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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 The information provided may be out of date.

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Later version of COMSOL has robuster and stabler solvers

Posted Dec 29, 2012, 8:46 a.m. EST Studies & Solvers Version 4.3, Version 4.3b 4 Replies

Pu
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Dear all,

I just want to share my recent experience with a convergence problem.

During last several weeks I was struggling with convergence problem. The model has two 2nd-order PDE and Electromagnetic Waves application modes coupled together. I was using 4.2a and 3.5a. (I thought there might not be big difference between 4.2a and 4.3a.) However neither secured convergence. After those painful time, I asked technical support (perhaps I should ask earlier...). The answer was so simple: use the latest version. And it works! I almost don't need to change anything. How long time I wasted...

The lesson is trust in newer version :)

Best
--
Pu, ZHANG ??
Departamento de Física Teórica de la Materia Condensada,
Universidad Autónoma de Madrid,
Madrid, Spain.
4 Replies Last Post Sep 11, 2013, 12:52 p.m. EDT
Jim Freels mechanical side of nuclear engineering, multiphysics analysis, COMSOL specialist
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Posted: 1 decade ago Dec 31, 2012, 1:19 p.m. EST
This is great news ! Can you tell us some more of the details ? What type of solver ? What settings on the solver ? Difference in settings between the versions or not ?

Thanks
This is great news ! Can you tell us some more of the details ? What type of solver ? What settings on the solver ? Difference in settings between the versions or not ? Thanks
Alexander Kuznetsov
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Posted: 1 decade ago Jan 2, 2013, 1:19 p.m. EST
I guess the default solver parameters might be different in 4.3a...

Did you open 4.2a model in 4.3a and run it without modification? Did you build the model 4.3a from scratch?
I guess the default solver parameters might be different in 4.3a... Did you open 4.2a model in 4.3a and run it without modification? Did you build the model 4.3a from scratch?
Sanket Kelkar
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Posted: 1 decade ago Sep 11, 2013, 11:50 a.m. EDT

Dear all,

I just want to share my recent experience with a convergence problem.

During last several weeks I was struggling with convergence problem. The model has two 2nd-order PDE and Electromagnetic Waves application modes coupled together. I was using 4.2a and 3.5a. (I thought there might not be big difference between 4.2a and 4.3a.) However neither secured convergence. After those painful time, I asked technical support (perhaps I should ask earlier...). The answer was so simple: use the latest version. And it works! I almost don't need to change anything. How long time I wasted...

The lesson is trust in newer version :)

Best
--
Pu, ZHANG ??
Departamento de Física Teórica de la Materia Condensada,
Universidad Autónoma de Madrid,
Madrid, Spain.


I have a different experience. My model ran perfectly in comsol 4.3 but is not running at all in 4.3 b. I think it has something to do with the geoemtry I am employing in the model but not sure yet. I am trying to create my model from scratch in the newer versions. But does anybody have any additional insight into this.

Regards,
Sanket
[QUOTE] Dear all, I just want to share my recent experience with a convergence problem. During last several weeks I was struggling with convergence problem. The model has two 2nd-order PDE and Electromagnetic Waves application modes coupled together. I was using 4.2a and 3.5a. (I thought there might not be big difference between 4.2a and 4.3a.) However neither secured convergence. After those painful time, I asked technical support (perhaps I should ask earlier...). The answer was so simple: use the latest version. And it works! I almost don't need to change anything. How long time I wasted... The lesson is trust in newer version :) Best -- Pu, ZHANG ?? Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, Madrid, Spain. [/QUOTE] I have a different experience. My model ran perfectly in comsol 4.3 but is not running at all in 4.3 b. I think it has something to do with the geoemtry I am employing in the model but not sure yet. I am trying to create my model from scratch in the newer versions. But does anybody have any additional insight into this. Regards, Sanket
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago Sep 11, 2013, 12:52 p.m. EDT
Dear Sanket,

I suspect it may have to do with the solver settings which change for specific types of problems. One example is the Double Dogleg solver introduced and made default for some contact problems starting I believe with v4.3. There are I am sure other similar solver changes. The new solver settings are generally better in my experience but that will never be the case for 100% of the problems. I suggest you expand the solver sub-nodes and compare them between the two COMSOL versions.

Nagi Elabbasi
Veryst Engineering
Dear Sanket, I suspect it may have to do with the solver settings which change for specific types of problems. One example is the Double Dogleg solver introduced and made default for some contact problems starting I believe with v4.3. There are I am sure other similar solver changes. The new solver settings are generally better in my experience but that will never be the case for 100% of the problems. I suggest you expand the solver sub-nodes and compare them between the two COMSOL versions. Nagi Elabbasi Veryst Engineering

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