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Trying to include an external dll (compiled from c)
Posted 14 gen 2024, 11:15 GMT-5 API, Modeling Workflow, User Interface Version 6.2 3 Replies
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Hello,
I am trying to use a custom function in comsol. For testing purposes, I have written a short c file:
double f(double x, double y, double z);
double f(double x, double y, double z) {
double r;
r = x * (1 + 1*(y-z) + 1*(y-z));
return r;
}
Then I compiled my code as adviced on suggested on cygwin with the commands gcc -c test.c and then gcc -shared -o test.dll test.o.
Now in Global Definitions, I created a new instance with right click -> functions -> extern, filled out function name with "f" and arguments with "x, y, z" and finally created 3 entries in plot parameters ranging from 0 to 10 for every entry.
Now if I click "plot" or "create plot" I get an error saying "Symbol not found". I have googled and asked Bing "to google for me" but I dont find any resource that helps me here.
How do I make this work?
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Hi Maximilian,
For an external function in COMSOL Multiphysics, you must define three functions: init, eval, and getLastError, and for the numerical evaluation, the input and output arguments must be arrays (x, y, and z in your example and in general are numerical arrays). See the COMSOL Multiphysics Programming Reference Manual for more information and an example.
Best regards,
Magnus
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Hi Maximilian,
For an external function in COMSOL Multiphysics, you must define three functions:
init,eval, andgetLastError, and for the numerical evaluation, the input and output arguments must be arrays (x, y, and z in your example and in general are numerical arrays). See the COMSOL Multiphysics Programming Reference Manual for more information and an example.Best regards,
Magnus
Thank you for your anwser. Could you tell me where exactly you found the example in the manual? I search for a bit, but couln't locate it.
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Thank you for your anwser. Could you tell me where exactly you found the example in the manual? I search for a bit, but couln't locate it.
Hi Maximilian,
It's located in the COMSOL Multiphysics Programming Reference Manual, under General Commands>About General Commands>model.func(). Then scroll down to External.
Best regards,
Magnus