[petsc-users] Inquiry about metric-based adaptation using MMG in petsc

[neil liu]

Thanks a lot, Jed.
I traced  the code and found the following issues,
1) in *PetscErrorCode DMPlexMetricNormalize(DM dm, Vec metricIn, PetscBool
restrictSizes, PetscBool restrictAnisotropy, Vec metricOut, Vec
determinant),*
the metricIn is zero
*. And this seems not reasonable. *
*Go back to,*
2) DMAdaptorAdapt_Sequence_Private(DMAdaptor adaptor, Vec inx, PetscBool
doSolve, DM *adm, Vec *ax)
with -sol_adapt_loc_pre_view, -adapt_gradient_view and -adapt_hessian_view,
all these three vectors are zero.
This is not reasonable.

*Go back to, *
*3) *PetscErrorCode DMAdaptorAdapt(DMAdaptor adaptor, Vec x,
DMAdaptationStrategy strategy, DM *adm, Vec *ax)
    x is zero here.
Go back to,
*4)  *PetscCall(SNESSolve(snes, NULL, u));
The initial guess u is zero. It seems this is the reason. A little weird.
An intiial guess with zero should be resonable.

It seems maybe something is not reasonable for the logic in
*DMPlexMetricNormalize.*

*Thanks,*


*Xiaodong *







On Fri, Sep 13, 2024 at 2:22 PM Jed Brown <jed at jedbrown.org> wrote:

> This error message is coming from the following:
>
> $ rg -B4 'Global metric normalization factor must be in'
> src/dm/impls/plex/plexmetric.c
> 1308-    PetscCall(PetscDSSetObjective(ds, 0, detMFunc));
> 1309-    PetscCall(DMPlexComputeIntegralFEM(dmDet, determinant, &integral,
> NULL));
> 1310-  }
> 1311-  realIntegral = PetscRealPart(integral);
> 1312:  PetscCheck(realIntegral > 1.0e-30, PETSC_COMM_SELF,
> PETSC_ERR_ARG_OUTOFRANGE, "Global metric normalization factor must be in
> (0, inf). Is the input metric positive-definite?");
>
> Perhaps you can independently check what integrand is being provided. It's
> probably zero or negative. You could apply this patch so the error message
> will report a value.
>
>
> diff --git i/src/dm/impls/plex/plexmetric.c
> w/src/dm/impls/plex/plexmetric.c
> index 61caeed28de..906cb394027 100644
> --- i/src/dm/impls/plex/plexmetric.c
> +++ w/src/dm/impls/plex/plexmetric.c
> @@ -1309,7 +1309,7 @@ PetscErrorCode DMPlexMetricNormalize(DM dm, Vec
> metricIn, PetscBool restrictSize
>      PetscCall(DMPlexComputeIntegralFEM(dmDet, determinant, &integral,
> NULL));
>    }
>    realIntegral = PetscRealPart(integral);
> -  PetscCheck(realIntegral > 1.0e-30, PETSC_COMM_SELF,
> PETSC_ERR_ARG_OUTOFRANGE, "Global metric normalization factor must be in
> (0, inf). Is the input metric positive-definite?");
> +  PetscCheck(realIntegral > 1.0e-30, PETSC_COMM_SELF,
> PETSC_ERR_ARG_OUTOFRANGE, "Global metric normalization factor %g must be in
> (0, inf). Is the input metric positive-definite?", (double)realIntegral);
>    factGlob = PetscPowReal(target / realIntegral, 2.0 / dim);
>
>    /* Apply local scaling */
>
>
> neil liu <liufield at gmail.com> writes:
>
> > Dear Petsc developers and users,
> >
> > I am  trying to explore adaptive mesh refinement (tetradedra) with Petsc.
> > It seems case 12 ($PETSC DIR/src/snes/tutorials/ex12.c, from paper,
> >
> https://urldefense.us/v3/__https://arxiv.org/pdf/2201.02806__;!!G_uCfscf7eWS!ZEwaHkvYc_IrjycFr8LiNi-nZcFqu0ZpsydAAomxptQ6C0xkBs3qhn5ba31Z4vipKf4mTrqDm8A5S65DDD_xFg$
> ) is a good example.
> > However when I tried,
> > ./ex12 -run_type full -dm_plex_dim 3 -dm_distribute -dm_plex_box_faces
> > 10,10,10 -bc_type dirichlet -petscspace_degree 1 -variable_coefficient
> ball
> > -snes_converged
> > _reason ::ascii_info_detail -ksp_type cg -pc_type sor
> -snes_adapt_sequence
> > 3 -adaptor_target_num 1000 -dm_plex_metric_h_max  0.5  -dm_adaptor mmg
> >       L_2 Error: 1.55486
> >       Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE
> iterations 2
> >
> > it shows the following error,
> > [0]PETSC ERROR: --------------------- Error Message
> > --------------------------------------------------------------
> > [0]PETSC ERROR: Argument out of range
> > [0]PETSC ERROR: Global metric normalization factor must be in (0, inf).
> Is
> > the input metric positive-definite?
> >
> > Do  you have any suggestions here?
> >
> > Thanks,
> >
> > Xiaodong
>
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