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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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"Out of memory"

Posted 03.04.2013, 11:00 GMT-4 Version 4.3a 3 Replies

Astrid Billon
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Hello,

I have this system - a fiber optic cable glued on a concrete beam -, which I would like to calculate with Comsol.
When I use a Finer mesh (which brings c.a. 96 000 elements) everything goes alright. But I want to be more accurante, especially in the region of the fiber optic, and pass to Extra-Fine mesh (c.a. 500 000 elements). The computer then runs "Out of memory" (also by starting from a Finer mesh and then increasing the maxi/mini elements size and the resolution of narrow regions).
I believe my computer should be powerful enough to do it : 2 * 2.40Ghz and 12.0 Go of RAM. Is it ?

Can this be a mesh problem, even though I have the "Out of memory" problem ?

Thanks !

Regards,

Astrid.
3 Replies Last Post 04.04.2013, 07:50 GMT-4
Edgar J. Kaiser Certified Consultant
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Posted: 1 decade ago 03.04.2013, 11:51 GMT-4

Astrid,

very likely the DOF number is too high for your 12 GB RAM and you need to reduce the mesh resolution. However, your model looks like a 2D planar appoach could be justified, of course depending on what you exactly need to find out.

In 2D you wouldn't see any memory issues with this model.

--
Edgar J. Kaiser
www.emphys.com
Astrid, very likely the DOF number is too high for your 12 GB RAM and you need to reduce the mesh resolution. However, your model looks like a 2D planar appoach could be justified, of course depending on what you exactly need to find out. In 2D you wouldn't see any memory issues with this model. -- Edgar J. Kaiser http://www.emphys.com
Astrid Billon
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Posted: 1 decade ago 04.04.2013, 07:07 GMT-4
Dear Edgar,

Thank you for your quick answer.
I don't understand, though, that my computer can handle the calculation of this other model (for the file see link below), which has around 2 millions more dof.

www.partage-fichiers.com/upload/qlis3bnn

Are there geometries which are more "difficult" to handle and need more computation power for the same amount of dof ? or how could we explain that he can calculate this model with more dof but sends an "Out of memory" error message for the previous one ?

My final geometry, which I have eventually to compute, should have around twice more dof than in the attach file of my previous message (the fiber optic model). I can ask for more RAM to be installed on my computer. Could you help me to determine how much more I need ?

Thank you !
Regards,

Astrid.
Dear Edgar, Thank you for your quick answer. I don't understand, though, that my computer can handle the calculation of this other model (for the file see link below), which has around 2 millions more dof. http://www.partage-fichiers.com/upload/qlis3bnn Are there geometries which are more "difficult" to handle and need more computation power for the same amount of dof ? or how could we explain that he can calculate this model with more dof but sends an "Out of memory" error message for the previous one ? My final geometry, which I have eventually to compute, should have around twice more dof than in the attach file of my previous message (the fiber optic model). I can ask for more RAM to be installed on my computer. Could you help me to determine how much more I need ? Thank you ! Regards, Astrid.
Edgar J. Kaiser Certified Consultant
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Posted: 1 decade ago 04.04.2013, 07:50 GMT-4

Hi Astrid,

I took your model as provided and added a stationary study (there was no study node) and let it run on our big machine. It solved without problems and used 27 GB.

The mesh consisted of 326000 elements but the study has 1.600 000 DOF. Maybe you mix mesh elements and DOF here.

So with 32 GB you should be save, but I would ask for 64 if the mainboard allows it because RAM is fairly cheap these days. Make sure you run a 64 bit operating system.

Cheers
Edgar

--
Edgar J. Kaiser
www.emphys.com
Hi Astrid, I took your model as provided and added a stationary study (there was no study node) and let it run on our big machine. It solved without problems and used 27 GB. The mesh consisted of 326000 elements but the study has 1.600 000 DOF. Maybe you mix mesh elements and DOF here. So with 32 GB you should be save, but I would ask for 64 if the mainboard allows it because RAM is fairly cheap these days. Make sure you run a 64 bit operating system. Cheers Edgar -- Edgar J. Kaiser http://www.emphys.com

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