Learning Forum

[asimghalib]

I have a PC with 64 GB RAM and 64 bit operating system. When i try to find the Characteristic modes of a geometry, it runs into this problem "Out of memory", Any suggestions to avoid such problem

[mahmed]

Does this error pop up during the simulation or after?

[asimghalib]

Does this error pop up during the simulation or after?

 

The error came during the simulation. I decreased the mesh density to the least (which i think is not OKAY) and then i did not faced the problem but I am still curious why this error was coming. If HFSS doesnot have enough space on RAM, it shall use the Hard disk automatically. I have enough space on Hard disk.

 

 

[mahmed]

No, there's a difference between RAM and disk space. RAM is the space required for running a specific project while the disk space is used to save the project results. 

As you mentioned decreasing the mesh density to the least isn't causing any issues. So, it can be said that your project design with an average mesh density requires more than 64GB RAM to run to completion. So please try using a machine with a higher RAM.

[asimghalib]

Thank You mahmed.

yes, it seems to me too. I thought 64 GB RAM is sufficient for mm waves.

Dear, what should be the specification of the PC like RAM etc to do millimetre wave solution? Is there a way we can work with the same RAM?

[mahmed]

There are several factors which might lead to a denser mesh like the complexity of the model, operating frequency, etc...

If possible, I would suggest you to decrease the operating frequency and give it a try.

[asimghalib]

At lower frequencies like 2GHz, the simulation is working fine. So that is why I am confused about the RAM requirements. In Driven terminal solution type if we encounter "out of memory error" we can address it by changing it into the iterative solver. Now the will take more time but will not give this error.

So is there any alternative to run it without increasing the RAM?

[mahmed]

Yes at lower frequencies the mesh size decreases significantly. If you can see in the profile, there is a row which shows the lambda based mesh, which is dependent on frequencies. Lowering the operating frequency decreases the overall mesh density thereby decreasing the computing power which ends up using less RAM.

Please go to the help section and read the difference between the different solution types and what are the tradeoffs of using them.

 

 

[mahmed]

Regarding iterative solver,

 

How many excitations do you have in your model?

[asimghalib]

Thank you mahmed 

Thanks

The problem is that I can see the mesh and the size of the disk used after the simulation ends. During the simulation when I check the computing resources used by the different programs the ANSYS is using only 30% and is not increasing this confuses me a lot.

The second question is that now I am using the lower mesh density but the simulation is not completing at all. it seems it is running forever. its more than 2 days and is running. I am not using a frequency sweep, it is just a simulation at a single point and no adaptive passes. Any idea.?

[asimghalib]

Dear, it is characteristic mode analysis. Its done in the absence of an excitation source.

[mahmed]

Please check the memory tab instead of the disk tab in the task manager. And after simulation finishes, the memory returns back to the average value. You need to monitor the memory while the simulation is up and running/or when it gives the out of memory error.

The wait time is expected, if you are computing a complex model. What kind of a project are you simulating?

[Kanan]

 please can anyone help me with the latest version of HFSS that supports CMA. Anytime i run, it presents simulation error. I'm confused.

[ChiniWotsu]

I also have so many errors when run CMA in HFSS 2020R2. Sometimes can work but most time cannot. Can anyone provide tutorials about CMA in HFSS or a release book. There is little information online.n