public override void Compute(CancellationToken cancellationToken)
{
if (VisitedGraph.VertexCount == 1)
{
VertexPositions.Add(VisitedGraph.Vertices.First(), new Point(0, 0));
return;
}
#region Initialization
_distances = new double[VisitedGraph.VertexCount, VisitedGraph.VertexCount];
_edgeLengths = new double[VisitedGraph.VertexCount, VisitedGraph.VertexCount];
_springConstants = new double[VisitedGraph.VertexCount, VisitedGraph.VertexCount];
_vertices = new TVertex[VisitedGraph.VertexCount];
_positions = new Point[VisitedGraph.VertexCount];
//initializing with random positions
InitializeWithRandomPositions(Parameters.Width, Parameters.Height);
//copy positions into array (speed-up)
int index = 0;
foreach (var v in VisitedGraph.Vertices)
{
_vertices[index] = v;
_positions[index] = VertexPositions[v];
index++;
}
//calculating the diameter of the graph
//TODO check the diameter algorithm
_diameter = VisitedGraph.GetDiameter <TVertex, TEdge, TGraph>(out _distances);
//L0 is the length of a side of the display area
double l0 = Math.Min(Parameters.Width, Parameters.Height);
//ideal length = L0 / max d_i,j
_idealEdgeLength = (l0 / _diameter) * Parameters.LengthFactor;
//calculating the ideal distance between the nodes
for (int i = 0; i < VisitedGraph.VertexCount - 1; i++)
{
cancellationToken.ThrowIfCancellationRequested();
for (int j = i + 1; j < VisitedGraph.VertexCount; j++)
{
cancellationToken.ThrowIfCancellationRequested();
//distance between non-adjacent vertices
double dist = _diameter * Parameters.DisconnectedMultiplier;
//calculating the minimal distance between the vertices
if (_distances[i, j] != double.MaxValue)
{
dist = Math.Min(_distances[i, j], dist);
}
if (_distances[j, i] != double.MaxValue)
{
dist = Math.Min(_distances[j, i], dist);
}
_distances[i, j] = _distances[j, i] = dist;
_edgeLengths[i, j] = _edgeLengths[j, i] = _idealEdgeLength * dist;
_springConstants[i, j] = _springConstants[j, i] = Parameters.K / Math.Pow(dist, 2);
}
}
#endregion
int n = VisitedGraph.VertexCount;
if (n == 0)
{
return;
}
//TODO check this condition
for (int currentIteration = 0; currentIteration < Parameters.MaxIterations; currentIteration++)
{
cancellationToken.ThrowIfCancellationRequested();
#region An iteration
double maxDeltaM = double.NegativeInfinity;
int pm = -1;
//get the 'p' with the max delta_m
for (int i = 0; i < n; i++)
{
cancellationToken.ThrowIfCancellationRequested();
double deltaM = CalculateEnergyGradient(i);
if (maxDeltaM < deltaM)
{
maxDeltaM = deltaM;
pm = i;
}
}
//TODO is needed?
if (pm == -1)
{
return;
}
//calculating the delta_x & delta_y with the Newton-Raphson method
//there is an upper-bound for the while (deltaM > epsilon) {...} cycle (100)
for (int i = 0; i < 100; i++)
{
_positions[pm] += CalcDeltaXY(pm);
double deltaM = CalculateEnergyGradient(pm);
//real stop condition
if (deltaM < double.Epsilon)
{
break;
}
}
//what if some of the vertices would be exchanged?
if (Parameters.ExchangeVertices && maxDeltaM < double.Epsilon)
{
double energy = CalcEnergy();
for (int i = 0; i < n - 1; i++)
{
cancellationToken.ThrowIfCancellationRequested();
for (int j = i + 1; j < n; j++)
{
cancellationToken.ThrowIfCancellationRequested();
double xenergy = CalcEnergyIfExchanged(i, j);
if (energy > xenergy)
{
Point p = _positions[i];
_positions[i] = _positions[j];
_positions[j] = p;
return;
}
}
}
}
#endregion
/* if ( ReportOnIterationEndNeeded )
* Report( currentIteration );*/
}
Report(Parameters.MaxIterations);
}
