c# - Parallel.ForEach 与元组返回 c#

Question

基于此example我正在尝试使用元组返回进行并行 foreach。

double min = double.MaxValue;

object syncObject = new object(); 
Parallel.ForEach(collection, () => double.MaxValue, (item, loopState, 
    localState) =>
    {
        double value = item.PerformComputation();
        return System.Math.Min(localState, value);
    },
    localState =>
    {
        lock(syncObj)
            min = System.Math.Min(min, localState);
    }
);

Console.Write(min + "\n");

上面的代码工作正常但在我的场合(正确的最小值)但我不想输出最小值而是该值的“名称”所以我尝试了这样的事情:

double min = double.MaxValue;
string minName = "";

object syncObject = new object(); 
Parallel.ForEach(collection, () => Tuple.Create(double.MaxValue, ""), (item, 
    loopState, localState) =>
    {
        double value = PerformComputation(item.Item1.Value);
        string name = item.Item1.Key;

        return //helpHere
    },
    localState =>
    {
        lock(syncObj)
            min = //help here
            minName = //help here
    }
);

Console.Write(minName + "\n");

尝试了一些没有用的东西。我也读过microsoft's example没有运气。任何帮助表示赞赏。

Answer 1

您的问题中没有太多上下文。最好能给个好的Minimal, Complete, and Verifiable code example这表明你在做什么。但是，它看起来好像在您的第二个版本的代码中，您已经从一个带有 PerformComputation() 的对象更改了计算模型。方法，到一个PerformComputation()本地定义的方法，以及某种 Tuple 的集合对象，其中 Item1成员是 KeyValuePair<TKey, TValue>某种形式。

做出这些假设，这样的事情应该适用于您的场景:

Tuple<double, string> result = Tuple.Create(double.MaxValue, "");

object syncObject = new object(); 
Parallel.ForEach(collection, () => Tuple.Create(double.MaxValue, ""),
    (item, loopState, localState) =>
    {
        double value = PerformComputation(item.Item1.Value);

        if (value < localState.Item1)
        {
            localState = Tuple.Create(value, item.Item1.Key);
        }

        return localState;
    },

    localState =>
    {
        lock(syncObj)
        {
            if (localState.Item1 < result.Item1)
            {
                result = localState;
            }
        }
    }
);