/// <summary>
/// O(n * k * logk) // much faster than O(n logn) for k << n
/// </summary>
/// <param name="s"></param>
/// <param name="p"></param>
/// <param name="conf"></param>
/// <returns></returns>
public long UpdateKnn(IAlgorithm s, IP p, KnnConfiguration conf)
{
conf = conf ?? new KnnConfiguration();
var sw = new Stopwatch();
sw.Start();
s.Knn.Clear();
s.Knn.Origin = p;
s.Knn.K = conf.K;
//var all = new List<IPDist>(); // naive version
var sortedList2 = new SortedList2(); // better naive version
var n = s.Points.Count;
for (var i = 0; i < n; i++)
{
var p1 = s.Points[i];
if (p.Equals(p1))
{
continue; // don't include origin
}
if (conf.SameTypeOnly && p.Type != p1.Type)
{
continue; // only same type used
}
var dist = p.Distance(p1.X, p1.Y);
if (dist >= conf.MaxDistance)
{
continue;
}
var pdist = new PDist {
Point = p1, Distance = dist
};
//all.Add(pdist); // naive version
sortedList2.Add(pdist, conf.K); // better naive version
}
//s.Knn.NNs = all.OrderBy(i => i.Distance).Take(conf.K).ToList(); // O(n logn)
s.Knn.NNs = sortedList2.GetAll(); // O(n * k * logk) // better naive version
sw.Stop();
return(sw.ElapsedMilliseconds);
}
public ObservableCollectionSortedIndex(string name, IObservableCollection <T> collection, string[] watchProperties, Func <T, object> keyGetter, System.Collections.IComparer comparer) : base(name, collection, watchProperties, keyGetter, comparer)
{
_items = new SortedList2(new SortedList2ItemComparer(comparer));
Initialize();
}
