private void Relax(WeightedDiGraph <T> G, T v)
{
foreach (var e in G.Adj(v))
{
T w = e.To();
if (distTo[w] > distTo[v] + e.Weight)
{
distTo[w] = distTo[v] + e.Weight;
edgeTo[w] = e;
if (!onQueue[w])
{
queue.Enqueue(w);
onQueue[w] = true;
}
}
if (cost++ % G.V() == 0)
{
FindNegativeCycle();
if (HasNegativeCycle())
{
return; // found a negative cycle
}
}
}
}
public void PriceUpdate(PriceUpdate update)
{
lock (lockTheEntireGraph)
{
var from = new ExchangeCurrency(update.Exchange, update.SourceCurrency);
var to = new ExchangeCurrency(update.Exchange, update.DestinationCurrency);
double weight = -Math.Log(update.Factor);
var oldEdge = graph.Adj(from).Where(e => e.To().CompareTo(to) == 0).SingleOrDefault();
var newEdge = new Edge <ExchangeCurrency>(from, to, weight, update.Timestamp);
if (oldEdge != null && oldEdge.TimeStamp < update.Timestamp)
{
graph.RemoveEdge(oldEdge);
graph.AddEdge(newEdge);
}
else if (oldEdge == null) // add 1<-->1 edges by currency
{
graph.AddEdge(newEdge);
foreach (var v in graph.Vertexes()
.Where(v => v.Currency == update.SourceCurrency)
.Where(v => v.CompareTo(from) != 0))
{
if (!graph.HasEdgeBetween(v, from))
{
graph.AddEdge(new Edge <ExchangeCurrency>(v, from, -Math.Log(1)));
}
if (!graph.HasEdgeBetween(from, v))
{
graph.AddEdge(new Edge <ExchangeCurrency>(from, v, -Math.Log(1)));
}
}
foreach (var v in graph.Vertexes()
.Where(v => v.Currency == update.DestinationCurrency)
.Where(v => v.CompareTo(to) != 0))
{
if (!graph.HasEdgeBetween(v, to))
{
graph.AddEdge(new Edge <ExchangeCurrency>(v, to, -Math.Log(1)));
}
if (!graph.HasEdgeBetween(to, v))
{
graph.AddEdge(new Edge <ExchangeCurrency>(to, v, -Math.Log(1)));
}
}
}
}
}
private void Dfs(WeightedDiGraph <T> G, T v)
{
onStack[v] = true;
marked[v] = true;
foreach (var e in G.Adj(v))
{
T w = e.To();
if (!marked.ContainsKey(w))
{
marked.Add(w, false); // fix to dictionary exception
}
if (cycle != null)
{
return; // if directed cycle found
}
else if (!marked[w])
{
edgeTo[w] = e;
Dfs(G, w);
}
else if (onStack[w])
{
cycle = new StackLinkedList <Edge <T> >();
Edge <T> f = e;
while (f.From().CompareTo(w) != 0)
{
cycle.Push(f);
f = edgeTo[f.From()];
}
cycle.Push(f);
return;
}
}
onStack[v] = false;
}
