[petsc-users] KSP_DIVERGED_NAN

[Barry Smith]

  First run with -pc_type lu what happens? Then run small problems with -mat_view and see if the matrix entries look reasonable, also check that the right hand side vector entries look reasonable. 

   Barry

On Oct 13, 2011, at 3:04 AM, Marco Cisternino wrote:

> Hi to everybody,
> I wrote an interface elliptic problem solver in 2D and 3D. The linear system I assemble depends on the geometrical characteristics of a level set function. I tested them with several and more and more complex interfaces, but now I would try it with a real 3D interface. But I probably have some problem with the computation of a good level set function, maybe the cause is the low resolution of the original interface. The evidence of my problem is in the subject. No matter what iterative petsc solver I try to use the run stops at the first iteration with a Nan residual. I don't want to ask you to understand the problem, but to give me some information about how to debug I situation like this. The interface is too complex to be deeply checked, then I hope that looking how the ksp yields a nan residual could help me.
> Thank you so much.
> 
> Best regards,
> 
>    Marco
> 
> -- 
> Marco Cisternino
> PhD Student
> Politecnico di Torino
> Mobile:+393281189696
> Email:marco.cisternino at polito.it
>