[petsc-users] Convergence Criteria?

[Alan Wei]

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?

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
>
>
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