Memory issue
Altair EmployeeI want to simulate a hole array filter but I'm having trouble with memory usage. At first I would get an error saying insufficient memory available so I made the mesh much more coarse but it still took over 24 hours to run the solver. Any suggestions?
Answers
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Could you attach the *.out file here?
It seems that something is slowing down the simulation at the 6th frequency. We're currently investigating.
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Altair Forum User said:
Could you attach the *.out file here?
It seems that something is slowing down the simulation at the 6th frequency. We're currently investigating.
Thank you so much for taking the time to do this.
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Hi Pavlam
There seems to be a slow down problem with this specific model.
On my machine it runs 46x faster with FEKO version 2017.2. (Note I only tested frequency=900 GHz)
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Hi Pavlam,
The reason for the runtime issue is still under investigation. It could be worked around by setting up the unit cell differently:
Note that your mesh setting of lambda/5 does reduce the memory requirement, but will most likely not lead to trustworthy results. The unit cell has a size of 1.6 x lambda and thus will demand some memory with a mesh size of lambda/10 (>20 GByte). I see from your *.out file that you have 64 GByte installed, so that should not be a problem.
BUT: Due to the size of the unit cell there are grating lobes for each frequency (Grating Lobes). They prevent an accurate calculation of the transmission / reflection coefficients. A simple workaround here is shown here:
Note, P_incident is calculated by 2nd model, with no geometry present, just calculating the power going through NF front.
I will add the files here once the simulation has finished.
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Regarding grating lobes, maybe also read
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The files are now attached. Looking at the results I have to admit that they could look better (Rx+Tx =! 1 here and there). Most likely this can be improved by a larger distance between unit cell and near field requests. I chose 1 lambda at highest frequency, but looking at JIF's link, 10 lambda at lowest frequency probably would have been much wiser.
<?xml version="1.0" encoding="UTF-8"?>
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Altair Forum User said:
Hi Pavlam
There seems to be a slow down problem with this specific model.
On my machine it runs 46x faster with FEKO version 2017.2. (Note I only tested frequency=900 GHz)
Yes, 2017 definitely ran it faster. Thank you for the recommendation it helped a lot
Altair Forum User said:Hi Pavlam,
The reason for the runtime issue is still under investigation. It could be worked around by setting up the unit cell differently:
<?xml version="1.0" encoding="UTF-8"?>
This geometry was much simpler and easier to run. I would have never thought of this. Thank you for taking the time to do all this, I really appreciate it.
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Hi Pavlam,
One imoprtant addition: The calculation the Rx / Tx coefficients from the power flow through near field is only well-defined if the size of the near field requests is N * size of unitcell (N is an arbitrary interger value). In your case the size could be dy*dz or dy*2dz,...
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