[petsc-users] Snes failled with reason -6

[Anton Popov]

On 12/20/13 3:40 PM, Que Cat wrote:
> Barry,
>
> It said that "No support for this operation for this object type! 
> Matrix format mpiaij does not have a built-in PETSc LU!".
Try with -pc_factor_mat_solver_package mumps (superlu_dist)

If you didn't install them reconfigure with:

--download-scalapack=1
--download-mumps=1

or:

--download-superlu_dist=1

Or just run sequentially

Anton
>
> 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 
> <mailto: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
>     <mailto: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
>     <mailto: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
>     <mailto: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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