下面的代码只是创建一个List> of random numbers,然后计算并行foreach循环中每个列表的累积和 . 为什么我得到的数字少于'numLists'?通常在9990左右 . 我猜它与线程安全有关 . 什么是替代方法? (我是C#初学者,所以希望我使用正确的术语)谢谢 .
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
namespace testParallelForeach
{
class Program
{
static void Main(string[] args)
{
List<List<double>> bsData = new List<List<double>>();
List<List<double>> cumsumDataP = new List<List<double>>();
int numLists = 10000;
int myLen = 400;
Random rand = new Random();
for (int i = 0; i < numLists; i++)
{
bsData.Add(new List<double>());
for (int j = 0; j < myLen; j++)
{
bsData[i].Add(rand.NextDouble());
}
}
Parallel.ForEach(bsData, a => cumsumDataP.Add(CumulativeSumParallel(a)));
Console.WriteLine("cumsumDataP.Count={0}", cumsumDataP.Count);
Console.ReadKey();
}
public static List<double> CumulativeSumParallel(List<double> singleRetSeries)
{
int r = singleRetSeries.Count;
List<double> cumsumList = new List<double>();
cumsumList.Add(singleRetSeries[0]);
for (int i = 1; i < r; i++)
{
cumsumList.Add(cumsumList[i - 1] + singleRetSeries[i]);
}
return cumsumList;
}
}
}
1 回答
List<T>
确实不是线程安全的,所以cumsupDataP.Add(...)
正在以不可预测的方式丢弃数据 .将该行替换为:
这一切都会奏效 . 请注意
ConcurrentBag<T>
是无序的,但这很好,因为无论如何你无法预测线程的顺序; p