/// <summary>
/// If possible, relax the given edge using the supplied base cost and edge-weight function.
/// </summary>
/// <param name="edge">The edge to relax.</param>
/// <param name="cost">The base cost to reach the edge destination vertex.</param>
/// <param name="ew">The edge weigher.</param>
/// <param name="forbidNegatives">If true, negative values will forbid the link.</param>
/// <returns>True if the edge was relaxed, otherwise false.</returns>
public bool RelaxEdge(E edge, IWeight cost, IEdgeWeigher <V, E> ew, bool forbidNegatives = true)
{
V v = edge.Dst;
IWeight hopCost = ew.GetWeight(edge);
if ((!hopCost.IsViable) || (hopCost.IsNegative && forbidNegatives))
{
return(false);
}
IWeight newCost = cost.Merge(hopCost);
int compareResult = -1;
if (HasCost(v))
{
IWeight oldCost = GetCost(v);
compareResult = newCost.CompareTo(oldCost);
}
if (compareResult <= 0)
{
UpdateVertex(v, edge, newCost, compareResult < 0);
}
return(compareResult < 0);
}
/// <summary>
/// Sums the given edges using the given weigher.
/// </summary>
/// <param name="weigher">The weigher to use.</param>
/// <param name="edges">The edges to sum.</param>
/// <returns>The sum of path cost between the given edges.</returns>
private IWeight CalculatePathCost(IEdgeWeigher <V, E> weigher, IEnumerable <E> edges)
{
IWeight totalCost = weigher.InitialWeight;
foreach (E edge in edges)
{
totalCost = totalCost.Merge(weigher.GetWeight(edge));
}
return(totalCost);
}
