private static void Sort <T>(T[] collection, int maxDegreeOfParallelism, IComparer <T> comparer, [NotNull] SortState state)
{
const int sequentialThreshold = 2048;
// Other threads already processed all work before this one started. ActiveWorkerCount is already 0
if (state.Partitions.IsEmpty)
{
state.Release();
return;
}
// This thread is now actively processing work items, meaning there might be work in progress
Interlocked.Increment(ref state.ActiveWorkerCount);
var hasChild = false;
try
{
SortRange range;
while (state.Partitions.TryDequeue(out range))
{
if (range.Right - range.Left < sequentialThreshold)
{
// Sort small collections sequentially
Array.Sort(collection, range.Left, range.Right - range.Left + 1, comparer);
}
else
{
var pivot = Partition(collection, range.Left, range.Right, comparer);
// Add work items
if (pivot - 1 > range.Left)
{
state.Partitions.Enqueue(new SortRange(range.Left, pivot - 1));
}
if (range.Right > pivot + 1)
{
state.Partitions.Enqueue(new SortRange(pivot + 1, range.Right));
}
// Add a new worker if necessary
if (maxDegreeOfParallelism > 1 && !hasChild)
{
state.AddReference();
Fork(collection, maxDegreeOfParallelism, comparer, state);
hasChild = true;
}
}
}
}
finally
{
state.Release();
if (Interlocked.Decrement(ref state.ActiveWorkerCount) == 0)
{
state.Finished.Set();
}
}
}
private static void SortOnThread <T>(T[] collection, IComparer <T> comparer, [NotNull] SortState state)
{
const int sequentialThreshold = 2048;
var hasChild = false;
try
{
var sw = new SpinWait();
while (Volatile.Read(ref state.OpLeft) != 0)
{
if (state.Partitions.TryDequeue(out var range) == false)
{
sw.SpinOnce();
continue;
}
if (range.Right - range.Left < sequentialThreshold)
{
// Sort small collections sequentially
Array.Sort(collection, range.Left, range.Right - range.Left + 1, comparer);
Interlocked.Decrement(ref state.OpLeft);
}
else
{
var pivot = Partition(collection, range.Left, range.Right, comparer);
int delta = -1;
// Add work items
if (pivot - 1 > range.Left)
{
delta++;
}
if (range.Right > pivot + 1)
{
delta++;
}
Interlocked.Add(ref state.OpLeft, delta);
if (pivot - 1 > range.Left)
{
state.Partitions.Enqueue(new SortRange(range.Left, pivot - 1));
}
if (range.Right > pivot + 1)
{
state.Partitions.Enqueue(new SortRange(pivot + 1, range.Right));
}
// Add a new worker if necessary
if (!hasChild)
{
var w = Interlocked.Decrement(ref state.MaxWorkerCount);
if (w >= 0)
{
state.AddReference();
ThreadPool.Instance.QueueWorkItem(() => SortOnThread(collection, comparer, state));
}
hasChild = true;
}
}
}
}
finally
{
if (Volatile.Read(ref state.OpLeft) == 0)
{
state.Finished.Set();
}
state.Release();
}
}