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The other problem; out of memory during LU factorization

Posted 27.12.2015, 11:06 GMT-5 Low-Frequency Electromagnetics, Studies & Solvers Version 5.2a 3 Replies

Hyunjae Lee
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Hello, everyone
I have a little different problem with others
First, my error message is similar with the others

"Failed to find a solution.
Out of memory during LU factorization.
Returned solution is not converged."

The real problem is, however, I upgrade my computer RAM from 32 GB to 256GB to solve quite large and complicated models. Meanwhile, the model that I calculated was only 5M DOF. It seems to be solved within 64GB. I believe that. Furthermore, the error ocurred at around 30GB or 50GB (according to different solvers)

Here is the question. Why did the error happen at 30 or 50GB even though my computer had 256GB RAM.

ps. I used AC/DC module/ magnetic field/ frequency domain only
3 Replies Last Post 14.02.2017, 16:14 GMT-5
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Hello Hyunjae Lee

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Bernd Walkenfort
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Posted: 8 years ago 14.02.2017, 08:11 GMT-5
Hello everyone,

isn't there any answer or help?
I have the same problem, that comsol just uses the RAM between 30-50GB instead of 110GB.

The predefinde aplication work fine, they just use 3-5Gb of RAM and i had other Siumulations running with at least 100GB working.
Hello everyone, isn't there any answer or help? I have the same problem, that comsol just uses the RAM between 30-50GB instead of 110GB. The predefinde aplication work fine, they just use 3-5Gb of RAM and i had other Siumulations running with at least 100GB working.
Jeff Hiller COMSOL Employee

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Posted: 8 years ago 14.02.2017, 16:00 GMT-5
Hello Bernd,
In my limited understanding of how these things work, the software calls for the OS to allocate memory in chunks before it can use that memory, so that allocated memory increases in steps, not continuously.
Is it possible that while up to that point in this particular solution process only 30-50GB have been needed, suddenly, say, an additional 100GB (which you don't have) is requested of the OS for the next step of the solution? This would explain why you run out of memory without ever getting close to "saturating" the 110GB.
Best,
Jeff
Hello Bernd, In my limited understanding of how these things work, the software calls for the OS to allocate memory in chunks before it can use that memory, so that allocated memory increases in steps, not continuously. Is it possible that while up to that point in this particular solution process only 30-50GB have been needed, suddenly, say, an additional 100GB (which you don't have) is requested of the OS for the next step of the solution? This would explain why you run out of memory without ever getting close to "saturating" the 110GB. Best, Jeff
Yi Yan
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Posted: 8 years ago 14.02.2017, 16:14 GMT-5
Thank you very much Jeff for your explanation.

I also would like to add one point that you may encounter. When I had a crashed job because of this Out of Memory error, I noticed that the allocated RAM won't be released if I only stopped and closed that job. To get all those allocated RAM free, I restarted my computer but recently I found just close all COMSOL programs would be fine enough.
Just let you guys know if you are stuck at that point.

Thanks a lot.
Yi
Thank you very much Jeff for your explanation. I also would like to add one point that you may encounter. When I had a crashed job because of this Out of Memory error, I noticed that the allocated RAM won't be released if I only stopped and closed that job. To get all those allocated RAM free, I restarted my computer but recently I found just close all COMSOL programs would be fine enough. Just let you guys know if you are stuck at that point. Thanks a lot. Yi

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