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maxm no. of newton's iterations reached & parametric solver

Posted Jan 2, 2011, 12:35 a.m. EST Studies & Solvers Version 4.1, Version 5.1 10 Replies

Sirisha Govindaraju
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Question about newton's iterations:

I keep getting the following error

Failed to find a solution.
Maximum number of Newton iterations reached.
Returned solution has not converged.

I am unable to locate where the solver is pulling up these Newton's iterations from. Can someone please guide me where to find the number for Newton's iteration? Also, any insight about why I am getting this error will also be very helpful.
----------------------------------------------------

Question about parametric solver:
I am wondering if there are any tutorials/examples that show me how to use the parametric solver. I am trying to use it along with a stationary solver because I am having convergence issues but I am not sure how to use it. For my problem when I choose to use the default solver, I get the iterative solver. So I am a little confused about how the parametric solver works. Should I be using it along with the iterative solver?

Thanks for the help.

Sirisha

PS: Happy New year to all!
10 Replies Last Post Apr 29, 2016, 2:19 a.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 2, 2011, 2:59 a.m. EST
Hi

check the doc, by a quick search I find in v4.1 p220 ch4 Solver Features Comsol Multiphysics Reference Guide pdf:

Further options that apply to one or several selections (as indicated at each bullet) made in the Termination technique list are:
• Maximum number of iterations (only available when Termination technique is set to Tolerance). Use this edit field to limit the number of Newton iterations. When the maximum number of iterations have been performed Newton’s method is terminated even if the tolerance is not fulfilled.

Anyhow if you hit this error its eiterh that the derivative isnot well defined, or that your initial condition (defaults = 0) are too far from a good guess. Perhaps a stationary solving and store + restart from there could help


--
Good luck
Ivar
Hi check the doc, by a quick search I find in v4.1 p220 ch4 Solver Features Comsol Multiphysics Reference Guide pdf: Further options that apply to one or several selections (as indicated at each bullet) made in the Termination technique list are: • Maximum number of iterations (only available when Termination technique is set to Tolerance). Use this edit field to limit the number of Newton iterations. When the maximum number of iterations have been performed Newton’s method is terminated even if the tolerance is not fulfilled. Anyhow if you hit this error its eiterh that the derivative isnot well defined, or that your initial condition (defaults = 0) are too far from a good guess. Perhaps a stationary solving and store + restart from there could help -- Good luck Ivar
Sirisha Govindaraju
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Posted: 1 decade ago Jan 3, 2011, 3:10 p.m. EST
Thanks Ivar! One more question about the newton's iterations: When I set the iterations to 5000, how is that the GMRES iteration value is showing 5870 and the solver is still running? Where is the solver getting this value from?

I am using a stationary solver and my problem uses a iterative/multigrid solver (that was the default option) and I see three lines in my progress window:
nonlinear solver
GMRES
Assembly

Nonlinear solver is showing parameter =step and value =547 .What does this mean?
GMRES is showing parameter = iteration & value =5870. What does this mean?

Thanks!
Sirisha
Thanks Ivar! One more question about the newton's iterations: When I set the iterations to 5000, how is that the GMRES iteration value is showing 5870 and the solver is still running? Where is the solver getting this value from? I am using a stationary solver and my problem uses a iterative/multigrid solver (that was the default option) and I see three lines in my progress window: nonlinear solver GMRES Assembly Nonlinear solver is showing parameter =step and value =547 .What does this mean? GMRES is showing parameter = iteration & value =5870. What does this mean? Thanks! Sirisha
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 4, 2011, 3:53 a.m. EST
Hi

there aou are asking more than what I can answer in detail, because I'm not enough familiar with those solver internals, those are the type of questions I send myself to "support" or I ask the COMSOl experts during the courses or at hte yearly Conference ;)

--
Good luck
Ivar
Hi there aou are asking more than what I can answer in detail, because I'm not enough familiar with those solver internals, those are the type of questions I send myself to "support" or I ask the COMSOl experts during the courses or at hte yearly Conference ;) -- Good luck Ivar
Sirisha Govindaraju
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Posted: 1 decade ago Jan 4, 2011, 11:26 a.m. EST
Ivar,

:)
I don't know if you are a COMSOL user like me or if you are a part of the COMSOL tester/developer team. But thanks for the help! I will check with the support team.

Sirisha

Ivar, :) I don't know if you are a COMSOL user like me or if you are a part of the COMSOL tester/developer team. But thanks for the help! I will check with the support team. Sirisha
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 4, 2011, 12:49 p.m. EST
Hi

I'm a standard Comsol user as pobably yourself, no link to COMSOL, apart that I reaally like their tool, the only difference, with others is that I believe in exchange to learn for you and for me ;)

--
Good luck
Ivar
Hi I'm a standard Comsol user as pobably yourself, no link to COMSOL, apart that I reaally like their tool, the only difference, with others is that I believe in exchange to learn for you and for me ;) -- Good luck Ivar
Ehsan Momeni
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Posted: 1 decade ago Jan 9, 2012, 4:30 a.m. EST
dear sir
your speaking and guideness is so help ful for me thank u
most of the time if ,i have a problem, i search in your webs about the other's problem and just do your guidness
dear sir your speaking and guideness is so help ful for me thank u most of the time if ,i have a problem, i search in your webs about the other's problem and just do your guidness
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 9, 2012, 4:59 a.m. EST
Hi

That's good that it helps
But you could also try to answer others question, the goal is that everyone helps everyone,
I cannot answer everything anyhow ;)

--
Good luck
Ivar
Hi That's good that it helps But you could also try to answer others question, the goal is that everyone helps everyone, I cannot answer everything anyhow ;) -- Good luck Ivar
Nitesh Rawat
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Posted: 1 decade ago Jun 11, 2012, 5:44 a.m. EDT
hey did you get rid off the above error.
I am also encountering with the same problem.
i would be grateful, if you could help me out.
hey did you get rid off the above error. I am also encountering with the same problem. i would be grateful, if you could help me out.
Alex Zhang
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Posted: 9 years ago Oct 30, 2015, 5:15 p.m. EDT
The default iteration step is 25 for steady study.

This error means within this 25 iterations, the remaining error is bigger than 10^-3. That is not a big deal. Just change 25 to maybe 100.

Problem solved.
The default iteration step is 25 for steady study. This error means within this 25 iterations, the remaining error is bigger than 10^-3. That is not a big deal. Just change 25 to maybe 100. Problem solved.
Aarti Arora
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Posted: 9 years ago Apr 29, 2016, 2:19 a.m. EDT
Dear Sir
Thanku very much for your valuable Guidance. I got my problem solved.
Dear Sir Thanku very much for your valuable Guidance. I got my problem solved.

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