Пример #1
0
        public override bool Search()
        {
            //create a std stack of edges
            Queue <NavGraphEdge> Q = new Queue <NavGraphEdge>();

            //create a dummy edge and put on the Queue
            NavGraphEdge Dummy = new NavGraphEdge(m_iSource, m_iSource, 0);

            Q.Enqueue(Dummy);

            //mark the source node as visited
            m_Visited[m_iSource] = (int)NodeState.visited;

            //while there are edges in the stack keep searching
            while (Q.Count > 0)
            {
                //grab and remove the next edge
                NavGraphEdge NextEdge = Q.Dequeue();

                //make a note of the parent of the node this edge points to
                m_Route[NextEdge.To] = NextEdge.From;

                //put it on the tree. (making sure the dummy edge is not placed on the tree)
                if (NextEdge != Dummy)
                {
                    m_SpanningTree.Add(NextEdge);
                }

                //if the target has been found the method can return success
                if (NextEdge.To == m_iTarget)
                {
                    return(true);
                }

                //push the edges leading from the node this edge points to onto
                //the queue

                SparseGraph.EdgeIterator EdgeItr = new SparseGraph.EdgeIterator(m_Graph, NextEdge.To);

                while (EdgeItr.MoveNext())
                {
                    if (m_Visited[EdgeItr.Current.To] == (int)NodeState.unvisited)
                    {
                        Q.Enqueue(EdgeItr.Current);

                        //and mark it visited
                        m_Visited[EdgeItr.Current.To] = (int)NodeState.visited;
                    }
                }
            }

            //no path to target
            return(false);
        }
Пример #2
0
        public static void Helper_WeightNavGraphNodeEdges(SparseGraph graph, int node, double weight)
        {
            //make sure the node is present
            Debug.Assert(node < graph.NumNodes(), "Node can not exist in graph!");

            //set the cost for each edge
            SparseGraph.EdgeIterator EdgeItr = new SparseGraph.EdgeIterator(graph, node);

            while (EdgeItr.MoveNext())
            {
                //calculate the distance between nodes
                double dist = Vector2D.Vec2DDistance(graph.GetNode(EdgeItr.Current.From).Pos,
                                                     graph.GetNode(EdgeItr.Current.To).Pos);

                //set the cost of this edge
                graph.SetEdgeCost(EdgeItr.Current.From, EdgeItr.Current.To, dist * weight);

                //if not a digraph, set the cost of the parallel edge to be the same
                if (!graph.isDigraph())
                {
                    graph.SetEdgeCost(EdgeItr.Current.To, EdgeItr.Current.From, dist * weight);
                }
            }
        }
Пример #3
0
        public override bool Search()
        {
            //create an indexed priority queue that sorts smallest to largest
            //(front to back).Note that the maximum number of elements the iPQ
            //may contain is N. This is because no node can be represented on the
            //queue more than once.
            IndexedPriorityQLow pq = new IndexedPriorityQLow(m_FCosts, m_Graph.NumNodes());

            //put the source node on the queue
            pq.insert(m_iSource);

            //while the queue is not empty
            while (!pq.empty())
            {
                //get lowest cost node from the queue.
                int NextClosestNode = pq.Pop();

                //move this node from the frontier to the spanning tree
                m_ShortestPathTree[NextClosestNode] = m_SearchFrontier[NextClosestNode];

                //if the target has been found exit
                if (NextClosestNode == m_iTarget)
                {
                    return(true);
                }

                //now to relax the edges.
                SparseGraph.EdgeIterator EdgeItr = new SparseGraph.EdgeIterator(m_Graph, NextClosestNode);

                while (EdgeItr.MoveNext())
                {
                    //calculate the heuristic cost from this node to the target (H)
                    double HCost = funcPointer(m_Graph, m_iTarget, EdgeItr.Current.To);

                    //calculate the 'real' cost to this node from the source (G)
                    double GCost = m_GCosts[NextClosestNode] + EdgeItr.Current.Cost;

                    //if the node has not been added to the frontier, add it and update
                    //the G and F costs
                    if (NavGraphEdge.IsNull(m_SearchFrontier[EdgeItr.Current.To]))
                    {
                        m_FCosts[EdgeItr.Current.To] = GCost + HCost;
                        m_GCosts[EdgeItr.Current.To] = GCost;

                        pq.insert(EdgeItr.Current.To);

                        m_SearchFrontier[EdgeItr.Current.To] = EdgeItr.Current;
                    }
                    //if this node is already on the frontier but the cost to get here
                    //is cheaper than has been found previously, update the node
                    //costs and frontier accordingly.
                    else if ((GCost < m_GCosts[EdgeItr.Current.To]) && NavGraphEdge.IsNull(m_ShortestPathTree[EdgeItr.Current.To]))
                    {
                        m_FCosts[EdgeItr.Current.To] = GCost + HCost;
                        m_GCosts[EdgeItr.Current.To] = GCost;

                        pq.ChangePriority(EdgeItr.Current.To);

                        m_SearchFrontier[EdgeItr.Current.To] = EdgeItr.Current;
                    }
                }
            }
            return(false);
        }
Пример #4
0
        public override bool Search()
        {
            //create an indexed priority queue that sorts smallest to largest
            //(front to back).Note that the maximum number of elements the iPQ
            //may contain is N. This is because no node can be represented on the
            //queue more than once.
            IndexedPriorityQLow pq = new IndexedPriorityQLow(m_CostToThisNode, m_Graph.NumNodes());

            //put the source node on the queue
            pq.insert(m_iSource);

            //while the queue is not empty
            while (!pq.empty())
            {
                //get lowest cost node from the queue. Don't forget, the return value
                //is a *node index*, not the node itself. This node is the node not already
                //on the SPT that is the closest to the source node
                int NextClosestNode = pq.Pop();

                //move this edge from the frontier to the shortest path tree
                m_ShortestPathTree[NextClosestNode] = m_SearchFrontier[NextClosestNode];

                //if the target has been found exit
                if (NextClosestNode == m_iTarget)
                {
                    return(true);
                }

                //now to relax the edges.
                SparseGraph.EdgeIterator EdgeItr = new SparseGraph.EdgeIterator(m_Graph, NextClosestNode);

                while (EdgeItr.MoveNext())
                {
                    //the total cost to the node this edge points to is the cost to the
                    //current node plus the cost of the edge connecting them.
                    double NewCost = m_CostToThisNode[NextClosestNode] + EdgeItr.Current.Cost;

                    //if this edge has never been on the frontier make a note of the cost
                    //to get to the node it points to, then add the edge to the frontier
                    //and the destination node to the PQ.
                    if (NavGraphEdge.IsNull(m_SearchFrontier[EdgeItr.Current.To]))
                    {
                        m_CostToThisNode[EdgeItr.Current.To] = NewCost;

                        pq.insert(EdgeItr.Current.To);

                        m_SearchFrontier[EdgeItr.Current.To] = EdgeItr.Current;
                    }

                    //else test to see if the cost to reach the destination node via the
                    //current node is cheaper than the cheapest cost found so far. If
                    //this path is cheaper, we assign the new cost to the destination
                    //node, update its entry in the PQ to reflect the change and add the
                    //edge to the frontier
                    else if ((NewCost < m_CostToThisNode[EdgeItr.Current.To]) &&
                             NavGraphEdge.IsNull(m_ShortestPathTree[EdgeItr.Current.To]))
                    {
                        m_CostToThisNode[EdgeItr.Current.To] = NewCost;

                        //because the cost is less than it was previously, the PQ must be
                        //re-sorted to account for this.
                        pq.ChangePriority(EdgeItr.Current.To);

                        m_SearchFrontier[EdgeItr.Current.To] = EdgeItr.Current;
                    }
                }
            }
            return(false);
        }