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CADFEKO critical error pk_error_tag_limit_exceeded when creating many unit cells via Lua macro

qiut_2k

Hi,

I am using a Lua macro in CADFEKO to programmatically generate a large periodic structure for multiport analysis. The geometry creation involves operations such as creating patches, vias, and assigning edge ports.

The script works correctly for smaller models, but when the total model becomes sufficiently large, CADFEKO crashes with the critical error PK_ERROR_tag_limit_exceeded.

I was wondering whether anyone has encountered this issue before, and if there are any recommended workarounds or best practices for building large scripted models for multiport analysis without hitting this limitation.

Any suggestions would be greatly appreciated.

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Feko

v2026.0

Accepted answers

Torben Voigt

Hi Tianke,

Regarding the Sweep label, I think the behaviour is expected. You can still rename the sweep using code like this:
-- Setting Label sweep1 = application.Project.Contents.Geometry:Item("Sweep1")

sweep1.Label = "MySweep"

See label_sweep_alt.lua.

label_sweep_alt.lua

Still not sure what's the problem with the create_ports.lua script, but happy you found a workaround with create_structure_ports_merged.lua.

Best regards,
Torben

Torben Voigt

Hi Tianke,

As a general rule, I would advise against modeling the physical thickness of the dipoles. This drastically reduces the number of mesh elements required and saves a significant amount of memory and runtime.

All comments

Torben Voigt

Hi @qiut_2k ,

Is the problem reproducible, or does it happen randomly? I could imagine that there might actually not be enough available RAM. Could you test with less elements / try to see if the problem occurs when there’s a specific number of elements?

Best regards,
Torben

qiut_2k

Hi Torben,

Thank you for your suggestion.

The issue appears to be reproducible. The error consistently occurs once the model reaches a certain number of unit cells. I tried generating a model with one fewer unit cell than the failing case, and it completed successfully. However, when I added just one more unit cell, the error occurred again.

I have also been monitoring the RAM usage during geometry generation, and the memory consumption remains relatively low when the error occurs, so it does not appear to be caused by insufficient memory.

Regards,

Tianke

Torben Voigt

Hi Tianke,

Could you try with Auto Mesh turned off?

Can you share the lua script so I can check on my machine?

Best regards,
Torben

qiut_2k

Hi Torben,

Auto meshing is already disabled in my model.

I did some additional testing and found something interesting. If I first generate all of the metallic structures and then run a separate script to create the edge ports, CADFEKO crashes with the PK_ERROR_tag_limit_exceeded error. This was my original workflow, since the geometry generation script is also used for other purposes. However, if I combine the geometry creation and port creation into a single loop, the script completes successfully.

I have attached a zip file containing the scripts in case you would like to reproduce the issue or take a closer look.

scripts.zip

I also included a short script demonstrating another issue I encountered. It appears that assigning a label to a sweep operation does not work as expected. In the example, I set the sweep label to my_sweep, but the resulting geometry is still assigned the default label Sweep1.

Thanks,

Tianke

Torben Voigt

Hi Tianke,

Thanks for the files. Another potential issue is the port visualization. I've noticed on several occasions that the GUI runs much faster when port visualization is disabled for a large number of ports. Perhaps there's a connection to the crashes. I'll test that out.

I'll look into the Sweep label issue as well.

Best regards,
Torben

Torben Voigt

Hi Tianke,

Regarding the Sweep label, I think the behaviour is expected. You can still rename the sweep using code like this:
-- Setting Label sweep1 = application.Project.Contents.Geometry:Item("Sweep1")

sweep1.Label = "MySweep"

See label_sweep_alt.lua.

label_sweep_alt.lua

Still not sure what's the problem with the create_ports.lua script, but happy you found a workaround with create_structure_ports_merged.lua.

Best regards,
Torben

Torben Voigt

Hi Tianke,

qiut_2k

Hi Torben,

Thank you for the example for the Sweep label. This approach works, but it requires knowing the automatically assigned sweep label (e.g., Sweep1) beforehand. I was expecting the sweep operation to behave similarly to geometry creation commands such as AddRectangle, where the label can be assigned directly when the object is created, without needing to first determine its default name.

Regarding the create_ports.lua script, thank you for taking the time to look into it. If you happen to find an explanation in the future, I would be very interested to hear it.

Thanks,

Tianke

qiut_2k

Hi Torben,

Thank you for the suggestion. I will keep that in mind.

Tianke