Exemplo n.º 1
0
 public DominatingInducedMatching(int n)
     : base(n)
 {
     Sigma = new BitSet(0, MaxSize) { 1 };
     Rho = new BitSet(0, MaxSize) { 0 };
     Rho = !Rho;
 }
Exemplo n.º 2
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 public IndependentDominatingSet(int n)
     : base(n)
 {
     Sigma = new BitSet(0, MaxSize) { 0 };
     Rho = new BitSet(0, MaxSize) { 0 };
     Rho = !Rho;
 }
Exemplo n.º 3
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        // Uses depth-first search to check if the graph induced by the subgraph given as a parameter is connected
        // In other words, we retreive all edges from the original graph and check the subgraph for connectedness
        public static bool Connected(Graph graph, BitSet subgraph)
        {
            // Vertices that are visited
            Set<int> visited = new Set<int>();

            // Stack of vertices yet to visit
            Stack<int> stack = new Stack<int>();

            // Initial vertex
            int s = subgraph.First();
            stack.Push(s);

            // Continue while there are vertices on the stack
            while (stack.Count > 0)
            {
                int v = stack.Pop();

                // If we have not encountered this vertex before, then we check for all neighbors if they are part of the subgraph
                // If a neighbor is part of the subgraph it means that we have to push it on the stack to explore it at a later stage
                if (!visited.Contains(v))
                {
                    visited.Add(v);

                    foreach (int w in graph.OpenNeighborhood(v))
                        if (subgraph.Contains(w))
                            stack.Push(w);
                }
            }

            // If we visited an equal number of vertices as there are vertices in the subgraph then the subgraph is connected
            return visited.Count == subgraph.Count;
        }
Exemplo n.º 4
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 public DominatingSet(int n)
     : base(n)
 {
     Sigma = new BitSet(0, MaxSize);
     Sigma = !Sigma;
     Rho = new BitSet(0, MaxSize) { 0 };
     Rho = !Rho;
 }
Exemplo n.º 5
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        // Basic constructor for a dNeighborhood
        public dNeighborhood(BitSet vector)
        {
            Occurrences = new Dictionary<int, int>();
            Vector = vector;

            foreach (int v in Vector)
                Occurrences[v] = 0;
        }
Exemplo n.º 6
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        // Counts the number of independent sets in a graph, such that:
        // - The vertices in P are legal choices for our IS, initially set to all vertices in the graph
        // - None of the vertices in X are used, initially empty
        // The performDFS boolean is used to check if we should perform a check for connectedness on this level of the recursion
        private static long Compute(Graph graph, BitSet P, BitSet X, bool performDFS)
        {
            // Base case, when P and X are both empty we cannot expand the IS
            if (P.IsEmpty && X.IsEmpty)
                return 1;

            // Base case, if a vertex w in X has no neighbor in P, then it means that this IS will never get maximal
            // since we could always include w. Thus, the IS will not be valid and we return 0.
            foreach (int w in X)
                if ((graph.OpenNeighborhood(w) * P).IsEmpty)
                    return 0;

            long count = 0;

            // If a DFS is needed we check if the graph induced by (P + X) is still connected.
            // If the graph is disconnected, in components c1,...,cn then we can simply count the IS of all these components
            // after which we simply multiply these numbers.
            if (performDFS)
            {
                if (!DepthFirstSearch.Connected(graph, P + X))
                {
                    count = 1;

                    foreach (BitSet component in DepthFirstSearch.ConnectedComponents(graph, P + X))
                        count *= Compute(graph, component * P, component * X, false);

                    return count;
                }
            }

            // Select a pivot in P to branch on
            // In this case we pick the vertex with the largest degree
            int maxDegree = -1; ;
            int pivot = -1;
            foreach (int u in P)
            {
                int deg = graph.Degree(u);
                if (deg > maxDegree)
                {
                    maxDegree = deg;
                    pivot = u;
                }
            }

            // There should always be a pivot after the selection procedure
            if (pivot == -1)
                throw new Exception("Pivot has not been selected");

            // We branch on the pivot, one branch we include the pivot in the IS.
            // This might possibly disconnect the subgraph G(P + X), thus we set the performDFS boolean to true.
            count = Compute(graph, P - graph.ClosedNeighborhood(pivot), X - graph.OpenNeighborhood(pivot), true);

            // One branch we exclude the pivot of the IS. This will not cause the graph to get possibly disconnected
            count += Compute(graph, P - pivot, X + pivot, false);

            return count;
        }
Exemplo n.º 7
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        private static List<int> ComputeSequence(Graph graph, BitSet connectedComponent, CandidateStrategy candidateStrategy, int init, out int value)
        {
            int n = graph.Size;
            List<int> sequence = new List<int>() { init };
            BitSet left = new BitSet(0, n) { init };
            BitSet right = connectedComponent - init;

            // Initially we store the empty set and the set with init as the representative, ie N(init) * right
            Set<BitSet> UN_left = new Set<BitSet>() { new BitSet(0, n), graph.OpenNeighborhood(init) * right };
            value = int.MinValue;
            while (!right.IsEmpty)
            {
                Set<BitSet> UN_chosen = new Set<BitSet>();
                int chosen = Heuristics.TrivialCases(graph, left, right);

                if (chosen != -1)
                {
                    UN_chosen = IncrementUN(graph, left, UN_left, chosen);
                }
                // If chosen has not been set it means that no trivial case was found
                // Depending on the criteria for the next vertex we call a different algorithm
                else
                {
                    BitSet candidates = Heuristics.Candidates(graph, left, right, candidateStrategy);

                    int min = int.MaxValue;

                    foreach (int v in candidates)
                    {
                        Set<BitSet> UN_v = IncrementUN(graph, left, UN_left, v);
                        if (UN_v.Count < min)
                        {
                            chosen = v;
                            UN_chosen = UN_v;
                            min = UN_v.Count;
                        }
                    }
                }

                // This should never happen
                if (chosen == -1)
                    throw new Exception("No vertex is chosen for next step in the heuristic");

                // Add/remove the next vertex in the appropiate sets
                sequence.Add(chosen);
                left.Add(chosen);
                right.Remove(chosen);
                UN_left = UN_chosen;
                value = Math.Max(UN_chosen.Count, value);
            }

            return sequence;
        }
Exemplo n.º 8
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        // This constructor returns a new bipartite graph by putting all vertices in 'left' on one side, and 'right' on the other side
        // There will be an edge between two vertices if there was an edge in the original graph
        public BipartiteGraph(Graph graph, BitSet _left, BitSet _right)
            : this(_left, _right, _left.Count + _right.Count)
        {
            Dictionary<int, int> mapping = new Dictionary<int, int>();
            int i = 0;

            foreach (int v in left + right)
                mapping[v] = i++;

            foreach (int v in left)
                foreach (int w in graph.OpenNeighborhood(v) * right)
                    Connect(mapping[v], mapping[w]);
        }
Exemplo n.º 9
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        /*************************/
        // Construction
        /*************************/
        // Constructor for a new graph of size n
        public Graph(int n)
        {
            vertices = new BitSet(0, n);
            AdjacencyMatrix = new BitSet[n];

            Size = n;

            for (int i = 0; i < n; i++)
            {
                vertices.Add(i);
                AdjacencyMatrix[i] = new BitSet(0, n);
            }
        }
        private void FillTable(Graph graph, List<int> sequence)
        {
            int n = graph.Size;

            // Processed vertices
            BitSet left = new BitSet(0, n);

            // Unprocessed vertices
            BitSet right = graph.Vertices;

            // Lists of representatives that we keep track of on each level of the algorithm
            LinearRepresentativeList reps = new LinearRepresentativeList();

            // Initial insertions, the empty set always has the empty neighborhood set as a representative initially
            reps.Update(new BitSet(0, n), new BitSet(0, n));

            for (int i = 0; i < sequence.Count; i++)
            {
                /// We give v the possibility to be a representative instead of being contained in neighborhoods
                int v = sequence[i];

                // Actually move v from one set to the other set
                left.Add(v);
                right.Remove(v);

                // We don't want to disturb any pointers so we create new empty datastructures to save everything for the next iteration
                LinearRepresentativeList nextReps = new LinearRepresentativeList();

                // We are iterating over all representatives saved inside the list of the previous step. For each entry there are only two possibilities to create a new neighborhood
                foreach (BitSet representative in reps)
                {
                    // Case 1: The neighborhood possibly contained v (thus v has to be removed), but is still valid
                    BitSet neighborhood = reps.GetNeighborhood(representative) - v;
                    nextReps.Update(representative, neighborhood);

                    // Case 2: The union of the old neighborhood, together with v's neighborhood, creates a new entry. The representative is uniond together with v and saved.
                    BitSet representative_ = representative + v;
                    BitSet neighborhood_ = neighborhood + (graph.OpenNeighborhood(v) * right);
                    nextReps.Update(representative_, neighborhood_);
                }

                // Update the values for the next iteration
                reps = nextReps;

                // Save the maximum size that we encounter during all iterations; this will be the boolean dimension of the graph.
                MaxDimension = Math.Max(MaxDimension, reps.Count);

                // Save the representatives at the current cut in the table
                Table[left.Copy()] = reps;
            }
        }
Exemplo n.º 11
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        // Builds a neighborhood for a set X from the ground on up, without relying on what has been saved previously in O(n^2) time
        public dNeighborhood(BitSet X, BitSet vector, Graph graph)
        {
            // O(n) time copy
            Vector = vector.Copy();
            Occurrences = new Dictionary<int, int>();

            // Loops in O(|Vector|) time over all vertices in the vector
            foreach (int v in Vector)
            {
                // Bitset operation of O(n) time
                BitSet nv = graph.OpenNeighborhood(v) * X;
                Occurrences[v] = Math.Min(nv.Count, dValue);
            }
        }
Exemplo n.º 12
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        // Implementation of Algorithm 1 of 'Fast dynamic programming for locally checkable vertex subset and vertex partitioning problems' (Bui-Xuan et al.)
        // Used to compute the representatives and their corresponding dNeighborhoods for a given node of the decomposition tree
        private void FillTable(Graph graph, BitSet cut)
        {
            int n = graph.Size;
            BitSet _cut = graph.Vertices - cut;

            // Lists of representatives that we keep track of on each level of the algorithm
            RepresentativeList representatives = new RepresentativeList();
            RepresentativeList lastLevel = new RepresentativeList();

            // Initial insertions, the empty set always has the empty neighborhood set as a representative initially
            dNeighborhood dInitial = new dNeighborhood(_cut);
            representatives.Update(new BitSet(0, n), dInitial);
            lastLevel.Update(new BitSet(0, n), dInitial);

            while (lastLevel.Count > 0)
            {
                RepresentativeList nextLevel = new RepresentativeList();
                foreach (BitSet r in lastLevel)
                {
                    foreach (int v in cut)
                    {
                        // avoid that r_ = r, since we already saved all sets of that size
                        if (r.Contains(v))
                            continue;

                        BitSet r_ = r + v;
                        dNeighborhood dn = representatives.GetNeighborhood(r).CopyAndUpdate(graph, v);

                        if (!representatives.ContainsNeighborhood(dn) && !dn.Equals(representatives.GetNeighborhood(r)))
                        {
                            nextLevel.Update(r_, dn);
                            representatives.Update(r_, dn);
                        }
                    }
                }

                // Update the values for the next iteration
                lastLevel = nextLevel;
            }

            // Save the representatives at the current cut in the table
            Table[cut.Copy()] = representatives;

            // Save the maximum size that we encounter during all iterations; this will be the boolean dimension of the graph is d = 1.
            MaxDimension = Math.Max(MaxDimension, representatives.Count);
        }
Exemplo n.º 13
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        // Counts the number of independent sets in a graph, such that:
        // - All vertices in R are included in the independent set, initially empty
        // - Some of the vertices in P are included in the independent set, initially all vertices of the graph
        // - None of the vertices in X are included in the independent set, initially empty
        private static int Compute(Graph graph, BitSet R, BitSet P, BitSet X)
        {
            // Base case, when P and X are both empty we cannot expand the IS
            if (P.IsEmpty && X.IsEmpty)
                return 1;

            int count = 0;
            BitSet copy = P.Copy();

            // Foreach vertex v in P we include it in the IS and compute how many maximal IS will include v by going into recursion.
            foreach (int v in copy)
            {
                count += Compute(graph, R + v, P - graph.ClosedNeighborhood(v), X - graph.OpenNeighborhood(v));
                P.Remove(v);
                X.Add(v);
            }

            return count;
        }
Exemplo n.º 14
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        // Returns all connected components in a certain subgraph, where we define a subgraph by the vertices that are contained in it
        // We apply multiple dfs searches to find all connected parts of the graph
        public static List<BitSet> ConnectedComponents(Graph graph, BitSet subgraph)
        {
            // Each connected component is defined as a bitset, thus the result is a list of these bitsets
            List<BitSet> result = new List<BitSet>();

            // Working stack for the dfs algorithm
            Stack<int> stack = new Stack<int>();

            // Each vertex of the subgraph will either be explored, or it will be the starting point of a new dfs search
            BitSet todo = subgraph.Copy();

            while (!todo.IsEmpty)
            {
                int s = todo.First();
                stack.Push(s);

                // Start tracking the new component
                BitSet component = new BitSet(0, graph.Size);

                // Default dfs exploring part of the graph
                while (stack.Count > 0)
                {
                    int v = stack.Pop();

                    // If we have not encountered this vertex before (meaning it isn't in this component), then we check for all neighbors if they are part of the subgraph
                    // If a neighbor is part of the subgraph it means that we have to push it on the stack to explore it at a later stage for this component
                    if (!component.Contains(v))
                    {
                        component.Add(v);

                        // Remove this vertex from the 'todo' list, since it can never be the starting point of a new component
                        todo.Remove(v);

                        foreach (int w in graph.OpenNeighborhood(v))
                            if (subgraph.Contains(w))
                                stack.Push(w);
                    }
                }
                // The whole connected component has been found, so we can add it to the list of results
                result.Add(component);
            }
            return result;
        }
Exemplo n.º 15
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        // Constructs the actual width values
        // The idea is the following: If we want to know the optimal width for a certain cut A, thus Width[A], then we can obtain this by
        // either taking the max(Cuts[A], the minimum over all widths of Width[A - a]), which is our recurrence relation.
        private static void ConstructSequence(Graph graph, BitSet A)
        {
            // min saves the minimum size of all neighborhoods of the cut [A - a], where a can be any vertex in A
            long min = long.MaxValue;

            // v will be the optimal choice to leave out in the previous iteration in order to obtain A's full neighborhood
            int v = -1;

            foreach (int a in A)
            {
                BitSet previous = A - a;

                // If we have not constructed the previous step yet, then go in recursion and do so
                if (!Neighborhoods.ContainsKey(previous))
                    ConstructSequence(graph, previous);

                // Save the minimum value
                if (Width[previous] < min)
                {
                    min = Width[previous];
                    v = a;
                }
            }

            // Obtain the neighborhood of v
            BitSet nv = graph.OpenNeighborhood(v) * (graph.Vertices - A);

            // We save the full set of neighborhood vertices at cut A. It does not matter that v was chosen arbitrarely; we always end up in the same collection of neighboring vertices for the set A
            Set<BitSet> un = new Set<BitSet>();
            foreach (BitSet _base in Neighborhoods[A - v])
            {
                un.Add(_base - v);          // previous neighbor without v is a possible new neighborhood
                un.Add((_base - v) + nv);   // previous neighbor without v, unioned with the neighborhood of v is a possible new neighborhood
            }

            // Save all entries
            Neighborhoods[A] = un;              // List of all neighbors at cut A
            Cuts[A] = Neighborhoods[A].Count;   // Dimension at this cut
            Width[A] = Math.Max(min, Cuts[A]);  // Actual possible width to get to this cut
        }
Exemplo n.º 16
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        // Parses a decomposition given the filename of the decomposition and the graph files.
        public static Decomposition ParseDecomposition(string decompositionFilename, string graphFilename)
        {
            Graph graph = ParseGraph(graphFilename);
            StreamReader sr = new StreamReader(decompositionFilename);
            string line;
            Tree tree = new Tree();

            // Each line is simply an integer, which is the sequence of the linear decomposition
            while ((line = sr.ReadLine()) != null)
            {
                // Skip comments
                if (line.StartsWith("c ")) continue;

                string[] s = line.Trim().Split(' ');
                BitSet node = new BitSet(0, graph.Size);
                foreach (string vertex in s)
                    node.Add(int.Parse(vertex) - 1); // -1 because internally we work with [0,...,n)
                tree.Insert(node);
            }

            return new Decomposition(graph, tree);
        }
Exemplo n.º 17
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        // Counts the number of independent sets in a graph, such that:
        // - All vertices in R are included in the independent set, initially empty
        // - Some of the vertices in P are included in the independent set, initially all vertices of the graph
        // - None of the vertices in X are included in the independent set, initially empty
        private static long Compute(Graph graph, BitSet R, BitSet P, BitSet X)
        {
            // Base case, when P and X are both empty we cannot expand the IS
            if (P.IsEmpty && X.IsEmpty)
                return 1;

            long count = 0;
            int pivot = -1;
            int min = int.MaxValue;

            // Procedure to find a pivot
            // The idea is that in any maximal IS, either vertex u or a neighbor of u is included (else we could expand by adding u to the IS)
            // We find the u with the smallest neighborhood, so that we will keep the number of branches low
            foreach (int u in (P + X))
            {
                int size = (P * graph.OpenNeighborhood(u)).Count;
                if (size < min)
                {
                    min = size;
                    pivot = u;
                }
            }

            // There should always be a pivot after the selection procedure, else P and X should both have been empty
            if (pivot == -1)
                throw new Exception("Pivot has not been selected");

            // Foreach vertex v in the set containing the legal choices of the the closed neighborhood of the pivot,
            // we include each choice in the IS and compute how many maximal IS will include v by going into recursion
            foreach (int v in (P * graph.ClosedNeighborhood(pivot)))
            {
                count += Compute(graph, R + v, P - graph.ClosedNeighborhood(v), X - graph.OpenNeighborhood(v));
                P.Remove(v);
                X.Add(v);
            }

            return count;
        }
Exemplo n.º 18
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        /*************************/
        // Trivial cases
        /*************************/
        public static int TrivialCases(Graph graph, BitSet left, BitSet right)
        {
            int chosen = -1;

            // Check if any vertex in right belongs to one of the trivial cases, if yes then we can add this vertex directly to the sequence
            foreach (int v in right)
            {
                // Trivial case 1. If the neighbors of a vertex v in right are all contained in left, then select v
                // What this means is that v has an empty neighborhood, thus it will not add anything to the boolean-dimension
                if ((graph.OpenNeighborhood(v) - left).IsEmpty)
                {
                    chosen = v;

                    break;
                }

                bool stop = false;
                // 2. If there are two vertices, v in right and u in left, such that N(v) * right == (N(u)\v) * right,
                // then v is selected as our next vertex
                // What this means is that all neighbors of v are already 'represented' by u, thus making the choice for v will not add anything to the dimension
                foreach (int u in left)
                {
                    BitSet nv = graph.OpenNeighborhood(v) * right;  // N(v) * right
                    BitSet nu = (graph.OpenNeighborhood(u) - v) * right;    // (N(u)\v) * right
                    if (nv.Equals(nu))
                    {
                        chosen = v;
                        stop = true;
                        break;
                    }
                }

                if (stop) break;
            }

            return chosen;
        }
Exemplo n.º 19
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 public int this[BitSet representative, int k]
 {
     get
     {
         if (!Data[k].ContainsKey(representative))
             return 0;
         return Data[k][representative];
     }
     set
     {
         Data[k][representative.Copy()] = value;
     }
 }
Exemplo n.º 20
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        public dNeighborhood CopyAndUpdateVector(BitSet vector, bool increment)
        {
            // initialize an empty dNeighborhood in O(|Vector|) time
            dNeighborhood nx = new dNeighborhood(vector);

            BitSet iterateOver = increment ? Vector : vector;
            foreach (int v in iterateOver)
                nx.Occurrences[v] = Occurrences[v];

            return nx;
        }
Exemplo n.º 21
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 /*************************/
 // Candidate strategy
 /*************************/
 public static BitSet Candidates(Graph graph, BitSet left, BitSet right, CandidateStrategy candidateStrategy)
 {
     BitSet nl = graph.Neighborhood(left) * right;
     return candidateStrategy == CandidateStrategy.All ?
         right.Copy() : (nl + graph.Neighborhood(nl)) * right;
 }
Exemplo n.º 22
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        public static void Compute(LinearDecomposition decomposition)
        {
            Graph graph = decomposition.Graph;
            List<int> sequence = decomposition.Sequence;
            int n = graph.Size;

            BitSet right = graph.Vertices;
            BitSet left = new BitSet(0, n);

            LookupTable table = new LookupTable(n);
            LinearRepresentativeTable cuts = new LinearRepresentativeTable(graph, sequence);

            table[new BitSet(0, n), 0] = 1;
            table[new BitSet(0, n), 1] = 0;

            for (int i = 0; i < sequence.Count; i++)
            {
                int v = sequence[i];

                left.Add(v);
                right.Remove(v);

                LinearRepresentativeList LRw = cuts[left];

                LinearRepresentativeList LRa = cuts[left - v];

                LookupTable newTable = new LookupTable(n);

                foreach (BitSet ra in LRa)
                {
                    BitSet nra = graph.Neighborhood(ra) * right;
                    BitSet rw = LRw.GetRepresentative(nra);

                    int maxValue = int.MinValue;
                    int limit = (left - v).Count;
                    for (int k = 0; k <= limit; k++)
                        if (table[ra, k] > 0)
                            maxValue = Math.Max(maxValue, k);

                    for (int j = 0; j <= maxValue; j++)
                    {
                        newTable[rw, j] = newTable[rw, j] + table[ra, j];
                    }

                    //------------

                    // ra + {v} is not a valid independent set
                    if (LRa.GetNeighborhood(ra).Contains(v))
                        continue;

                    //------------

                    // add {v} to the independent set
                    BitSet nrav = graph.Neighborhood(ra + v) * right;
                    BitSet rwv = LRw.GetRepresentative(nrav);

                    for (int j = 0; j <= maxValue; j++)
                    {
                        newTable[rwv, j + 1] = newTable[rwv, j + 1] + table[ra, j];
                    }
                }

                table = newTable;
            }

            return;
        }
Exemplo n.º 23
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 /*************************/
 // Basic operations
 /*************************/
 // When adding a new entry we check if the neighborhood is already contained in the set
 // If true, then we might replace the previous representative that is not connected to this neighborhood if the new one is lexicographically smaller
 public void Update(BitSet representative, dNeighborhood neighborhood)
 {
     Map.Add(representative.Copy(), neighborhood);
 }
Exemplo n.º 24
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        // Inserting a node with its parent saves us the time of finding the parent
        public void InsertWithParent(BitSet node, BitSet parent)
        {
            Parent[node] = parent;

            if (Size % 2 == 0)
            {
                if (RightChild.ContainsKey(parent))
                    throw new Exception("Inserted parent already has a leftchild");
                RightChild[parent] = node;
            }
            else
            {
                if (LeftChild.ContainsKey(parent))
                    throw new Exception("Inserted parent already has a leftchild");
                LeftChild[parent] = node;
            }

            Contained.Add(node);
        }
Exemplo n.º 25
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            // Determines the dValue given set
            // For a set x, d is defined as follows:
            // d(N) = 0
            // d(x) = 1 + min(max v in x, max v not in x)
            private static int DetermineDValue(BitSet set)
            {
                BitSet _set = !set;

                if (set.IsEmpty || _set.IsEmpty)
                    return 0;

                return 1 + Math.Min(set.Last(), _set.Last());
            }
Exemplo n.º 26
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        /*************************/
        // Basic operations
        /*************************/
        // Inserting works correctly because we assume that a node that gets newly inserted will not be in the tree already
        // By definition of boolean decompositions this is redundant and the node should be removed from the decomposition tree
        public void Insert(BitSet node)
        {
            if (Parent.ContainsKey(node))
                throw new Exception("This node already exists in the decomposition tree");

            // Check if this is the first node that we add to the collection
            if (Size == 0)
            {
                root = node;
                Contained.Add(node);
                return;
            }

            // The parent of the node that we are currently insering should be the node X that this node is a subset of, and X is has the highest index so far
            BitSet parent = new BitSet(0, 0);
            for (int i = Size - 1; i >= 0; i--)
            {
                parent = Contained[i];
                if (node.IsSubsetOf(parent))
                    break;
            }

            Parent[node] = parent;

            // The node will always be a leftchild if the previously inserted node had an even number, and vice versa
            // This assumes that we always add children of a node directly after each other
            if (Size % 2 == 0)
                RightChild[parent] = node;
            else
                LeftChild[parent] = node;

            Contained.Add(node);
        }
Exemplo n.º 27
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        // Alternative way of calculating the boolean width of a decomposition by counting the number of maximal independent sets in bipartite graphs,
        // constructed for each cut of the decomposition
        private long CalculateBooleanWidthBiPartite()
        {
            BitSet left = new BitSet(0, Graph.Size);
            BitSet right = Graph.Vertices;
            long max = int.MinValue;

            foreach (int v in Sequence)
            {
                left.Add(v);
                right.Remove(v);
                // Construct the bipartite graph
                BipartiteGraph bg = new BipartiteGraph(Graph, left, right);

                // Count the number of maximal independent sets in this bipartite graph
                max = Math.Max(max, CC_MIS.Compute(bg));
            }
            return max;
        }
Exemplo n.º 28
0
        public static int Compute(LinearDecomposition decomposition)
        {
            Graph graph = decomposition.Graph;
            int n = graph.Size;
            List<int> sequence = decomposition.Sequence;
            BitSet left = new BitSet(0, graph.Size);
            BitSet right = graph.Vertices;
            BitSet VG = graph.Vertices;

            LinearRepresentativeTable cuts = new LinearRepresentativeTable(graph, sequence);
            LookupTable table = new LookupTable();

            // first initialize the very first leaf node
            int l = sequence[0];
            left.Add(l);
            right.Remove(l);

            // Base cases
            BitSet leaf = new BitSet(0, n) { l };
            BitSet nleaf = new BitSet(0, n) { graph.OpenNeighborhood(l).First() };

            table[new BitSet(0, n), new BitSet(0, n)] = int.MaxValue;
            table[leaf, new BitSet(0, n)] = 1;
            table[leaf, nleaf] = 1;
            table[new BitSet(0, n), nleaf] = 0;

            for (int i = 1; i < sequence.Count; i++)
            {
                int v = sequence[i];

                left.Add(v);
                right.Remove(v);

                LinearRepresentativeList LRw = cuts[left];
                LinearRepresentativeList LRw_ = cuts[right];

                LinearRepresentativeList LRa = cuts[left - v];
                LinearRepresentativeList LRa_ = cuts[right + v];

                LookupTable newTable = new LookupTable();

                foreach (BitSet outside in LRw_)
                {
                    foreach (BitSet inside in LRa)
                    {
                        BitSet nrw_ = graph.Neighborhood(outside) * (left - v);
                        BitSet ra_ = LRa_.GetRepresentative(nrw_);

                        BitSet nra = graph.Neighborhood(inside) * right;
                        BitSet rw = LRw.GetRepresentative(nra);

                        int savedValue = newTable[rw, outside];
                        int newValue = table[inside, ra_];

                        BitSet raw_ = inside + outside;
                        BitSet nraw_ = graph.Neighborhood(raw_);
                        if (!nraw_.Contains(v))
                            newValue = int.MaxValue;

                        int min = Math.Min(savedValue, newValue);
                        newTable[rw, outside] = min;

                        //--------

                        nrw_ = graph.Neighborhood(outside + v) * (left - v);
                        ra_ = LRa_.GetRepresentative(nrw_);

                        nra = graph.Neighborhood(inside + v) * right;
                        rw = LRw.GetRepresentative(nra);

                        savedValue = newTable[rw, outside];
                        newValue = table[inside, ra_];
                        newValue = newValue == int.MaxValue ? newValue : newValue + 1;
                        min = Math.Min(savedValue, newValue);
                        newTable[rw,  outside] = min;
                    }
                }

                table = newTable;
            }

            return table[new BitSet(0, graph.Size), new BitSet(0, graph.Size)];
        }
Exemplo n.º 29
0
 public int this[BitSet inside, BitSet outside]
 {
     get
     {
         Tuple<BitSet, BitSet> t = new Tuple<BitSet, BitSet>(inside, outside);
         if (!Data.ContainsKey(t))
             return int.MaxValue;
         return Data[t];
     }
     set
     {
         Tuple<BitSet, BitSet> t = new Tuple<BitSet, BitSet>(inside, outside);
         Data[t] = value;
     }
 }
 // Indexer
 public LinearRepresentativeList this[BitSet cut]
 {
     get { return Table[cut]; }
 }