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c#multithreadingmatlab
NESHOM
NESHOM

Reputation: 929

Calling two functions from a single Matlab dll at the same time

I have created a Matlab dll that includes two functions. Function1 takes 3-4 millisecond to run and Function2 takes around 1 second. I need to run Function1 in C# continuously and Function2 time to time. I experienced that when I run Function2, Function1 does not run continuously or it takes a lot more than 3-4 millisecond (something in the range of 2-3 second). Function1 returns to normal/fast state as soon as Function2 is completed. These are what I already tried:

  1. I called Function2 in a separate Thread, with no luck! (Function1 is also running in a separate Thread).
  2. I used backgroundworker instead of Thread (just in case), with no luck!
  3. I created a separate dll just for Function2, and again I experienced same issue/delay/latency.

Does anyone have any idea/solution for this problem? Does Matlab run functions/code in single thread? If not, is there anyway to specify separate thread for Functions?

I appreciate any help.

Upvotes: 3

Views: 907

Answers (1)

Douglas
Douglas

Reputation: 54887

It seems like your intuition is correct: Calls to Matlab libraries are executed sequentially, even if originating from multiple threads. Refer to the comments by Peter Webb under Creating C++ Shared Libraries and DLLs:

You can call the libraries from multiple threads, but only one thread can be active in a library at any time. The generated libraries are protected by semaphores, which only allow one user thread into the generated library at any one time. Other user threads that try to call into the shared library will block (wait) until the shared library is “free”.

[...]

The libraries protect themselves with semaphores. They do so because the underlying execution engine (the MCR) is not thread safe. This means that even if you could disable the semaphores, you wouldn’t want to, since you’d likely get incorrect results or program failures.

If you truly need parallelism, currently your best (and only) option is to use separate processes. If your client can speak any of the standard web protocols (HTTP or JSON) or Microsoft’s proprietry extended versions, it’s pretty simple to set up web-based WCF clients in separate processes using WCF. (Of course, your servers have to run on Windows machines in that case.) See my WCF post for details.

Upvotes: 2

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