/// <summary>
/// Initializes the P array for the algorithm.
/// </summary>
/// <param name="startingNode">
/// The node that has been designated the starting node for the entire algorithm.
/// </param>
/// <returns>
/// The new P array.
/// </returns>
/// <remarks>
/// A fresh P array will set every single node's source node to be
/// the starting node, including the starting node itself.
/// </remarks>
protected virtual int[] GetStartingBestPath(int startingNode, DijkstraInfo di)
{
int[] p = new int[TotalNodeCount];
for (int i = 0; i < p.Length; i++)
{
p[i] = startingNode;
}
return(p);
}
/// <summary>
/// Initializes the D array for the start of the algorithm.
/// </summary>
/// <param name="start">
/// The starting node.
/// </param>
/// <returns>
/// The contents of the new D array.
/// </returns>
/// <remarks>
/// The traversal cost for every node will be set to impossible
/// (int.MaxValue) unless a connecting edge is found between the
/// <paramref name="start"/>ing node and the node in question.
/// </remarks>
protected virtual int[] GetStartingTraversalCost(int start, DijkstraInfo di)
{
int[] subset = new int[TotalNodeCount];
for (int i = 0; i < subset.Length; i++)
{
subset[i] = int.MaxValue; // all are unreachable
}
subset[start] = 0; // zero cost from start to start
foreach (int nearby in Hint(start, di))
{
subset[nearby] = TraversalCost(start, nearby, di);
}
return(subset);
}
private int getInternodeTraversalCost(int start, int finish, DijkstraInfo di)
{
//TODO: If Dijkstra gets slow
//This is sloppy:
//(1) It loops through all edges/arrows: could have pointers in the nodes themselves ('parents' and 'children')
// Then we could check the start node and see if it points to finish node. (Or make a hashtable of connections)
//See also nearbyNodesHint()
foreach (EdgeData ed in di.edges)
{
if (ed.to == start && ed.from == finish)
{
return(1);
}
}
return(int.MaxValue);
}
/// <summary>
/// Performs the Dijkstra algorithm on the data provided when the
/// <see cref="Dijkstra"/> object was instantiated.
/// </summary>
/// <param name="start">
/// The node to use as a starting location.
/// </param>
/// <returns>
/// A struct containing both the minimum distance and minimum path
/// to every node from the given <paramref name="start"/> node.
/// </returns>
public virtual Results Perform(int start, DijkstraInfo di)
{
// Initialize the distance to every node from the starting node.
int[] d = GetStartingTraversalCost(start, di);
// Initialize best path to every node as from the starting node.
int[] p = GetStartingBestPath(start, di);
ICollection <int> c = GetChoices();
c.Remove(start); // take starting node out of the list of choices
//Debug.WriteLine("Step v C D P");
//Debug.WriteLine(string.Format("init - {{{0}}} [{1}] [{2}]",
// ArrayToString<int>(",", c), ArrayToString<int>(",", d), ArrayToString<int>(",", p)));
//int step = 0;
// begin greedy loop
while (c.Count > 1)
{
// Find element v in c, that minimizes d[v]
int v = FindMinimizingDinC(d, c);
c.Remove(v); // remove v from the list of future solutions
// Consider all unselected nodes and consider their cost from v.
foreach (int w in (Hint != null ? Hint(v, di) : c))
{
if (!c.Contains(w))
{
continue; // discard pixels not in c
}
// At this point, relative(Index) points to a candidate pixel,
// that has not yet been selected, and lies within our area of interest.
// Consider whether it is now within closer reach.
int cost = TraversalCost(v, w, di);
if (cost < int.MaxValue && d[v] + cost < d[w]) // don't let wrap-around negatives slip by
{
// We have found a better way to get at relative
d[w] = d[v] + cost; // record new distance
// Record how we came to this new pixel
p[w] = v;
}
}
//Debug.WriteLine(string.Format("{4} {3} {{{0}}} [{1}] [{2}]",
// ArrayToString<int>(",", c), ArrayToString<int>(",", d), ArrayToString<int>(",", p), v + 1, ++step));
}
return(new Results(p, d));
}
private IEnumerable <int> nearbyNodesHint(int startingNode, DijkstraInfo di)
{
//TODO: If Dijkstra gets slow
//This is sloppy in two ways:
//(1) It loops through all edges/arrows: could have pointers in the nodes themselves ('parents' and 'children')
//(2) It creates a new List<int>. If the above is done, we could just point to the 'children' list.
//See also getInternodeTraversalCost()
List <int> nearbyNodes = new List <int>();
foreach (EdgeData ed in di.edges)
{
if (ed.to == startingNode)
{
nearbyNodes.Add(ed.from); //there should be no dublets in this list
}
}
return(nearbyNodes);
}
public DataModel(int iterations, double weightMax, bool firstTime)
{
if (FruchtermanReingoldLayout.h == null)
{
return;
}
//
// Populate the data model with some example data.
//
if (firstTime || FlowGlobals.rectangles == null)
{
FlowGlobals.rectangles = new ObservableCollection <RectangleData>();
FlowGlobals.arrows = new ObservableCollection <ArrowData>();
}
else
{
FlowGlobals.rectangles.Clear();
FlowGlobals.arrows.Clear();
}
ObservableCollection <RectangleData> rectangles = FlowGlobals.rectangles;
ObservableCollection <ArrowData> arrows = FlowGlobals.arrows;
double width = 90;
double height = 70;
Random r = new Random(12345);
r = new Random(54321);
r = new Random(11111);
List <EdgeData> edges = new List <EdgeData>();
List <NodeData> nodes = new List <NodeData>();
NodeData startNode = null;
foreach (FlowArrow fa in FruchtermanReingoldLayout.h.flowArrows)
{
if (!double.IsNaN(weightMax) && Math.Abs(fa.weight) < weightMax)
{
continue;
}
EdgeData ed = new EdgeData {
from = fa.counter1, to = fa.counter2, weight = fa.weight
};
edges.Add(ed);
}
foreach (FlowNode fa in FruchtermanReingoldLayout.h.flowNodes)
{
NodeData nd = new NodeData {
x = r.Next((int)(0.005d * contentWidth), (int)contentWidth), y = r.Next((int)(0.005d * contentWidth), (int)contentWidth), name = fa.varName, labelBig = fa.labelBig, isExogenous = fa.isExogenous, isStartNode = fa.isStartNode, id = fa.id
};
nodes.Add(nd);
if (nd.isStartNode)
{
startNode = nd;
}
}
Dictionary <int, NodeData> d = new Dictionary <int, NodeData>();
foreach (NodeData nd in nodes)
{
d.Add(nd.id, nd);
}
//TODO: The Dijkstra algorithm is a bit sloppy, for instance using List<int> and removing items from this list (use Dictionary instead)
DijkstraInfo di = new DijkstraInfo();
di.nodes = nodes;
di.edges = edges;
Dijkstra dijkstra = new Dijkstra(nodes.Count, new Dijkstra.InternodeTraversalCost(getInternodeTraversalCost), new Dijkstra.NearbyNodesHint(nearbyNodesHint), di);
Dijkstra.Results results = dijkstra.Perform(startNode.id, di);
//int[] minimumPath = dijkstra.GetMinimumPath(0, 102, di);
//Now we filter out
List <EdgeData> edges2 = new List <EdgeData>();
List <NodeData> nodes2 = new List <NodeData>();
int large = 1000000000;
Dictionary <int, int> rename = new Dictionary <int, int>();
foreach (NodeData nd in nodes)
{
int value = results.MinimumDistance[nd.id];
if (value < 0)
{
value = large; //do not minus it: -int.MinValue gives a strange result!
}
if (value < large) //it seems these distances can become = int.MinValue, maybe int.MaxValue+1. So this is to identify those.
{
int number = nodes2.Count;
rename.Add(nd.id, number);
nd.id = number; //now id numbers in List 'nodes' are inconsistent, but never mind that
nodes2.Add(nd);
}
}
foreach (EdgeData ed in edges)
{
if (rename.ContainsKey(ed.from) && rename.ContainsKey(ed.to))
{
ed.from = rename[ed.from];
ed.to = rename[ed.to];
edges2.Add(ed); //now id numbers in List 'edges' are inconsistent, but never mind that
}
}
SolveInfo si = new SolveInfo();
si.width = width;
si.height = height;
si.rectangles = rectangles;
si.arrows = arrows;
si.edges = edges2;
si.nodes = nodes2;
si.iterations = iterations;
if (si.iterations == -12345)
{
si.iterations = 200;
}
si.useSmartRepulse = true;
si.useWeight = true;
FruchtermanReingoldLayout.Solve(si);
}
/// <summary>
/// Creates an instance of the <see cref="Dijkstra"/> class.
/// </summary>
/// <param name="totalNodeCount">
/// The total number of nodes in the graph.
/// </param>
/// <param name="traversalCost">
/// The delegate that can provide the cost of a transition between
/// any two nodes.
/// </param>
/// <param name="hint">
/// An optional delegate that can provide a small subset of nodes
/// that a given node may be connected to.
/// </param>
public Dijkstra(int totalNodeCount, InternodeTraversalCost traversalCost, NearbyNodesHint hint, DijkstraInfo di)
{
if (totalNodeCount < 3)
{
throw new ArgumentOutOfRangeException("totalNodeCount", totalNodeCount, "Expected a minimum of 3.");
}
if (traversalCost == null)
{
throw new ArgumentNullException("traversalCost");
}
Hint = hint;
TraversalCost = traversalCost;
TotalNodeCount = totalNodeCount;
}
/// <summary>
/// Finds an array of nodes that provide the shortest path
/// from one given node to another.
/// </summary>
/// <param name="start">
/// The starting node.
/// </param>
/// <param name="finish">
/// The finishing node.
/// </param>
/// <param name="shortestPath">
/// The P array of the completed algorithm.
/// </param>
/// <returns>
/// The list of nodes that provide the one step at a time path
/// from <paramref name="start"/> to <paramref name="finish"/> nodes.
/// </returns>
protected virtual int[] GetMinimumPath(int start, int finish, int[] shortestPath, DijkstraInfo di)
{
Stack <int> path = new Stack <int>();
do
{
path.Push(finish);
finish = shortestPath[finish]; // step back one step toward the start point
}while (finish != start);
return(path.ToArray());
}
/// <summary>
/// Uses the Dijkstra algorithhm to find the minimum path
/// from one node to another.
/// </summary>
/// <param name="start">
/// The node to use as a starting location.
/// </param>
/// <param name="finish">
/// The node to use as a finishing location.
/// </param>
/// <returns>
/// A struct containing both the minimum distance and minimum path
/// to every node from the given <paramref name="start"/> node.
/// </returns>
public virtual int[] GetMinimumPath(int start, int finish, DijkstraInfo di)
{
Results results = Perform(start, di);
return(GetMinimumPath(start, finish, results.MinimumPath, di));
}