FullComponentStore.h

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#pragma once
 
#include <ogdf/basic/NodeArray.h>
#include <ogdf/graphalg/steiner_tree/EdgeWeightedGraphCopy.h>
 
namespace ogdf {
namespace steiner_tree {
 
#define OGDF_FULLCOMPONENTSTORE_REMOVE_IN_GRAPH_REPRESENTATION_ALSO // unnecessary but may save memory
 
template<typename T, typename ExtraDataType = void>
class FullComponentStore {
protected:
    const EdgeWeightedGraph<T>& m_originalGraph; 
    const List<node>& m_terminals; 
    const NodeArray<bool>& m_isTerminal; 
    EdgeWeightedGraph<T> m_graph; 
    NodeArray<node> m_nodeCopy, 
            m_nodeOrig; 
 
    template<class Y, class Enable = void> // Metadata without extra data
    struct Metadata {
        adjEntry start; 
        Array<node> terminals; 
        T cost; 
 
        Metadata() : start(nullptr), terminals(0), cost(0) { }
    };
 
    template<class Y> // Metadata with extra data
    struct Metadata<Y, typename std::enable_if<!std::is_void<Y>::value>::type> {
        adjEntry start; 
        Array<node> terminals; 
        T cost; 
        Y extra;
 
        Metadata() : start(nullptr), terminals(0), cost(0) { }
    };
 
    ArrayBuffer<Metadata<ExtraDataType>> m_components; 
 
    void traverseOverDegree2Nonterminals(node& uO, T& weight, EdgeArray<bool>& marked, adjEntry adj,
            const EdgeWeightedGraphCopy<T>& comp) const {
        while (m_nodeCopy[uO] == nullptr && !m_isTerminal[uO]) {
            OGDF_ASSERT(comp.copy(uO)->degree() == 2);
            adj = adj->twin()->cyclicSucc();
            OGDF_ASSERT(comp.original(adj->theNode()) == uO);
            edge e2 = adj->theEdge();
            marked[e2] = true;
            weight += comp.weight(e2);
            uO = comp.original(adj->twinNode());
        }
    }
 
    void copyEdgesWithSimplifiedPaths(Metadata<ExtraDataType>& data,
            const EdgeWeightedGraphCopy<T>& comp, const ArrayBuffer<node>& nonterminals) {
        EdgeArray<bool> marked(comp, false);
        for (node v : nonterminals) {
            for (adjEntry adj : comp.copy(m_nodeOrig[v])->adjEntries) {
                edge e = adj->theEdge();
                if (!marked[e]) {
                    marked[e] = true;
                    node vO = comp.original(adj->theNode());
                    OGDF_ASSERT(m_nodeCopy[vO] != nullptr);
                    node uO = comp.original(adj->twinNode());
                    T weight(comp.weight(e));
 
                    traverseOverDegree2Nonterminals(uO, weight, marked, adj, comp);
 
                    edge eC = m_graph.newEdge(m_nodeCopy[uO], m_nodeCopy[vO], weight);
                    data.cost += weight;
                    if (m_isTerminal[uO]) {
                        data.start = eC->adjSource();
                    }
                }
            }
        }
#ifdef OGDF_DEBUG
        for (edge e : comp.edges) {
            OGDF_ASSERT(marked[e] == true);
        }
#endif
    }
 
    void copyEdges(Metadata<ExtraDataType>& data, const EdgeWeightedGraphCopy<T>& comp) {
        for (edge e : comp.edges) {
            node uO = comp.original(e->source());
            node vO = comp.original(e->target());
            T weight = comp.weight(e);
            edge eC = m_graph.newEdge(m_nodeCopy[uO], m_nodeCopy[vO], weight);
            data.cost += weight;
            if (m_isTerminal[uO]) {
                data.start = eC->adjSource();
            } else if (m_isTerminal[vO]) {
                data.start = eC->adjTarget();
            }
        }
    }
 
public:
    FullComponentStore(const EdgeWeightedGraph<T>& G, const List<node>& terminals,
            const NodeArray<bool>& isTerminal)
        : m_originalGraph(G)
        , m_terminals(terminals)
        , m_isTerminal(isTerminal)
        , m_nodeCopy(G, nullptr)
        , m_nodeOrig(m_graph) {
        for (node v : m_terminals) {
            node u = m_graph.newNode();
            m_nodeCopy[v] = u;
            m_nodeOrig[u] = v;
        }
    }
 
    void insert(const EdgeWeightedGraphCopy<T>& comp) {
        OGDF_ASSERT(!comp.empty());
        OGDF_ASSERT(isTree(comp));
 
        // we temporarily use m_nodeCopy for nonterminals (with degree > 2) also
        ArrayBuffer<node> nonterminals(comp.numberOfNodes() / 2);
 
        // add all nonterminals with degree > 2 of comp to m_graph
        // and find terminals
        Metadata<ExtraDataType> data;
        bool existNoncritical = false;
        for (node v : comp.nodes) {
            node vO = comp.original(v);
            if (m_nodeCopy[vO] == nullptr) {
                OGDF_ASSERT(v->degree() >= 2);
                if (v->degree() > 2) {
                    node vC = m_graph.newNode();
                    m_nodeCopy[vO] = vC;
                    m_nodeOrig[vC] = vO;
                    nonterminals.push(vC);
                } else {
                    existNoncritical = true;
                }
            } else {
                data.terminals.grow(1, vO);
            }
        }
        data.terminals.quicksort(GenericComparer<node, int>([](node v) { return v->index(); }));
 
        // add all edges of comp to m_graph
        // and find start adjEntry
        if (existNoncritical) {
            if (nonterminals.empty()) {
                OGDF_ASSERT(data.terminals.size() == 2);
                OGDF_ASSERT(data.cost == 0);
                for (edge e : comp.edges) {
                    data.cost += comp.weight(e);
                }
                edge eC = m_graph.newEdge(m_nodeCopy[data.terminals[0]],
                        m_nodeCopy[data.terminals[1]], data.cost);
                data.start = eC->adjSource();
            } else {
                copyEdgesWithSimplifiedPaths(data, comp, nonterminals);
            }
        } else {
            copyEdges(data, comp);
        }
        OGDF_ASSERT(data.start != nullptr);
 
        // cleanup m_nodeCopy (only terminals should be set)
        for (node vC : nonterminals) {
            m_nodeCopy[m_nodeOrig[vC]] = nullptr;
        }
 
        m_components.push(data);
    }
 
    void remove(int id) {
#ifdef OGDF_FULLCOMPONENTSTORE_REMOVE_IN_GRAPH_REPRESENTATION_ALSO
        auto& comp = m_components[id];
        if (comp.terminals.size() == 2) {
            m_graph.delEdge(comp.start->theEdge());
        } else {
            ArrayBuffer<node> stack(2 * comp.terminals.size() - 3);
            stack.push(comp.start->twinNode());
            m_graph.delEdge(comp.start->theEdge());
            while (!stack.empty()) {
                const node v = stack.popRet();
                if (!isTerminal(v)) {
                    for (adjEntry adj : v->adjEntries) {
                        stack.push(adj->twinNode());
                    }
                    m_graph.delNode(v);
                }
            }
        }
#endif
        if (m_components.size() == id + 1) {
            m_components.pop();
        } else {
            m_components[id] = m_components.popRet();
        }
    }
 
    int size() const { return m_components.size(); }
 
    bool isEmpty() const { return m_components.empty(); }
 
    const Array<node>& terminals(int id) const {
        OGDF_ASSERT(id >= 0);
        OGDF_ASSERT(id < m_components.size());
        return m_components[id].terminals;
    }
 
    bool isTerminal(int id, node t) const {
        OGDF_ASSERT(id >= 0);
        OGDF_ASSERT(id < m_components.size());
        return m_components[id].terminals.linearSearch(t) != -1;
    }
 
    bool isTerminal(node v) const { return m_isTerminal[m_nodeOrig[v]]; }
 
    T cost(int i) const {
        OGDF_ASSERT(i >= 0);
        OGDF_ASSERT(i < m_components.size());
        return m_components[i].cost;
    }
 
    adjEntry start(int i) const {
        OGDF_ASSERT(i >= 0);
        OGDF_ASSERT(i < m_components.size());
        return m_components[i].start;
    }
 
    const EdgeWeightedGraph<T>& graph() const { return m_graph; }
 
    node original(node v) const {
        OGDF_ASSERT(m_nodeOrig[v] != nullptr);
        return m_nodeOrig[v];
    }
 
    template<typename Fun>
    void foreachAdjEntry(int i, Fun f) const {
        adjEntry start = m_components[i].start;
        int size = m_components[i].terminals.size();
        if (size == 2) {
            f(start->twin());
            return;
        }
        // size >= 3: do DFS over nonterminals (terminals are only leaves)
        ArrayBuffer<adjEntry> stack(2 * size - 2);
        stack.push(start);
        while (!stack.empty()) {
            const adjEntry back = stack.popRet()->twin();
            f(back);
            if (!this->isTerminal(back->theNode())) {
                for (adjEntry adj = back->cyclicSucc(); adj != back; adj = adj->cyclicSucc()) {
                    stack.push(adj);
                }
            }
        }
    }
 
    // \brief Do f(v) for each (original) node v of degree at least 3 in component with given id
    template<typename Fun>
    void foreachNode(int id, Fun f) const {
        f(original(start(id)->theNode()));
        foreachAdjEntry(id, [&](adjEntry back) { f(original(back->theNode())); });
    }
 
    // \brief Do f(e) for each (original) edge e in component with given id
    template<typename Fun>
    void foreachEdge(int id, const NodeArray<NodeArray<edge>>& pred, Fun f) const {
        foreachAdjEntry(id, [&](adjEntry back) {
            const node u = original(back->twinNode());
            for (node v = original(back->theNode()); pred[u][v]; v = pred[u][v]->opposite(v)) {
                f(pred[u][v]);
            }
        });
    }
 
    // \brief Do f(v) for each node v (also of degree 2) in component with given id
    template<typename Fun>
    void foreachNode(int id, const NodeArray<NodeArray<edge>>& pred, Fun f) const {
        if (m_components[id].terminals.size() == 3) {
            // use a variant that works when only pred[t] has been filled for all terminals t
            adjEntry start = m_components[id].start;
            const node c = start->twinNode();
            f(original(c));
            for (adjEntry adj : c->adjEntries) {
                const node u = original(adj->twinNode());
                node v = original(c);
                while (v != u) {
                    v = pred[u][v]->opposite(v);
                    f(v);
                }
            }
            return;
        }
        f(original(start(id)->theNode()));
        foreachAdjEntry(id, [&](adjEntry back) {
            const node u = original(back->twinNode());
            for (node v = original(back->theNode()); pred[u][v]; v = pred[u][v]->opposite(v)) {
                f(v);
            }
        });
    }
};
 
template<typename T, typename ExtraDataType>
class FullComponentWithExtraStore : public FullComponentStore<T, ExtraDataType> {
public:
    using FullComponentStore<T, ExtraDataType>::FullComponentStore;
 
    ExtraDataType& extra(int i) {
        OGDF_ASSERT(i >= 0);
        OGDF_ASSERT(i < this->m_components.size());
        return this->m_components[i].extra;
    }
 
    const ExtraDataType& extra(int i) const {
        OGDF_ASSERT(i >= 0);
        OGDF_ASSERT(i < this->m_components.size());
        return this->m_components[i].extra;
    }
};
 
template<typename T>
struct LossMetadata {
    T loss; 
    List<edge> bridges; 
 
    LossMetadata() : loss(0), bridges() { }
};
 
template<typename T>
class FullComponentWithLossStore : public FullComponentWithExtraStore<T, LossMetadata<T>> {
protected:
    NodeArray<node> m_lossTerminal;
 
    node findLossTerminal(const node u, const NodeArray<edge>& pred) {
        if (!m_lossTerminal[u] && pred[u]) {
            m_lossTerminal[u] = findLossTerminal(pred[u]->opposite(u), pred);
        }
 
        return m_lossTerminal[u];
    }
 
public:
    using FullComponentWithExtraStore<T, LossMetadata<T>>::FullComponentWithExtraStore;
 
    void computeAllLosses() {
        m_lossTerminal.init(this->m_graph, nullptr);
 
        // add zero-cost edges between all terminals (to be removed later),
        // and set m_lossTerminal mapping for terminals
        List<edge> zeroEdges;
        const node s = this->m_terminals.front();
        const node sC = this->m_nodeCopy[s];
        m_lossTerminal[sC] = s;
        for (ListConstIterator<node> it = this->m_terminals.begin().succ(); it.valid(); ++it) {
            const node v = *it;
            const node vC = this->m_nodeCopy[v];
            m_lossTerminal[vC] = v;
            zeroEdges.pushBack(this->m_graph.newEdge(sC, vC, 0));
        }
 
        // compute minimum spanning tree
        NodeArray<edge> pred(this->m_graph);
        EdgeArray<bool> isLossEdge(this->m_graph, false);
        computeMinST(sC, this->m_graph, this->m_graph.edgeWeights(), pred, isLossEdge);
 
        // remove zero-cost edges again
        for (edge e : zeroEdges) {
            this->m_graph.delEdge(e);
        }
 
        // find loss bridges and compute loss value
        for (int id = 0; id < this->size(); ++id) {
            this->foreachAdjEntry(id, [&](adjEntry adj) {
                edge e = adj->theEdge();
                if (!isLossEdge[e]) {
                    this->extra(id).bridges.pushBack(e);
                    findLossTerminal(e->source(), pred);
                    findLossTerminal(e->target(), pred);
                } else {
                    this->extra(id).loss += this->m_graph.weight(e);
                }
            });
        }
    }
 
    T loss(int id) const { return this->extra(id).loss; }
 
    const List<edge>& lossBridges(int id) const { return this->extra(id).bridges; }
 
    node lossTerminal(node v) const {
        OGDF_ASSERT(m_lossTerminal.valid());
        return m_lossTerminal[v];
    }
};
 
}
}