[petsc-users] SNES norm control

[Gideon Simpson]

That seems to to allow for me to cook up a convergence test in terms of the 2 norm.  What I’m really looking for is the ability to change things to be something like the 2 norm of the vector with elements

F_i/|x_i|

where I am looking for a root of F(x).  I can just build that scaling into the form function, but is there a way to do it without rewriting that piece of the code?


-gideon

> On Jan 12, 2016, at 12:14 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> 
> 
>   You can use SNESSetConvergenceTest() to use whatever test you want to decide on convergence.
> 
> Barry
> 
>> On Jan 11, 2016, at 3:26 PM, Gideon Simpson <gideon.simpson at gmail.com> wrote:
>> 
>> I’m solving nonlinear problem for a complex valued function which is decomposed into real and imaginary parts, Q = u + i v.  What I’m finding is that where |Q| is small, the numerical phase errors tend to be larger.  I suspect this is because it’s using the 2-norm for convergence in the SNES, so, where the solution is already, the phase errors are seen as small too.  Is there a way to use something more like an infinity norm with SNES, to get more point wise control?
>> 
>> -gideon
>> 
> 

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