Variants of Newton Solver

Question

Hello,

I am wondering if FEniCS also provide a damped version or other variants of Newton's method?
When calling info(prm, True) for (NewtonSolver) parameters prm I found the options 'method' and 'relaxation_parameter'. Unfortunately I could not find any documentation on these parameters, how effect those the behaviour of the Newton Solver?

Thanks,

Elisa

Answer 1

In equation 7

Comments

Thank you very much for your answer.

Are there any extensions to Newton towards globally convergent methods such as trust-region methods? What about Quasi-Newton methods?

And I have another general question, is there any way to find out how I can set parameters? Most parameters have range [], how do I know what sensible choices are (besides looking how they were set in the tutorials and demos)?

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I think for more advanced nonlinear solvers your best bet it to go into the PETSc solver interface. It has a plethora of techniques which are documented on their site. I would recommend accessing them through the following commands:
eg:

PETScOptions.set('pc_type', 'asm') 
PETScOptions.set('sub_pc_type', 'lu')
PETScOptions.set('pc_asm_overlap', '10')

Some of the other snes options / keywords can be found here.

As for your second question, getting approximate values from examples is good because it can get you going quickly. If you want to fine-tune them though, you are going to have to read up on what they actually mean.

Good luck!