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Comsol 4.3a Memory problem -- not using enough RAM

Posted 3 feb 2013, 19:07 GMT-5 Studies & Solvers Version 4.3a 8 Replies

ajeetraj
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Hello everyone,

Usually the complain is that Comsol is using too much memory, but in my case its other way round.


I have a really nice machine in the lab with windows 8 server. I have Comsol version 4.3a installed. I am trying to run an RF module computation, where I am trying to create a fine mesh.

My problem is that even though the computer has 256 GB or RAM, the comsol uses only 1.2 GB or so maximum. Also, I have a 16 core x 2 processor but it uses only 3.5% of the cpu at max.

Coule anyone please explain to me if there is a way to overcome this problem. did anyone else have the same problem?

Thanks in advance.
8 Replies Last Post 26 gen 2015, 15:49 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 4 feb 2013, 01:06 GMT-5
Hi

Check the earlier threads, some solvers cannot use multiprocessing, and several operations are not paralellised, or cannot easily be made so. By default COMSOL will choose at much RAM required and available, and use at least half of all your processors

--
Good luck
Ivar
Hi Check the earlier threads, some solvers cannot use multiprocessing, and several operations are not paralellised, or cannot easily be made so. By default COMSOL will choose at much RAM required and available, and use at least half of all your processors -- Good luck Ivar
ajeetraj
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Posted: 1 decade ago 4 feb 2013, 09:51 GMT-5
So in order to use multiple processors, I checked the options of Comsol and changed the number of processors from 1 to the value I have and it seems like it can use many processors. Nevertheless, for the meshing, it still uses around 700MB maximum. At the bottom it always stays

Working set: around 670MB | virtual 780MB.

After changing the number of processors, the cpu %age went up but after 5 minuts the cpu usage stays between 2.5% to 3% and of course it takes forever to mesh. My first trial of meshing is still not done.

Any help would be greatly appreciated.

Thanks Mr. Ivar Kjelberg for your quick response!

So in order to use multiple processors, I checked the options of Comsol and changed the number of processors from 1 to the value I have and it seems like it can use many processors. Nevertheless, for the meshing, it still uses around 700MB maximum. At the bottom it always stays Working set: around 670MB | virtual 780MB. After changing the number of processors, the cpu %age went up but after 5 minuts the cpu usage stays between 2.5% to 3% and of course it takes forever to mesh. My first trial of meshing is still not done. Any help would be greatly appreciated. Thanks Mr. Ivar Kjelberg for your quick response!
Anosh Daruwalla
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Posted: 1 decade ago 12 giu 2013, 14:53 GMT-4
I am facing a similar problem for the transient solver. Any solution or further update on this issue would be greatly appreciated :)
I am facing a similar problem for the transient solver. Any solution or further update on this issue would be greatly appreciated :)
Felipe Beltran-Mejia
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Posted: 1 decade ago 13 giu 2013, 12:22 GMT-4
Hi All,

In this entry: www.comsol.com/support/knowledgebase/830/

Comsol's staff give some advices such as augmenting the Java Heap Memory, which is the place where the different solutions are stored.

To my surprise, I've found out the default value for the Java Heap Size is quite low (1Gb). They recommend doubling it, but I had went further and multiplyed it by a factor of 10. Altough it didn't seems to change much (at least for me).
--
cheers,
Felipe BM
Hi All, In this entry: http://www.comsol.com/support/knowledgebase/830/ Comsol's staff give some advices such as augmenting the Java Heap Memory, which is the place where the different solutions are stored. To my surprise, I've found out the default value for the Java Heap Size is quite low (1Gb). They recommend doubling it, but I had went further and multiplyed it by a factor of 10. Altough it didn't seems to change much (at least for me). -- cheers, Felipe BM
Gunnar Andersson COMSOL Employee

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Posted: 1 decade ago 14 giu 2013, 02:23 GMT-4

Comsol's staff give some advices such as augmenting the Java Heap Memory, which is the place where the different solutions are stored.


This isn't quite correct: The solutions are not stored in the Java heap. If you increase the Java heap a lot, then you will decrease the memory that can be used for solving the model - quite the opposite of what you want.

In general, I advice you to not experiment with the Java heap settings unless you have received from support to do so.


[QUOTE] Comsol's staff give some advices such as augmenting the Java Heap Memory, which is the place where the different solutions are stored. [/QUOTE] This isn't quite correct: The solutions are not stored in the Java heap. If you increase the Java heap a lot, then you will decrease the memory that can be used for solving the model - quite the opposite of what you want. In general, I advice you to not experiment with the Java heap settings unless you have received from support to do so.
Felipe Beltran-Mejia
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Posted: 1 decade ago 14 giu 2013, 07:29 GMT-4
Thanks for the feedback Gunnar.

Then I believe the referenced knowledgebase shall be corrected, since (for me) that is what it says:

"Of the available memory (RAM and virtual memory), one section, the Java heap, is reserved for Java and will be used for storing the different solutions in the model.( ...) The rest of the memory will be available for meshing and solving. (....)"

Thanks for claryfying, I'll return my confs to their default values.
--
cheers,
Felipe BM
Thanks for the feedback Gunnar. Then I believe the referenced knowledgebase shall be corrected, since (for me) that is what it says: "Of the available memory (RAM and virtual memory), one section, the Java heap, is reserved for Java and will be used for storing the different solutions in the model.( ...) The rest of the memory will be available for meshing and solving. (....)" Thanks for claryfying, I'll return my confs to their default values. -- cheers, Felipe BM
Jim Freels mechanical side of nuclear engineering, multiphysics analysis, COMSOL specialist
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Posted: 1 decade ago 15 giu 2013, 12:07 GMT-4
Is your machine a 32-bit or 64-bit ? If a 64-bit, is your OS setup to run in 64-bit ?

In order for a single application, e.g. COMSOL, to use a lot of memory, both the hardware and OS must be running in 64-bit mode. Otherwise, the most memory ANY application, including COMSOL, can use in 32-bit mode is 2^31 or about 2GB or less. This sounds like what you may be doing.

If all is running 64-bit, make sure if you are running Windows, you click the 64-bit COMSOL start icon and not the 32-bit COMSOL start icon.

Is your machine a 32-bit or 64-bit ? If a 64-bit, is your OS setup to run in 64-bit ? In order for a single application, e.g. COMSOL, to use a lot of memory, both the hardware and OS must be running in 64-bit mode. Otherwise, the most memory ANY application, including COMSOL, can use in 32-bit mode is 2^31 or about 2GB or less. This sounds like what you may be doing. If all is running 64-bit, make sure if you are running Windows, you click the 64-bit COMSOL start icon and not the 32-bit COMSOL start icon.
Jorge Hernandez
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Posted: 10 years ago 26 gen 2015, 15:49 GMT-5
Hi all,
What happens is that your solver is saving files in order to save RAM.
If this is not desirable ( you have tons of RAM and you find it faster, like me) then you can un-check the option of "store solution out-of-core" box, it is in your "Time dependent solver" options.
Hope this helps!
if you do this, and then you figure out how to clear the memoru without having to close and open again the server I would be very grateful.
Best,
Hi all, What happens is that your solver is saving files in order to save RAM. If this is not desirable ( you have tons of RAM and you find it faster, like me) then you can un-check the option of "store solution out-of-core" box, it is in your "Time dependent solver" options. Hope this helps! if you do this, and then you figure out how to clear the memoru without having to close and open again the server I would be very grateful. Best,

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