[petsc-users] Snes failled with reason -6

[Que Cat]

Barry,

It said that "No support for this operation for this object type! Matrix
format mpiaij does not have a built-in PETSc LU!".

I run it with option "-snes_monitor -ksp_monitor_true_residual
-snes_converged_reason -ksp_converged_reason." and received :
    0 SNES Function norm 1.414213647226e-01
    0 KSP preconditioned resid norm 8.424084241999e+08 true resid norm
1.414213647226e-01 ||r(i)||/||b|| 1.000000000000e+00
    1 KSP preconditioned resid norm 1.354908290122e-02 true resid norm
1.424694873074e-01 ||r(i)||/||b|| 1.007411345428e+00
Nonlinear solve did not converge due to DIVERGED_LINE_SEARCH iterations 0

It looks like that the preconditioned residual converges, but the true
residual does not.


On Fri, Dec 20, 2013 at 8:30 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
>   Run with
>
>    -snes_mf_operator -pc_type lu
>
>    I’m sorry I sent the wrong instructions before.
>
>    Barry
>
> On Dec 20, 2013, at 7:54 AM, Que Cat <quecat001 at gmail.com> wrote:
>
> > Hi Barry,
> >
> > Thanks for your exlanation. I used -snes_mf -pc_type lu and now it
> failed with reason -3 (/* the linear solve failed */). So, something is
> wrong with the function.
> >
> >
> > On Thu, Dec 19, 2013 at 5:01 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> >
> >   ratio is || A - Afd || /||A|| where |||| is the frobenus norm and
> difference is || A - Afd ||.
> >
> >   Try using -snes_mf -pc_type lu
> >
> >    This can often converge even if the A you provide is wrong, so if
> this convergence sine then likely the Jacobian is wrong.
> >
> >    It is also possible that the function evaluation has a bug.
> >
> > http://www.mcs.anl.gov/petsc/documentation/faq.html#newton
> >
> >
> >    Barry
> >
> >
> >
> > On Dec 19, 2013, at 4:26 PM, Que Cat <quecat001 at gmail.com> wrote:
> >
> > > Hello,
> > >
> > > I use SNES to solve the non linear coupled equations. I have checked
> the hand-coded jacobian with -snes_type test and received the result:
> > > Norm of matrix ratio 1.39606e-23 difference 1.53372e-14 (user-defined
> state)
> > > Norm of matrix ratio 3.03157e-10 difference 0.33305 (constant state
> -1.0)
> > > Norm of matrix ratio 3.03157e-10 difference 0.33305 (constant state
> 1.0)
> > > It said that "  if the ratio is O(1.e-8), the hand-coded Jacobian is
> probably correct." What is the second paramenter "difference 1.53372e-14
> ...."? Does it play any role in checking the accuracy of hand-coded
> jacobian?
> > >
> > > The SNES solver for failed with the reason -6 "the line search
> failed". I tried with all other line search method stated in the PETSC
> manual, but they all failed.
> > >
> > > I tried to figure out what is wrong with my code? Could you please
> give me any recommendation to direct me how to check my code? I appreciate
> your help.
> > >
> > > QUe
> > >
> >
> >
>
>
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