使C#ParallelEnumerable.OrderBy稳定排序 [英] Make C# ParallelEnumerable.OrderBy stable sort

问题描述

我正在使用OrderBy通过对象的整数ID并行排序对象列表.我有几个具有相同ID的对象，需要排序稳定.

I'm sorting a list of objects by their integer ids in parallel using OrderBy. I have a few objects with the same id and need the sort to be stable.

根据 Microsoft的文档，并行化的OrderBy不是稳定，但是有一种实现方法可以使其稳定.但是，我找不到这样的例子.

According to Microsoft's documentation, the parallelized OrderBy is not stable, but there is an implementation approach to make it stable. However, I cannot find an example of this.

var list = new List<pair>() { new pair("a", 1), new pair("b", 1), new pair("c", 2), new pair("d", 3), new pair("e", 4) };
var newList = list.AsParallel().WithDegreeOfParallelism(4).OrderBy<pair, int>(p => p.order);

private class pair {
  private String name;
  public int order;

  public pair (String name, int order) {
    this.name = name;
    this.order = order;
  }
}

推荐答案

另一种OrderBy方法提出了这种方法:

The remarks for the other OrderBy method suggest this approach:

var newList = list
   .Select((pair, index) => new { pair, index })
   .AsParallel().WithDegreeOfParallelism(4)
   .OrderBy(p => p.pair.order)
   .ThenBy(p => p.index)
   .Select(p => p.pair);

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