从MATLAB运行多进程应用程序 [英] Running multiprocess applications from MATLAB

问题描述

我在VC ++中编写了一个多进程应用程序，并尝试使用 system 命令。它运行，但只有一个核心 - 任何建议？

更新：实际上，它甚至看不到第二个核心。我使用OpenMP并使用 omp_get_max_threads（）和 omp_get_thread_num（）检查和 omp_get_max_threads当我从MATLAB执行应用程序时，似乎是 1 ，但它 2

：我的任务管理器报告CPU使用率接近100％---如果我从命令窗口运行它。这可能意味着上述API运行正在作为多进程应用程序运行？

确认：

使用 Process Explorer 检查线程数是否有任何差异。

当我从命令窗口调用应用程序时， 1 线程转到 cmd。 exe 和 2 转到我的应用程序。

26 线程适用于 MATLAB.exe ， 1 code> cmd.exe 和 1 。

$ p

解决方案

问题是Matlab是如何影响你的应用程序的行为，因为它是一个单独的过程。我怀疑Matlab正在以影响OMP的方式修改环境变量，也许是因为它在内部使用了OMP，而您从Matlab派生的进程正在继承此修改后的环境。

从命令窗口中执行一个set> plain.txt，您将在其中启动您的应用程序，和system（'set> from_matlab.txt'）从Matlab，并差异输出。这将显示Matlab介绍的环境变量的差异。当我这样做，这出现在继承自Matlab的环境中，但不是在纯命令窗口的环境中。

  OMP_NUM_THREADS = 1 
  

这看起来像一个与您的问题中的函数调用相关的OpenMP设置。我会打赌你生成的应用程序看到和尊重它。

我不知道为什么Matlab设置它。但是，作为解决方法，当您从Matlab启动应用程序，而不是直接调用它，调用一个包装器.bat文件，清除OMP_NUM_THREADS环境变量，或将其设置为更高的数字。

I've written a multitprocess application in VC++ and tried to execute it with command line arguments with the system command from MATLAB. It runs, but only on one core --- any suggestions?

Update:In fact, it doesn't even see the second core. I used OpenMP and used omp_get_max_threads() and omp_get_thread_num() to check and omp_get_max_threads() seems to be 1 when I execute the application from MATLAB but it's 2 (as is expected) if I run it from the command window.

Question:My task manager reports that CPU usage is close to 100% --- could this mean that the aforementioned API is malfunctioning it's still running as a multiprocess application?

Confirmation:

I used Process Explorer to check if there were any differences in the number of threads.

When I call the application from the command window, 1 thread goes to cmd.exe and 2 go to my application.

When I call it from MATLAB, 26 threads are for MATLAB.exe, 1 for cmd.exe and 1 for my application.

Any ideas?

解决方案

The question is how Matlab is affecting your app's behavior, since it's a separate process. I suspect Matlab is modifying environment variables in a manner that affects OMP, maybe because it uses OMP internally, and the process you are spawning from Matlab is inheriting this modified environment.

Do a "set > plain.txt" from the command window where you're launching you app plain, and "system('set > from_matlab.txt')" from within Matlab, and diff the outputs. This will show you the differences in environment variables that Matlab is introducing. When I do this, this appears in the environment inherited from Matlab, but not in the plain command window's environment.

OMP_NUM_THREADS=1 

That looks like an OpenMP setting related to the function calls in your question. I'll bet your spawned app is seeing that and respecting it.

I don't know why Matlab is setting it. But as a workaround, when you launch the app from Matlab, instead of calling it directly, call a wrapper .bat file that clears the OMP_NUM_THREADS environment variable, or sets it to a higher number.

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