[petsc-users] Convergence Criteria?

[Barry Smith]

On Sep 20, 2011, at 10:47 PM, Alan Wei wrote:

> Dear Dr. Smith,
>     I figure out this problem. Actually, I made my own RHS, but I did not multiply them by the volume (dx*dy). 
>     However, I met another problem. All values calculated from this example are exactly opposite to values from my own code. I wonder if the RHS I input by ComputeRHS are the really RHS or -1.*RHS?

   We do not change the sign of the right hand side.

   Barry

> 
> thanks in advance,
> Alan
> 
> On Mon, Sep 19, 2011 at 8:43 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> 
> On Sep 19, 2011, at 6:25 PM, Alan Wei wrote:
> 
> > Dear folks,
> >     I hope you guys are having a nice day.
> >     I'm reading the /src/ksp/ksp/examples/tutorials/ex29.c.html and wonder how to set up the convergence criteria?
> 
>   -ksp_rtol 1.e-10 for example
> 
>   Run with -ksp_monitor_true_residual -ksp_converged_reason
> 
> 
> > Currently I use it as a poisson solver to solve a Poisson Equation with three direction Neumann BC's and one direction Diriechlet BC's. It seems very bad on it.
> 
>    Hmm, multigrid should likely converge well. Are you sure you've set the BC's correctly?
> 
>   Barry
> 
> >
> > thanks in advance,
> > Alan
> 
>