[petsc-users] TimeStepper norm problems. EMIL Please read this

[Emil Constantinescu]

Hi Andrew - we found a bug in TSComputeRHSFunctionLinear.

In your code you need to provide the context to TSSetRHSFunction:
TSSetRHSFunction( tss, NULL, TSComputeRHSFunctionLinear, &c );

For now you can check out a branch that has implemented the fix by 
running git checkout emil/fix-ts-dae-rebased-v2 and then make everything.

The fix is at 
https://bitbucket.org/petsc/petsc/commits/557d2b190687a728e86290bdc604ce0d2dc53473

This is working for us.

We'll push the fix soon in master.

Emil

-- 
Emil M. Constantinescu, Ph.D.
Computational Mathematician
Argonne National Laboratory
Mathematics and Computer Science Division
9700 S Cass Avenue,
Argonne, IL 60439, USA

Ph: 630-252-0926
http://www.mcs.anl.gov/~emconsta

On 3/30/15 9:32 PM, Andrew Spott wrote:
> I’m sorry, I didn’t want to imply you were taking too much time.  I was
> just interested in trying to solve the problem myself, especially if it
> was a simpler fix.
>
> I don’t have enough of an understanding of the internals of PETSc
> though, if it depends on the compiler flags.
>
> Good luck!
>
> -Andrew
>
> —
> Andrew
>
>
> On Mon, Mar 30, 2015 at 7:23 PM, Emil Constantinescu
> <emconsta at mcs.anl.gov <mailto:emconsta at mcs.anl.gov>> wrote:
>
>     Hi Andrew,
>
>     Sorry for the delay; things are going slower with me over the spring
>     break but we are working on it.
>
>     The problem that you see may not be related to the integrator, which
>     runs well (we get expected convergence rates and good results) for
>     other
>     problems, in particular, for problems with real variables (and no
>     c++11). So the high level th->endpoint implementation seems fine.
>
>     For some reason the linear solver is misbehaving when using cn. If you
>     use option -snes_mf the problem disappears.
>
>     Please do not use -ts_theta_adapt until it is fixed.
>
>     In conclusion I don't think that looking at theta.c will be productive.
>     We are currently looking at what happens at the lower levels.
>
>     Thanks,
>     Emil
>
>     On 3/30/15 4:25 PM, Andrew Spott wrote:
>      > Emil: If I want to fix this myself, do you have any idea where I
>     should
>      > start looking? I assume in the th->endpoint section of
>     TSStep_Theta in
>      >
>     http://www.mcs.anl.gov/petsc/petsc-current/src/ts/impls/implicit/theta/theta.c.html?
>
>      >
>      > Thanks,
>      >
>      > -Andrew
>      >
>      >
>      >
>
>