nonlocal external functions

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Hi,

Depending on the grid size the custom function (matlab or external dll) may be called several times per evaluation step for different grid cell blocks (assembly block sizes). However, my function operations are non-local, i.e. the function must use (global) values outside the grid cells that is sent to the function, is there a way to get around this?

Thank you very much!


2 Replies Last Post 10 dic 2024, 20:15 GMT-5
Lars Gregersen COMSOL Employee

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Posted: 5 days ago 10 dic 2024, 03:02 GMT-5

There is no general way to get the MATLAB function calls (or external functions) to work on a global scale. You can increase the block size and see if that works for your model, but even then there is a limit to how large blocks can be.

You can see if you can generate a global operator (e.g. an integral, max/min or something similar) that uses your custom functions as inputs.

Alternatively, you can solve the model. Use the COMSOL API do extract the data and calculate the quantities you need. You can then feed the calculated data into your model and solve the model again if that is required.

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Lars Gregersen
Comsol Denmark
There is no general way to get the MATLAB function calls (or external functions) to work on a global scale. You can increase the block size and see if that works for your model, but even then there is a limit to how large blocks can be. You can see if you can generate a global operator (e.g. an integral, max/min or something similar) that uses your custom functions as inputs. Alternatively, you can solve the model. Use the COMSOL API do extract the data and calculate the quantities you need. You can then feed the calculated data into your model and solve the model again if that is required.

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Posted: 4 days ago 10 dic 2024, 20:15 GMT-5

Hi Lars,

Many thanks for your reply~ Could you let me how to increase the block size? And, I am wondering why the interface is designed to only send data in blocks? Thanks!

Hi Lars, Many thanks for your reply~ Could you let me how to increase the block size? And, I am wondering why the interface is designed to only send data in blocks? Thanks!

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