AStar/astar/Astar.cs
2022-05-11 20:25:13 +02:00

107 lines
3.8 KiB
C#

using Logging;
using Graph;
namespace astar
{
public class Astar
{
/*
* Loads the graph, chooses two nodes at random and calls a*
*/
public Astar(Dictionary<UInt64, Node> nodes, Logger ?logger = null)
{
Random r = new();
List<Node> path = new();
while(path.Count < 1)
{
Node n1 = nodes[nodes.Keys.ElementAt(r.Next(0, nodes.Count - 1))];
Node n2 = nodes[nodes.Keys.ElementAt(r.Next(0, nodes.Count - 1))];
logger?.Log(LogLevel.INFO, "From {0} - {1} to {2} - {3}", n1.lat, n1.lon, n2.lat, n2.lon);
path = FindPath(ref nodes, n1, n2, ref logger);
}
logger?.Log(LogLevel.INFO, "Path found");
foreach (Node n in path)
logger?.Log(LogLevel.INFO, "lat {0:000.00000} lon {1:000.00000} traveled {2:0000.00} / {3:0000.00} beeline {4:0000.00}", n.lat, n.lon, n.pathLength, path.ElementAt(path.Count-1).pathLength, n.goalDistance);
}
/*
* Resets the calculated previous nodes and distance to goal
*/
private static void Reset(ref Dictionary<ulong, Node> nodes)
{
foreach(Node n in nodes.Values)
{
n.previousNode = Node.nullnode;
n.goalDistance = double.MaxValue;
}
}
/*
*
*/
private static List<Node> FindPath(ref Dictionary<ulong, Node> nodes, Node start, Node goal, ref Logger ?logger)
{
Reset(ref nodes);
List<Node> toVisit = new();
toVisit.Add(start);
Node currentNode = start;
start.pathLength = 0;
start.goalDistance = Utils.DistanceBetweenNodes(start, goal);
while(currentNode != goal && toVisit.Count > 0)
{
currentNode = toVisit.First();
logger?.Log(LogLevel.VERBOSE, "toVisit-length: {0} path: {1} goal: {2}", toVisit.Count, currentNode.pathLength, currentNode.goalDistance);
//Check all neighbors of current node
foreach (Edge e in currentNode.edges)
{
if (e.neighbor.goalDistance == double.MaxValue)
e.neighbor.goalDistance = Utils.DistanceBetweenNodes(e.neighbor, goal);
if (e.neighbor.pathLength > currentNode.pathLength + e.weight)
{
e.neighbor.pathLength = currentNode.pathLength + e.weight;
e.neighbor.previousNode = currentNode;
toVisit.Add(e.neighbor);
}
}
toVisit.Remove(currentNode); //"Mark" as visited
toVisit.Sort(CompareDistanceToGoal);
}
List<Node> path = new();
if (currentNode != goal)
{
logger?.Log(LogLevel.INFO, "No path between {0} - {1} and {2} - {3}", start.lat, start.lon, goal.lat, goal.lon);
return path;
}
path.Add(goal);
while(currentNode != start)
{
path.Add(currentNode.previousNode);
currentNode = currentNode.previousNode;
}
path.Reverse();
return path;
}
/*
* Compares two nodes and returns the node closer to the goal
*/
private static int CompareDistanceToGoal(Node n1, Node n2)
{
if (n1 == null || n2 == null)
return 0;
else
{
if (n1.goalDistance < n2.goalDistance)
return 1;
else if (n1.goalDistance > n2.goalDistance)
return -1;
else return 0;
}
}
}
}