Grid/extras/Hadrons/Graph.hpp

/*************************************************************************************

Grid physics library, www.github.com/paboyle/Grid 

Source file: extras/Hadrons/Graph.hpp

Copyright (C) 2015-2018

Author: Antonin Portelli <antonin.portelli@me.com>

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 2 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, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

See the full license in the file "LICENSE" in the top level distribution directory
*************************************************************************************/
/*  END LEGAL */

#ifndef Hadrons_Graph_hpp_
#define Hadrons_Graph_hpp_

#include <Grid/Hadrons/Global.hpp>

BEGIN_HADRONS_NAMESPACE

/******************************************************************************
 *                          Oriented graph class                              *
 ******************************************************************************/
// I/O for edges
template <typename T>
std::ostream & operator<<(std::ostream &out, const std::pair<T, T> &e)
{
    out << "\""  << e.first << "\" -> \"" << e.second << "\"";
    
    return out;
}

// main class
template <typename T>
class Graph
{
public:
    typedef std::pair<T, T> Edge;
public:
    // constructor
    Graph(void);
    // destructor
    virtual ~Graph(void) = default;
    // access
    void           addVertex(const T &value);
    void           addEdge(const Edge &e);
    void           addEdge(const T &start, const T &end);
    std::vector<T> getVertices(void) const;
    void           removeVertex(const T &value);
    void           removeEdge(const Edge &e);
    void           removeEdge(const T &start, const T &end);
    unsigned int   size(void) const;
    // tests
    bool gotValue(const T &value) const;
    // graph topological manipulations
    std::vector<T>              getAdjacentVertices(const T &value) const;
    std::vector<T>              getChildren(const T &value) const;
    std::vector<T>              getParents(const T &value) const;
    std::vector<T>              getRoots(void) const;
    std::vector<Graph<T>>       getConnectedComponents(void) const;
    std::vector<T>              topoSort(void);
    template <typename Gen>
    std::vector<T>              topoSort(Gen &gen);
    std::vector<std::vector<T>> allTopoSort(void);
    // I/O
    friend std::ostream & operator<<(std::ostream &out, const Graph<T> &g)
    {
        out << "{";
        for (auto &e: g.edgeSet_)
        {
            out << e << ", ";
        }
        if (g.edgeSet_.size() != 0)
        {
            out << "\b\b";
        }
        out << "}";
        
        return out;
    }
private:
    // vertex marking
    void      mark(const T &value, const bool doMark = true);
    void      markAll(const bool doMark = true);
    void      unmark(const T &value);
    void      unmarkAll(void);
    bool      isMarked(const T &value) const;
    const T * getFirstMarked(const bool isMarked = true) const;
    template <typename Gen>
    const T * getRandomMarked(const bool isMarked, Gen &gen);
    const T * getFirstUnmarked(void) const;
    template <typename Gen>
    const T * getRandomUnmarked(Gen &gen);
    // prune marked/unmarked vertices
    void removeMarked(const bool isMarked = true);
    void removeUnmarked(void);
    // depth-first search marking
    void depthFirstSearch(void);
    void depthFirstSearch(const T &root);
private:
    std::map<T, bool>  isMarked_;
    std::set<Edge>     edgeSet_;
};

// build depedency matrix from topological sorts
template <typename T>
std::map<T, std::map<T, bool>>
makeDependencyMatrix(const std::vector<std::vector<T>> &topSort);

/******************************************************************************
 *                       template implementation                              *
 ******************************************************************************
 * in all the following V is the number of vertex and E is the number of edge
 * in the worst case E = V^2
 */

// constructor /////////////////////////////////////////////////////////////////
template <typename T>
Graph<T>::Graph(void)
{}

// access //////////////////////////////////////////////////////////////////////
// complexity: log(V)
template <typename T>
void Graph<T>::addVertex(const T &value)
{
    isMarked_[value] = false;
}

// complexity: O(log(V))
template <typename T>
void Graph<T>::addEdge(const Edge &e)
{
    addVertex(e.first);
    addVertex(e.second);
    edgeSet_.insert(e);
}

// complexity: O(log(V))
template <typename T>
void Graph<T>::addEdge(const T &start, const T &end)
{
    addEdge(Edge(start, end));
}

template <typename T>
std::vector<T> Graph<T>::getVertices(void) const
{
    std::vector<T> vertex;
    
    for (auto &v: isMarked_)
    {
        vertex.push_back(v.first);
    }
    
    return vertex;
}

// complexity: O(V*log(V))
template <typename T>
void Graph<T>::removeVertex(const T &value)
{
    // remove vertex from the mark table
    auto vIt = isMarked_.find(value);
    
    if (vIt != isMarked_.end())
    {
        isMarked_.erase(vIt);
    }
    else
    {
        HADRON_ERROR(Range, "vertex does not exists");
    }

    // remove all edges containing the vertex
    auto pred = [&value](const Edge &e)
    {
        return ((e.first == value) or (e.second == value));
    };
    auto eIt = find_if(edgeSet_.begin(), edgeSet_.end(), pred);
    
    while (eIt != edgeSet_.end())
    {
        edgeSet_.erase(eIt);
        eIt = find_if(edgeSet_.begin(), edgeSet_.end(), pred);
    }
}

// complexity: O(log(V))
template <typename T>
void Graph<T>::removeEdge(const Edge &e)
{
    auto eIt = edgeSet_.find(e);
    
    if (eIt != edgeSet_.end())
    {
        edgeSet_.erase(eIt);
    }
    else
    {
        HADRON_ERROR(Range, "edge does not exists");
    }
}

// complexity: O(log(V))
template <typename T>
void Graph<T>::removeEdge(const T &start, const T &end)
{
    removeEdge(Edge(start, end));
}

// complexity: O(1)
template <typename T>
unsigned int Graph<T>::size(void) const
{
    return isMarked_.size();
}

// tests ///////////////////////////////////////////////////////////////////////
// complexity: O(log(V))
template <typename T>
bool Graph<T>::gotValue(const T &value) const
{
    auto it = isMarked_.find(value);
    
    if (it == isMarked_.end())
    {
        return false;
    }
    else
    {
        return true;
    }
}

// vertex marking //////////////////////////////////////////////////////////////
// complexity: O(log(V))
template <typename T>
void Graph<T>::mark(const T &value, const bool doMark)
{
    if (gotValue(value))
    {
        isMarked_[value] = doMark;
    }
    else
    {
        HADRON_ERROR(Range, "vertex does not exists");
    }
}

// complexity: O(V*log(V))
template <typename T>
void Graph<T>::markAll(const bool doMark)
{
    for (auto &v: isMarked_)
    {
        mark(v.first, doMark);
    }
}

// complexity: O(log(V))
template <typename T>
void Graph<T>::unmark(const T &value)
{
    mark(value, false);
}

// complexity: O(V*log(V))
template <typename T>
void Graph<T>::unmarkAll(void)
{
    markAll(false);
}

// complexity: O(log(V))
template <typename T>
bool Graph<T>::isMarked(const T &value) const
{
    if (gotValue(value))
    {
        return isMarked_.at(value);
    }
    else
    {
        HADRON_ERROR(Range, "vertex does not exists");
        
        return false;
    }
}

// complexity: O(log(V))
template <typename T>
const T * Graph<T>::getFirstMarked(const bool isMarked) const
{
    auto pred = [&isMarked](const std::pair<T, bool> &v)
    {
        return (v.second == isMarked);
    };
    auto vIt = std::find_if(isMarked_.begin(), isMarked_.end(), pred);
    
    if (vIt != isMarked_.end())
    {
        return &(vIt->first);
    }
    else
    {
        return nullptr;
    }
}

// complexity: O(log(V))
template <typename T>
template <typename Gen>
const T * Graph<T>::getRandomMarked(const bool isMarked, Gen &gen)
{
    auto pred = [&isMarked](const std::pair<T, bool> &v)
    {
        return (v.second == isMarked);
    };
    std::uniform_int_distribution<unsigned int> dis(0, size() - 1);
    auto                                        rIt = isMarked_.begin();
    
    std::advance(rIt, dis(gen));
    auto vIt = std::find_if(rIt, isMarked_.end(), pred);
    if (vIt != isMarked_.end())
    {
        return &(vIt->first);
    }
    else
    {
        vIt = std::find_if(isMarked_.begin(), rIt, pred);
        if (vIt != rIt)
        {
            return &(vIt->first);
        }
        else
        {
            return nullptr;
        }
    }
}

// complexity: O(log(V))
template <typename T>
const T * Graph<T>::getFirstUnmarked(void) const
{
    return getFirstMarked(false);
}

// complexity: O(log(V))
template <typename T>
template <typename Gen>
const T * Graph<T>::getRandomUnmarked(Gen &gen)
{
    return getRandomMarked(false, gen);
}

// prune marked/unmarked vertices //////////////////////////////////////////////
// complexity: O(V^2*log(V))
template <typename T>
void Graph<T>::removeMarked(const bool isMarked)
{
    auto isMarkedCopy = isMarked_;
    
    for (auto &v: isMarkedCopy)
    {
        if (v.second == isMarked)
        {
            removeVertex(v.first);
        }
    }
}

// complexity: O(V^2*log(V))
template <typename T>
void Graph<T>::removeUnmarked(void)
{
    removeMarked(false);
}

// depth-first search marking //////////////////////////////////////////////////
// complexity: O(V*log(V))
template <typename T>
void Graph<T>::depthFirstSearch(void)
{
    depthFirstSearch(isMarked_.begin()->first);
}

// complexity: O(V*log(V))
template <typename T>
void Graph<T>::depthFirstSearch(const T &root)
{
    std::vector<T> adjacentVertex;
    
    mark(root);
    adjacentVertex = getAdjacentVertices(root);
    for (auto &v: adjacentVertex)
    {
        if (!isMarked(v))
        {
            depthFirstSearch(v);
        }
    }
}

// graph topological manipulations /////////////////////////////////////////////
// complexity: O(V*log(V))
template <typename T>
std::vector<T> Graph<T>::getAdjacentVertices(const T &value) const
{
    std::vector<T> adjacentVertex;
    
    auto pred = [&value](const Edge &e)
    {
        return ((e.first == value) or (e.second == value));
    };
    auto eIt = std::find_if(edgeSet_.begin(), edgeSet_.end(), pred);
    
    while (eIt != edgeSet_.end())
    {
        if (eIt->first == value)
        {
            adjacentVertex.push_back((*eIt).second);
        }
        else if (eIt->second == value)
        {
            adjacentVertex.push_back((*eIt).first);
        }
        eIt = std::find_if(++eIt, edgeSet_.end(), pred);
    }
    
    return adjacentVertex;
}

// complexity: O(V*log(V))
template <typename T>
std::vector<T> Graph<T>::getChildren(const T &value) const
{
    std::vector<T> child;
    
    auto pred = [&value](const Edge &e)
    {
        return (e.first == value);
    };
    auto eIt = std::find_if(edgeSet_.begin(), edgeSet_.end(), pred);
    
    while (eIt != edgeSet_.end())
    {
        child.push_back((*eIt).second);
        eIt = std::find_if(++eIt, edgeSet_.end(), pred);
    }
    
    return child;
}

// complexity: O(V*log(V))
template <typename T>
std::vector<T> Graph<T>::getParents(const T &value) const
{
    std::vector<T> parent;
    
    auto pred = [&value](const Edge &e)
    {
        return (e.second == value);
    };
    auto eIt = std::find_if(edgeSet_.begin(), edgeSet_.end(), pred);
    
    while (eIt != edgeSet_.end())
    {
        parent.push_back((*eIt).first);
        eIt = std::find_if(++eIt, edgeSet_.end(), pred);
    }
    
    return parent;
}

// complexity: O(V^2*log(V))
template <typename T>
std::vector<T> Graph<T>::getRoots(void) const
{
    std::vector<T> root;
    
    for (auto &v: isMarked_)
    {
        auto parent = getParents(v.first);
        
        if (parent.size() == 0)
        {
            root.push_back(v.first);
        }
    }
    
    return root;
}

// complexity: O(V^2*log(V))
template <typename T>
std::vector<Graph<T>> Graph<T>::getConnectedComponents(void) const
{
    std::vector<Graph<T>> res;
    Graph<T>              copy(*this);
    
    while (copy.size() > 0)
    {
        copy.depthFirstSearch();
        res.push_back(copy);
        res.back().removeUnmarked();
        res.back().unmarkAll();
        copy.removeMarked();
        copy.unmarkAll();
    }
    
    return res;
}

// topological sort using a directed DFS algorithm
// complexity: O(V*log(V))
template <typename T>
std::vector<T> Graph<T>::topoSort(void)
{
    std::stack<T>     buf;
    std::vector<T>    res;
    const T           *vPt;
    std::map<T, bool> tmpMarked(isMarked_);

    // visit function
    std::function<void(const T &)> visit = [&](const T &v)
    {
        if (tmpMarked.at(v))
        {
            HADRON_ERROR(Range, "cannot topologically sort a cyclic graph");
        }
        if (!isMarked(v))
        {
            std::vector<T> child = getChildren(v);

            tmpMarked[v] = true;
            for (auto &c: child)
            {
                visit(c);
            }
            mark(v);
            tmpMarked[v] = false;
            buf.push(v);
        }
    };
    
    // reset temporary marks
    for (auto &v: tmpMarked)
    {
        tmpMarked.at(v.first) = false;
    }
    
    // loop on unmarked vertices
    unmarkAll();
    vPt = getFirstUnmarked();
    while (vPt)
    {
        visit(*vPt);
        vPt = getFirstUnmarked();
    }
    unmarkAll();
    
    // create result vector
    while (!buf.empty())
    {
        res.push_back(buf.top());
        buf.pop();
    }
    
    return res;
}

// random version of the topological sort
// complexity: O(V*log(V))
template <typename T>
template <typename Gen>
std::vector<T> Graph<T>::topoSort(Gen &gen)
{
    std::stack<T>     buf;
    std::vector<T>    res;
    const T           *vPt;
    std::map<T, bool> tmpMarked(isMarked_);
    
    // visit function
    std::function<void(const T &)> visit = [&](const T &v)
    {
        if (tmpMarked.at(v))
        {
            HADRON_ERROR(Range, "cannot topologically sort a cyclic graph");
        }
        if (!isMarked(v))
        {
            std::vector<T> child = getChildren(v);
            
            tmpMarked[v] = true;
            std::shuffle(child.begin(), child.end(), gen);
            for (auto &c: child)
            {
                visit(c);
            }
            mark(v);
            tmpMarked[v] = false;
            buf.push(v);
        }
    };
    
    // reset temporary marks
    for (auto &v: tmpMarked)
    {
        tmpMarked.at(v.first) = false;
    }
    
    // loop on unmarked vertices
    unmarkAll();
    vPt = getRandomUnmarked(gen);
    while (vPt)
    {
        visit(*vPt);
        vPt = getRandomUnmarked(gen);
    }
    unmarkAll();
    
    // create result vector
    while (!buf.empty())
    {
        res.push_back(buf.top());
        buf.pop();
    }
    
    return res;
}

// generate all possible topological sorts
// Y. L. Varol & D. Rotem, Comput. J. 24(1), pp. 83–84, 1981
// http://comjnl.oupjournals.org/cgi/doi/10.1093/comjnl/24.1.83
// complexity: O(V*log(V)) (from the paper, but really ?)
template <typename T>
std::vector<std::vector<T>> Graph<T>::allTopoSort(void)
{
    std::vector<std::vector<T>>    res;
    std::map<T, std::map<T, bool>> iMat;
    
    // create incidence matrix
    for (auto &v1: isMarked_)
    for (auto &v2: isMarked_)
    {
        iMat[v1.first][v2.first] = false;
    }
    for (auto &v: isMarked_)
    {
        auto cVec = getChildren(v.first);
        
        for (auto &c: cVec)
        {
            iMat[v.first][c] = true;
        }
    }
    
    // generate initial topological sort
    res.push_back(topoSort());
    
    // generate all other topological sorts by permutation
    std::vector<T>            p = res[0];
    const unsigned int        n = size();
    std::vector<unsigned int> loc(n);
    unsigned int              i, k, k1;
    T                         obj_k, obj_k1;
    bool                      isFinal;
    
    for (unsigned int j = 0; j < n; ++j)
    {
        loc[j] = j;
    }
    i = 0;
    while (i < n-1)
    {
        k      = loc[i];
        k1     = k + 1;
        obj_k  = p[k];
        if (k1 >= n)
        {
            isFinal = true;
            obj_k1  = obj_k;
        }
        else
        {
            isFinal = false;
            obj_k1  = p[k1];
        }
        if (iMat[res[0][i]][obj_k1] or isFinal)
        {
            for (unsigned int l = k; l >= i + 1; --l)
            {
                p[l]   = p[l-1];
            }
            p[i]   = obj_k;
            loc[i] = i;
            i++;
        }
        else
        {
            p[k]   = obj_k1;
            p[k1]  = obj_k;
            loc[i] = k1;
            i      = 0;
            res.push_back(p);
        }
    }
    
    return res;
}

// build depedency matrix from topological sorts ///////////////////////////////
// complexity: something like O(V^2*log(V!))
template <typename T>
std::map<T, std::map<T, bool>>
makeDependencyMatrix(const std::vector<std::vector<T>> &topSort)
{
    std::map<T, std::map<T, bool>> m;
    const std::vector<T>           &vList = topSort[0];
    
    for (auto &v1: vList)
    for (auto &v2: vList)
    {
        bool dep = true;
        
        for (auto &t: topSort)
        {
            auto i1 = std::find(t.begin(), t.end(), v1);
            auto i2 = std::find(t.begin(), t.end(), v2);
            
            dep = dep and (i1 - i2 > 0);
            if (!dep) break;
        }
        m[v1][v2] = dep;
    }
    
    return m;
}

END_HADRONS_NAMESPACE

#endif // Hadrons_Graph_hpp_