How to resolve QLibrary issue

Hi,

I have a dll that can't re-enter, that is, it is not thread safe. But I need to call it repeatedly and it takes a lot of CPU time. So I am trying to use QtConcurrent and QLibrary.

However, QLibrary opens same dll and shares among themself. How can I make them not share?

The attached code gives same "addTo" and "getResult", and final results are wrong.

addTo = 0x7fcf487e063c, getResult = 0x7fcf487e0654
addTo = 0x7fcf487e063c, getResult = 0x7fcf487e0654
addTo = 0x7fcf487e063c, getResult = 0x7fcf487e0654
addTo = 0x7fcf487e063c, getResult = 0x7fcf487e0654
addTo = 0x7fcf487e063c, getResult = 0x7fcf487e0654

Any solution?

Thanks!

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Originally Posted by lni

How can I make them not share?

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You can't. That's the idea of having a shared library that there is one instance of it.

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Any solution?

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Perform calculations in separate processes or make the library re-entrant and thread-safe (the terms are not the same).

Quote:

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Originally Posted by wysota

You can't. That's the idea of having a shared library that there is one instance of it.


Perform calculations in separate processes or make the library re-entrant and thread-safe (the terms are not the same).

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I can't change the dll codes. It is a huge messy mathematical program.

But how I can I do calculations in separate processes? If I make an exe out of it. I would have to call it 1000000 times (with initialization as well), that would be even slower...

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Added after 25 minutes:

Here is my findings: for each thread, I copy the dll to a new name, open with QLibrary, then immediately delete it. The result appears to be good. See the attached codes.

Is there any potential problem here?

Thanks!

Quote:

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Originally Posted by lni

But how I can I do calculations in separate processes? If I make an exe out of it. I would have to call it 1000000 times

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No, not really. You'd have to call it as many times as you want operations to run in parallel. Each such instance would do many calculations in sequence.

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(with initialization as well), that would be even slower...

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Did you test it?

Quote:

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Here is my findings: for each thread, I copy the dll to a new name, open with QLibrary, then immediately delete it. The result appears to be good. See the attached codes.

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That's really... no, sorry, I just have to say it.... that's really stupid.