COMSOL not using all memory available

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Hello,

I was trying to run a COMSOL simulation and it would always go over the available amount of RAM and start using Virtual Memory, which was extremely slow. Therefore, I bought more RAM (went from 64gb to 128gb), but COMSOL doesn't seem to want to use the full amount it has available. Indeed, once it reaches 64gb, it starts to write on the disk again even though there is still twice as much RAM available. Thinking that this was because COMSOL didn't "recognize" that there is more RAM, a clean install was done of COMSOL MultiPhysics, but this didn't solve the problem. Furthermore, I also tried to disable the use of Virtual Memory to force COMSOL to use the available RAM, but the simulation ends when COMSOL reaches the 64gb mark, with an error saying that there wasn't enough memory.

Why does COMSOL not use the full amount of RAM available?

Thanks in advance for your help!

Marek


4 Replies Last Post 13 déc. 2025, 13:47 UTC−5
Edgar J. Kaiser Certified Consultant

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Posted: 5 months ago 11 juil. 2025, 13:25 UTC−4

Did you check if the operating system recognizes the memory extension?

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Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Did you check if the operating system recognizes the memory extension?

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Posted: 5 months ago 11 juil. 2025, 13:58 UTC−4

Yes I checked and the operating system does recognize it. I was even able to create a 120gb matrix using MATLAB.

Yes I checked and the operating system does recognize it. I was even able to create a 120gb matrix using MATLAB.

Edgar J. Kaiser Certified Consultant

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Posted: 5 months ago 11 juil. 2025, 14:43 UTC−4

I recommend to submit this to COMSOL support.

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Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
I recommend to submit this to COMSOL support.

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Posted: 2 hours ago 13 déc. 2025, 13:47 UTC−5

this usually happens because COMSOL is limited by how it is configured and the solver being used, not by the total physical RAM installed. Even on systems with 128 GB RAM, COMSOL may start swapping at ~64 GB due to solver-specific memory limits, Java heap restrictions, or NUMA-related constraints. Using direct solvers (like MUMPS or PARDISO) can also trigger early disk usage because of internal memory handling. Ensuring the 64-bit version is used and checking solver and memory settings often helps.

Site owner, Sweet Bonanza 1000

this usually happens because COMSOL is limited by how it is configured and the solver being used, not by the total physical RAM installed. Even on systems with 128 GB RAM, COMSOL may start swapping at ~64 GB due to solver-specific memory limits, Java heap restrictions, or NUMA-related constraints. Using direct solvers (like MUMPS or PARDISO) can also trigger early disk usage because of internal memory handling. Ensuring the 64-bit version is used and checking solver and memory settings often helps. Site owner, [Sweet Bonanza 1000](http://sweet-bonanza-1k.com)

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