[petsc-users] RK substeps

[Juha Jäykkä]

> We pass in the time of the stage when your RHSFunction is called. If you

Right, how can I have missed that?!? Thanks.

> haven't eliminated boundary conditions, your system is likely
> differential-algebraic, in which case you can use the IFunction interface

Eliminated? I am not sure what you mean. My boundaries are "periodic", but 
thanks to the nature of my problem, they are periodic only up to a gauge 
transformation. I need to perform that gauge transform at each time step.

I would be more than happy not to have to do that, but I cannot really see a 
way out of it, so, if you have any ideas, I am very interested in hearing 
them.

> improved in petsc-dev, so consider using it if you want the latest

Thanks for the tip, but I am stuck at 3.1 because I need TAO, too and it still 
does not support 3.2.

Cheers,
Juha