/// <summary>
/// Uses Kruskal's algorithm to build an MST spanning the mstNodes
/// with the given edges as a list ordered by priority ascending.
/// The edges don't need to contain only nodes given to this instance
/// via constructor.
/// O(|edges|) runtime.
/// </summary>
/// <param name="ordererdEdges">Edges ordered by priority ascending.</param>
/// <remarks>
/// Both Span methods have quadratic runtime in the graph nodes. This one
/// has a lower constant factor but needs to filter out unneeded edges (quadratic
/// in all nodes), the other one doesn't need to do any filtering (quadratic in
/// considered nodes) so if the mst nodes are generally only a very small
/// portion of all nodes, use the other Span method, if not, use this one.
/// </remarks>
public void Span(IEnumerable <DirectedGraphEdge> ordererdEdges)
{
var mstEdges = new List <DirectedGraphEdge>(_mstNodes.Count);
var set = new DisjointSet(_distances.CacheSize);
var considered = new bool[_distances.CacheSize];
var toAddCount = _mstNodes.Count - 1;
foreach (var t in _mstNodes)
{
considered[t] = true;
}
foreach (var current in ordererdEdges)
{
var inside = current.Inside;
var outside = current.Outside;
// This condition is by far the bottleneck of the method.
// (most likely because branch prediction can't predict the result)
if (!considered[inside] | !considered[outside])
{
continue;
}
if (set.Find(inside) == set.Find(outside))
{
continue;
}
mstEdges.Add(current);
set.Union(inside, outside);
if (--toAddCount == 0)
{
break;
}
}
SpanningEdges = mstEdges;
}
/// <summary>
/// Uses Kruskal's algorithm to build an MST spanning the mstNodes
/// with the given edges as a linked list ordered by priority ascending.
/// The edges don't need to contain only nodes given to this instance
/// via constructor.
/// O(|edges|) runtime.
/// </summary>
/// <param name="first">First edge of the linked list.</param>
/// <remarks>
/// Both Span methods have quadratic runtime in the graph nodes. This one
/// has a lower constant factor but needs to filter out unneeded edges (quadratic
/// in all nodes), the other one doesn't need to do any filtering (quadratic in
/// considered nodes) so if the mst nodes are generally only a very small
/// portion of all nodes, use the other Span method, if not, use this one.
/// </remarks>
public void Span(LinkedGraphEdge first)
{
var mstEdges = new List <GraphEdge>(_mstNodes.Count);
var set = new DisjointSet(_distances.CacheSize);
var considered = new bool[_distances.CacheSize];
var toAddCount = _mstNodes.Count - 1;
foreach (var t in _mstNodes)
{
considered[t.DistancesIndex] = true;
}
for (var current = first; current != null; current = current.Next)
{
var inside = current.Inside;
var outside = current.Outside;
// This condition is by far the bottleneck of the method.
// (most likely because branch prediction can't predict the result)
if (!considered[inside] | !considered[outside])
{
continue;
}
if (set.Find(inside) == set.Find(outside))
{
continue;
}
mstEdges.Add(new GraphEdge(_distances.IndexToNode(inside), _distances.IndexToNode(outside)));
set.Union(inside, outside);
if (--toAddCount == 0)
{
break;
}
}
SpanningEdges = mstEdges;
IsSpanned = true;
}
/// <summary>
/// Uses Kruskal's algorithm to build an MST spanning the mstNodes
/// with the given edges as a list ordered by priority ascending.
/// The edges don't need to contain only nodes given to this instance
/// via constructor.
/// O(|edges|) runtime.
/// </summary>
/// <param name="ordererdEdges">Edges ordered by priority ascending.</param>
/// <remarks>
/// Both Span methods have quadratic runtime in the graph nodes. This one
/// has a lower constant factor but needs to filter out unneeded edges (quadratic
/// in all nodes), the other one doesn't need to do any filtering (quadratic in
/// considered nodes) so if the mst nodes are generally only a very small
/// portion of all nodes, use the other Span method, if not, use this one.
/// </remarks>
public void Span(IEnumerable<DirectedGraphEdge> ordererdEdges)
{
var mstEdges = new List<DirectedGraphEdge>(_mstNodes.Count);
var set = new DisjointSet(_distances.CacheSize);
var considered = new bool[_distances.CacheSize];
var toAddCount = _mstNodes.Count - 1;
foreach (var t in _mstNodes)
{
considered[t] = true;
}
foreach (var current in ordererdEdges)
{
var inside = current.Inside;
var outside = current.Outside;
// This condition is by far the bottleneck of the method.
// (most likely because branch prediction can't predict the result)
if (!considered[inside] | !considered[outside]) continue;
if (set.Find(inside) == set.Find(outside)) continue;
mstEdges.Add(current);
set.Union(inside, outside);
if (--toAddCount == 0) break;
}
SpanningEdges = mstEdges;
}