Question

    private static Int64 DirectoryBytes(String path)
    {
        var files = Directory.EnumerateFiles(path);
        Int64 masterTotal = 0;
        ParallelLoopResult result = Parallel.ForEach<String, Int64>(
        files,
        () =>
        { // localInit: Invoked once per task at start
            // Initialize that this task has seen 0 bytes
            return 0; // Set taskLocalTotal initial value to 0
        },
        (file, loopState, index, taskLocalTotal) =>
        { // body: Invoked once per work item
            // Get this file's size and add it to this task's running total
            Int64 fileLength = 0;
            FileStream fs = null;
            try
            {
                fs = File.OpenRead(file);
                fileLength = fs.Length;
            }
            catch (IOException) { /* Ignore any files we can't access */ }
            finally { if (fs != null) fs.Dispose(); }
            return taskLocalTotal + fileLength;
        },
        taskLocalTotal =>
        { // localFinally: Invoked once per task at end
            // Atomically add this task's total to the "master" total
            Interlocked.Add(ref masterTotal, taskLocalTotal);
        });
        return masterTotal;
    }

这是我从一本书中得到的一段代码。我对此有疑问。变量tasklocaltotal将处于线程级别或任务级别。根据本书，它处于任务级别，但由于线程可以执行多个任务，因此变量在整个程序执行过程中保持其值的方式。我认为它应该在线程级别。

有人可以提供有关此内容的见解以及可能的更多链接，以便我可以更清楚地了解这一概念。

.NET 4.0中的Parallel.ForEach

0 个答案: