[petsc-users] Spatial distribution of the residual after an implicit TS timestep

[Mani Chandra]

Ahh thanks. I got confused cause
there apparently is indeed a function called SNESSetMonitor in a (very) old
version of petsc:
http://www.mcs.anl.gov/petsc/petsc-2.3.1/docs/manualpages/SNES/SNESSetMonitor.html


On Tue, Mar 18, 2014 at 11:11 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
>  Sorry
> http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/SNES/SNESMonitorSet.html
>
>
> On Mar 18, 2014, at 10:56 PM, Mani Chandra <mc0710 at gmail.com> wrote:
>
> > I can't find SNESSetMonitor in petsc-dev. I get the following error even
> after including petscsnes.h
> >
> > error: ‘SNESSetMonitor’ was not declared in this scope
> >
> > Moreover, there is no manpage for it on the petsc-dev SNES website:
> http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/SNES/index.html
> >
> > Has it been removed?
> >
> >
> > On Tue, Mar 18, 2014 at 9:11 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> >
> > On Mar 18, 2014, at 7:54 PM, Mani Chandra <mc0710 at gmail.com> wrote:
> >
> > > The residual of the system of equation that I feed into TS with
> TSSetIFunction. I have a system of equations and I want to probe where most
> of the residual is coming from. The reason is that after certain time of
> evolution, the initial residual at the beginning of each time step
> increases by orders of magnitude than what it used to be at the beginning
> of the time step at early times. For ex, say at t=200, the SNES norm at the
> beginning of a TS timestep with the theta method would be something like
> 1.0812 and at t = 300, it would be 2e5 at the beginning. SNES then has to
> work much harder to reach the abs norm levels and so I want to investigate
> what is happening.
> >
> >    So this is the initial residual in the nonlinear solve.
> -snes_monitor_residual works for plotting if it is 2d otherwise write your
> own custom SNES monitor routine and call TSGetSNES, SNESSetMonitor().
> >
> >    Barry
> >
> > >
> > >
> > > On Tue, Mar 18, 2014 at 7:48 PM, Jed Brown <jed at jedbrown.org> wrote:
> > > Mani Chandra <mc0710 at gmail.com> writes:
> > >
> > > > Is there anyway I can get the residual at the beginning of the time
> step? I
> > > > tried TSSetPreStage and TSSetPreStep but they didn't work. Setting
> > > > TSSetPreStage would crash the program even if there is nothing in the
> > > > routine that I set and TSSetPreStep would give me the residual at
> the end
> > > > of the previous time step. I want to take a look at the residual at
> the
> > > > beginning of the new time step before the nonlinear solver starts.
> > >
> > > Residual of what?  What are you going to do with it?
> > >
> >
> >
>
>
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