(vertex_index, num_vertices(g));

        t_type norm = 0;
        t_type delta = epsilon + 1;
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        t_type prev_delta = delta + 1;
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        size_t iter = 0;
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        int i, N = num_vertices(g);
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        while (delta >= epsilon)
        {
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            prev_delta = delta;
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            norm = 0;
            #pragma omp parallel for default(shared) private(i) \
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                schedule(runtime) if (N > 100) reduction(+:norm)
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            for (i = 0; i < N; ++i)
            {
                typename graph_traits<Graph>::vertex_descriptor v =
                    vertex(i, g);
                if (v == graph_traits<Graph>::null_vertex())
                    continue;

                c_temp[v] = 0;
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                typename in_or_out_edge_iteratorS<Graph>::type e, e_end;
                for (tie(e, e_end) = in_or_out_edge_iteratorS<Graph>::get_edges(v, g);
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                     e != e_end; ++e)
                {
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                    typename graph_traits<Graph>::vertex_descriptor s;
                    if (is_directed::apply<Graph>::type::value)
                        s = source(*e,g);
                    else
                        s = target(*e,g);
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                    c_temp[v] += get(w, *e) * c[s];
                }
                norm += power(c_temp[v], 2);
            }
            norm = sqrt(norm);

            delta = 0;
            #pragma omp parallel for default(shared) private(i) \
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                schedule(runtime) if (N > 100) reduction(+:delta)
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            for (i = 0; i < N; ++i)
            {
                typename graph_traits<Graph>::vertex_descriptor v =
                    vertex(i, g);
                if (v == graph_traits<Graph>::null_vertex())
                    continue;
                c_temp[v] /= norm;
                delta += abs(c_temp[v] - c[v]);
            }
            swap(c_temp, c);

            ++iter;
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            if (max_iter > 0 && iter == max_iter)
                break;
            if (max_iter == 0 && delta > prev_delta && iter > 100)
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                break;
        }

        if (iter % 2 != 0)
        {
            #pragma omp parallel for default(shared) private(i)     \
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                schedule(runtime) if (N > 100)
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            for (i = 0; i < N; ++i)
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            {
                typename graph_traits<Graph>::vertex_descriptor v =
                    vertex(i, g);
                if (v == graph_traits<Graph>::null_vertex())
                    continue;
                c[v] = c_temp[v];
            }
        }
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        eig = norm;
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    }
};

}

#endif