使用parallel.foreach局部变量 [英] using local variables in parallel.foreach

问题描述

我有一个很艰难的时期工作了这一点。

在code应该从一个文件对话框导入图像。和每个图像应该是处理和发送到类正确的。 处理器是检测造型类，所以基本上我送每一个形象，并检测它的形状（类处理器内过滤到一定的标准）

newList将得到所有形状的中心的图像。

我在平行的小知识，我似乎无法弄清楚如何工作了这一点。 请记住，我并不需要从一个循环传递什么到另一个。我只想图像处理和纠正每次的时间，与整个操作分为主题。

  

我每次迭代一个独立的之一，我不需要从一个迭代到另一个返回任何东西。

目前的问题是，结果从类返回正确有时不正确。我想这是因为处理器和newList还必须是本地的？如果是的话我怎么能解决这个问题？如果不是我在哪里出了错？

另外请记住，使用普通的foreach工作得很好

下面是我的code：

  Parallel.ForEach（ofd.FileNames，
        （文件）=＆GT;
        {
            图片考试= Image.FromFile（文件）;
            VAR cvImage =新图片＆LT; BGR，字节＆GT;（（位图）考试）;
            处理器= processorMain;
            processor.ProcessImage（cvImage）;
            名单＆LT;点＆GT; newList =新名单，其中;点＆GT;（）;
            newList = processor.getList（）;
            correct.correct（cvImage，answerKey，nOptions）;
        }）;
 

解决方案

在注释中的实际问题/问题指出：

  

我每次迭代一个独立的之一，我不需要从一个迭代到另一个返回任何东西。

在这种情况下，你不希望你的图片 s到是线程本地的，你只需要他们的地方。因此该解决方案是简化：

  Parallel.ForEach（ofd.FileNames，
    （文件）=＆GT;
    {
        VAR cvImage =新图片＆LT; BGR，字节＆GT;（（位图）考试）;
        处理器= processorMain;
        processor.ProcessImage（cvImage）;
        名单＆LT;点＆GT; newList =新名单，其中;点＆GT;（）;
        newList = processor.getList（）;
        correct.correct（newList，cvImage，answerKey，nOptions）;
    }）;
 

但你的code没有真正使用文件任何地方，所以这只是一个粗略的猜测。这不可能是正确的呢。

而在另一方面，的用法 processorMain ， answerKey 和 nOptions 的潜在问题。

---

和之后多了一些意见，你需要的是：

 的IList＆lt;图像＆GT;结果= ofd.FileNames
       .AsParallel（）
       。选择（（文件）=＆GT;
{
    图片考试= Image.FromFile（文件）;
    ...
    返回考试;
}）了ToList（）。
 

I'm having a really hard time working this out.

The code is supposed to import images from a file dialog. And each image is supposed to be processed and sent to class correct. Processor is a class that detects shapes, so basically I am sending every image and detecting shapes in it(filtered to a certain criteria within the class processor)

newList will get the centers of all the shapes in an image.

I have little knowledge in Parallelism and I can't seem to figure how to work this out. Keep in mind that I do not need to pass anything from one iteration to another. I just want images to be processed and corrected each at a time, with the entire operation divided to threads.

I have every iteration a stand alone one and I need not return anything from one iteration to another.

Currently the problem is that the results returned from class correct are sometimes incorrect. i guess it is because processor and newList must also be local? If yes how can I solve this? If not where have I gone wrong?

Also keep in mind that using a normal foreach works just fine

Here is my code:

Parallel.ForEach(ofd.FileNames,
        (file) =>
        {
            Image exam = Image.FromFile(file);
            var cvImage = new Image<Bgr, byte>((Bitmap)exam);
            processor = processorMain;
            processor.ProcessImage(cvImage);
            List<Point> newList = new List<Point>();
            newList = processor.getList();
            correct.correct(cvImage, answerKey, nOptions);
        });

解决方案

The actual question/problem was stated in a comment:

I have every iteration a stand alone one and I need not return anything from one iteration to another.

In that case you do not want your Images to be Thread-local, you just need them local. So the solution is to simplify:

  Parallel.ForEach(ofd.FileNames,
    (file) =>
    {
        var cvImage = new Image<Bgr, byte>((Bitmap)exam);
        processor = processorMain;
        processor.ProcessImage(cvImage);
        List<Point> newList = new List<Point>();
        newList = processor.getList();
        correct.correct(newList, cvImage, answerKey, nOptions);
    });

But your code is not really using file anywhere so this is just a rough guess. It cannot be correct yet.

And on the other hand, the usages of processorMain, answerKey and nOptions are potential problems.

---

And after a few more comments, what you need is:

IList<Image> result = ofd.FileNames
       .AsParallel()
       .Select( (file) => 
{
    Image exam = Image.FromFile(file);
    ...
    return exam;
}).ToList();

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