[petsc-users] help about my ts program

[Jed Brown]

On Fri, 2 Jul 2010 14:44:25 -0400, Xuan YU <xxy113 at psu.edu> wrote:
> 
> On Jul 2, 2010, at 2:21 PM, Jed Brown wrote:
> 
> > On Fri, 2 Jul 2010 14:08:14 -0400, Xuan YU <xxy113 at psu.edu> wrote:
> >> If I don't provide Jacobian, it will be:  type: euler
> >>                   						  total number of nonlinear solver  
> >> iterations=0
> >> 								  total number of linear solver iterations=0
> >
> > The default TS is the simplest possible integrator, forward Euler.  Of
> > course this doesn't do any solves (no SNES) and is not appropriate for
> > stiff systems.  Run with -ts_type theta for something more likely to
> > work (and which will use SNES).
> >
> >> [0]PETSC ERROR: Floating point exception!
> >> [0]PETSC ERROR: User provided compute function generated a Not-a- 
> >> Number!
> >
> > Euler is unstable for your problem, this should have nothing to do  
> > with
> > the way you specified the Jacobian.
> >
> 
> 
> I tried beuler and pseudo, and I got the errors:

If you have petsc-dev, run in a debugger with -fp_trap to see where the
NaN is first computed.  Some possibilities include domain error (like
negative density), nonlinear instability, and inadequate solution of the
linear system.

Jed