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);
}
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);
}
}
}
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);
}
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);
}
