public static long RunParallelForPrim(this Graph g)
{
var used = new HashSet <int>();
var unused = new HashSet <int>();
used.Add(0);
for (var i = 1; i < g.VerticesNumber; ++i)
{
unused.Add(i);
}
long result = 0;
while (unused.Count != 0)
{
var curs = new long[g.VerticesNumber];
var ends = new int[g.VerticesNumber];
Parallel.ForEach(used, v =>
{
foreach (var u in unused)
{
var cost = g.AdjacencyMatrix[v, u];
if (cost != 0 && (curs[v] == 0 || curs[v] > cost))
{
curs[v] = cost;
ends[v] = u;
}
}
});
var cur = new Graph.Edge(0, 0, long.MaxValue);
foreach (var v in used)
{
if (cur.weight > curs[v])
{
cur = new Graph.Edge(v, ends[v], curs[v]);
}
}
result += cur.weight;
unused.Remove(cur.end);
used.Add(cur.end);
}
return(result);
}
public static long RunSequentialPrim(this Graph g)
{
var used = new HashSet <int>();
var unused = new HashSet <int>();
used.Add(0);
for (var i = 1; i < g.VerticesNumber; ++i)
{
unused.Add(i);
}
long result = 0;
while (unused.Count != 0)
{
var cur = new Graph.Edge(0, 0, long.MaxValue);
foreach (var v in used)
{
foreach (var u in unused)
{
var cost = g.AdjacencyMatrix[v, u];
if (cost != 0 && cur.weight > cost)
{
cur = new Graph.Edge(v, u, cost);
}
}
}
result += cur.weight;
unused.Remove(cur.end);
used.Add(cur.end);
}
return(result);
}
public static long RunParallelThreadsPrim(this Graph g)
{
var used = new HashSet <int>();
var unused = new HashSet <int>();
used.Add(0);
for (var i = 1; i < g.VerticesNumber; ++i)
{
unused.Add(i);
}
long result = 0;
while (unused.Count != 0)
{
var curs = new long[g.VerticesNumber];
var ends = new int[g.VerticesNumber];
var isDone = new AutoResetEvent(false);
var completed = used.Count;
foreach (var v in used)
{
ThreadPool.QueueUserWorkItem(_ =>
{
foreach (var u in unused)
{
var cost = g.AdjacencyMatrix[v, u];
if (cost != 0 && (curs[v] == 0 || curs[v] > cost))
{
curs[v] = cost;
ends[v] = u;
}
}
if (Interlocked.Decrement(ref completed) == 0)
{
isDone.Set();
}
});
}
isDone.WaitOne();
var cur = new Graph.Edge(0, 0, long.MaxValue);
foreach (var v in used)
{
if (cur.weight > curs[v])
{
cur = new Graph.Edge(v, ends[v], curs[v]);
}
}
result += cur.weight;
unused.Remove(cur.end);
used.Add(cur.end);
}
return(result);
}
public static long RunParallelThreadsKruskal(this Graph g)
{
var dsu = new DisjointSetUnion(g.VerticesNumber);
var edges = new List <Graph.Edge>();
var chunkSize = g.EdgesNumber;
if (g.EdgesNumber > Environment.ProcessorCount)
{
chunkSize = g.EdgesNumber / Environment.ProcessorCount;
}
var chunksNumber = g.EdgesNumber / chunkSize;
var chunks = new List <Graph.Edge> [chunksNumber];
var tasks = new List <Task>();
var start = new int[chunksNumber];
for (int i = 0, chunk = chunkSize; i < g.EdgesNumber; i += chunk)
{
if (i + 2 * chunk > g.EdgesNumber)
{
chunk = g.EdgesNumber - i;
}
chunks[i / chunkSize] = new List <Graph.Edge>();
for (var j = i; j < i + chunk; ++j)
{
chunks[i / chunkSize].Add(g.Edges[j]);
}
var i1 = i / chunkSize;
tasks.Add(Task.Run(() => chunks[i1].Sort()));
}
Task.WaitAll(tasks.ToArray());
while (edges.Count != g.EdgesNumber)
{
var cur = new Graph.Edge();
var id = -1;
for (var i = 0; i < chunks.Length; ++i)
{
if (start[i] < chunks[i].Count && (id == -1 || chunks[i][start[i]].weight < cur.weight))
{
id = i;
cur = chunks[i][start[i]];
}
}
edges.Add(cur);
++start[id];
}
long result = 0;
foreach (var edge in edges)
{
if (dsu.Find(edge.start) != dsu.Find(edge.end))
{
result += edge.weight;
dsu.Union(edge.start, edge.end);
}
}
return(result);
}
