详解c# PLINQ中的分区

//
// An orderable dynamic partitioner for lists
//
class OrderableListPartitioner<TSource> : OrderablePartitioner<TSource>
{
  private readonly IList<TSource> m_input;

  public OrderableListPartitioner(IList<TSource> input)
    : base(true, false, true)
  {
    m_input = input;
  }

  // Must override to return true.
  public override bool SupportsDynamicPartitions
  {
    get
    {
      return true;
    }
  }

  public override IList<IEnumerator<KeyValuePair<long, TSource>>>
    GetOrderablePartitions(int partitionCount)
  {
    var dynamicPartitions = GetOrderableDynamicPartitions();
    var partitions =
      new IEnumerator<KeyValuePair<long, TSource>>[partitionCount];

    for (int i = 0; i < partitionCount; i++)
    {
      partitions[i] = dynamicPartitions.GetEnumerator();
    }
    return partitions;
  }

  public override IEnumerable<KeyValuePair<long, TSource>>
    GetOrderableDynamicPartitions()
  {
    return new ListDynamicPartitions(m_input);
  }

  private class ListDynamicPartitions
    : IEnumerable<KeyValuePair<long, TSource>>
  {
    private IList<TSource> m_input;
    private int m_pos = 0;

    internal ListDynamicPartitions(IList<TSource> input)
    {
      m_input = input;
    }

    public IEnumerator<KeyValuePair<long, TSource>> GetEnumerator()
    {
      while (true)
      {
        // Each task gets the next item in the list. The index is
        // incremented in a thread-safe manner to avoid races.
        int elemIndex = Interlocked.Increment(ref m_pos) - 1;

        if (elemIndex >= m_input.Count)
        {
          yield break;
        }

        yield return new KeyValuePair<long, TSource>(
          elemIndex, m_input[elemIndex]);
      }
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
      return
        ((IEnumerable<KeyValuePair<long, TSource>>)this)
        .GetEnumerator();
    }
  }
}

class ConsumerClass
{
  static void Main()
  {
    var nums = Enumerable.Range(0, 10000).ToArray();
    OrderableListPartitioner<int> partitioner = new OrderableListPartitioner<int>(nums);

    // Use with Parallel.ForEach
    Parallel.ForEach(partitioner, (i) => Console.WriteLine(i));


    // Use with PLINQ
    var query = from num in partitioner.AsParallel()
          where num % 2 == 0
          select num;

    foreach (var v in query)
      Console.WriteLine(v);
  }
}