TrustGraph.h

//------------------------------------------------------------------------------
/*
    This file is part of rippled: https://github.com/ripple/rippled
    Copyright (c) 2012-2017 Ripple Labs Inc
 
    Permission to use, copy, modify, and/or distribute this software for any
    purpose  with  or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.
 
    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================
 
#ifndef RIPPLE_TEST_CSF_UNL_H_INCLUDED
#define RIPPLE_TEST_CSF_UNL_H_INCLUDED
 
#include <test/csf/random.h>
#include <boost/container/flat_set.hpp>
 
#include <chrono>
#include <numeric>
#include <random>
#include <vector>
 
namespace ripple {
namespace test {
namespace csf {
 
template <class Peer>
class TrustGraph
{
    using Graph = Digraph<Peer>;
 
    Graph graph_;
 
public:
    TrustGraph() = default;
 
    Graph const&
    graph()
    {
        return graph_;
    }
 
    void
    trust(Peer const& from, Peer const& to)
    {
        graph_.connect(from, to);
    }
 
    void
    untrust(Peer const& from, Peer const& to)
    {
        graph_.disconnect(from, to);
    }
 
    //< Whether from trusts to
    bool
    trusts(Peer const& from, Peer const& to) const
    {
        return graph_.connected(from, to);
    }
 
    auto
    trustedPeers(Peer const& a) const
    {
        return graph_.outVertices(a);
    }
 
    struct ForkInfo
    {
        std::set<Peer> unlA;
        std::set<Peer> unlB;
        int overlap;
        double required;
    };
 
    //< Return nodes that fail the white-paper no-forking condition
    std::vector<ForkInfo>
    forkablePairs(double quorum) const
    {
        // Check the forking condition by looking at intersection
        // of UNL between all pairs of nodes.
 
        // TODO: Use the improved bound instead of the whitepaper bound.
 
        using UNL = std::set<Peer>;
        std::set<UNL> unique;
        for (Peer const peer : graph_.outVertices())
        {
            unique.emplace(
                std::begin(trustedPeers(peer)), std::end(trustedPeers(peer)));
        }
 
        std::vector<UNL> uniqueUNLs(unique.begin(), unique.end());
        std::vector<ForkInfo> res;
 
        // Loop over all pairs of uniqueUNLs
        for (int i = 0; i < uniqueUNLs.size(); ++i)
        {
            for (int j = (i + 1); j < uniqueUNLs.size(); ++j)
            {
                auto const& unlA = uniqueUNLs[i];
                auto const& unlB = uniqueUNLs[j];
                double rhs =
                    2.0 * (1. - quorum) * std::max(unlA.size(), unlB.size());
 
                int intersectionSize =
                    std::count_if(unlA.begin(), unlA.end(), [&](Peer p) {
                        return unlB.find(p) != unlB.end();
                    });
 
                if (intersectionSize < rhs)
                {
                    res.emplace_back(
                        ForkInfo{unlA, unlB, intersectionSize, rhs});
                }
            }
        }
        return res;
    }
 
    bool
    canFork(double quorum) const
    {
        return !forkablePairs(quorum).empty();
    }
};
 
}  // namespace csf
}  // namespace test
}  // namespace ripple
 
#endif