如何更新存在于另一个ConcurrentDictionary中的ConcurrentDictionary？

Question

我有一个用Pr_Matrix命名的ConcurrentDictionary：

ConcurrentDictionary<int, ConcurrentDictionary<int, float>> Pr_Matrix = new ConcurrentDictionary<int, ConcurrentDictionary<int, float>>();

以下代码的目的是将data_set.Set_of_Point数据集中每对点之间的相似度值添加到此字典中。

foreach (var point_1 in data_set.Set_of_Point)
{
   foreach (var point_2 in data_set.Set_of_Point)
   {
       int point_id_1 = point_1.Key;
       int point_id_2 = point_2.Key;
       float similarity = selected_similarity_measure(point_1.Value, point_2.Value);

       Pr_Matrix.AddOrUpdate(point_id_1, 
       new ConcurrentDictionary<int, float>() { Keys = {  point_id_2 }, Values = { similarity } }, 
       (x, y) => y.AddOrUpdate(point_id_2, similarity, (m, n) => n));
   }
}

我无法更新主ConcurrentDictionary中存在的ConcurrentDictionarys。

Answer 1

第一个问题是AddOrUpdate方法返回一个浮点数据类型。必须显式返回ConcurrentDictionary：

  Pr_Matrix.AddOrUpdate(point_id_1, new ConcurrentDictionary<int, float>() { Keys = { point_id_2 }, Values = { similarity } }

                        , (x, y) => { y.AddOrUpdate(point_id_2, similarity, (m, n) => n); return y; });

第二个问题是键和值集合是只读的，而ConcurrentDictionary不支持集合初始值设定项，因此必须使用类似字典的方式对其进行初始化

Pr_Matrix.AddOrUpdate(
    point_id_1, 
    new ConcurrentDictionary<int, float>(new Dictionary<int, float> {{point_id_2, similarity}} ), 
    (x, y) => { y.AddOrUpdate(point_id_2, similarity, (m, n) => n); return y; }
);