[dune-pdelab] Dune reported error in newton.hh

[Markus Blatt]

Hey Jared,

On Fri, Jan 06, 2012 at 04:31:31PM +0100, Jared Okiro wrote:
> I have used the example DG code (Symmetric Weighted Interior Penalty
> Galerkin(SWIPG)) in pdelab/localoperator/convectiondiffusiondg.hh to
> solve a scalar nonlinear reaction-diffusion  equation and it worked
> well.
> I have extended the code to solve a two component  nonlinear
> reaction-diffusion system. However, at run time I get the error
> below: This error occurs when I evaluate the jacobian manually and
> also when I use numerical differentiation to determine the jacobian.
> 
> /Dune reported error: NewtonLinearSolverError [linearSolve:/homes/okiro/DUNE/dune-svn/dune-pdelab/dune/pdelab/backend/../newton/newton.hh:174]:
> NewtonSolver::linearSolve(): Linear solver did not converge in 1
> iterations./
> 

I would guess that the linear solver has real problems solving your
equation. As it tried only 1 step, I assume that it somehow broke
down.

> When I print the matrix of the system with the coarse mesh and few
> iterations, I see that the matrix assembled is for the initial
> condition for each of the children and this does not change with
> even slight more iterations. The matrix looks like this:
> 
> const residual [blocks=8,dimension=32]
> row    0   9.0e-01   9.0e-01   9.0e-01   9.0e-01
> row    4   9.0e-01   9.0e-01   9.0e-01   9.0e-01
> row    8   9.0e-01   9.0e-01   9.0e-01   9.0e-01
> row   12   9.0e-01   9.0e-01   9.0e-01   9.0e-01
> row   16   9.5e-01   9.5e-01   9.5e-01   9.5e-01
> row   20   9.5e-01   9.5e-01   9.5e-01   9.5e-01
> row   24   9.5e-01   9.5e-01   9.5e-01   9.5e-01
> row   28   9.5e-01   9.5e-01   9.5e-01   9.5e-01
> 

How did you print the matrix? It looks like it contains zero rows
(only each 4th row has nonzeros). Additionally the dimension 32x4
seems weired.

Markus

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