[petsc-users] PetscFEIntegrateBdResidual_Basic

[David Fuentes]

Sorry, If I call this AddBoundary Twice with different markers/ids, the
bcFunc seems to be applied to set values for DM_BC_ESSENTIAL not
DM_BC_NATURAL?

Can I call    ierr = PetscDSSetBdResidual(prob, 0, f0_bd_u, f1_bd_zero)
twice to set the f0 functions different for each boundary ?


/*@C
  PetscDSAddBoundary - Add a boundary condition to the model

  Input Parameters:
+ ds          - The PetscDS object
. type        - The type of condition, e.g.
DM_BC_ESSENTIAL/DM_BC_ESSENTIAL_FIELD (Dirichlet), or DM_BC_NATURAL
(Neumann)
. name        - The BC name
. labelname   - The label defining constrained points
. field       - The field to constrain
. numcomps    - The number of constrained field components
. comps       - An array of constrained component numbers
. bcFunc      - A pointwise function giving boundary values
. numids      - The number of DMLabel ids for constrained points
. ids         - An array of ids for constrained points
- ctx         - An optional user context for bcFunc

  Options Database Keys:
+ -bc_<boundary name> <num> - Overrides the boundary ids
- -bc_<boundary name>_comp <num> - Overrides the boundary components

  Level: developer

.seealso: PetscDSGetBoundary()
@*/

On Mon, Nov 20, 2017 at 11:33 AM, David Fuentes <fuentesdt at gmail.com> wrote:

> Thanks! will give that a try!
> df
>
> On Mon, Nov 20, 2017 at 11:23 AM, Matthew Knepley <knepley at gmail.com>
> wrote:
>
>> On Mon, Nov 20, 2017 at 12:20 PM, David Fuentes <fuentesdt at gmail.com>
>> wrote:
>>
>>> Thanks for the quick reply. Indeed it does work like this. I have added
>>> a location dependence on the boundary to differentiate the two. However,
>>> when my mesh moves then the BC will be applied incorrectly.
>>>
>>
>> I don't think you should have to do that. You can call AddBoundary twice.
>> Once with a function with the first branch and marker value 3, and the next
>> with the second branch and marker value 2. Does
>> that make sense?
>>
>>   Thanks,
>>
>>      Matt
>>
>>> *//  PetscFEIntegrateBdResidual_Basic DMPlexComputeBdResidual_Internal*
>>>
>>> *static* *void** f0_bd_u(PetscInt dim, PetscInt Nf, PetscInt NfAux,*
>>>
>>>                     *const** PetscInt uOff[], **const** PetscInt
>>> uOff_x[], **const** PetscScalar u[], **const** PetscScalar u_t[], *
>>> *const** PetscScalar u_x[],*
>>>
>>>                     *const** PetscInt aOff[], **const** PetscInt
>>> aOff_x[], **const** PetscScalar a[], **const** PetscScalar a_t[], *
>>> *const** PetscScalar a_x[],*
>>>
>>> *                    PetscReal t, **const** PetscReal x[], **const**
>>> PetscReal n[], PetscInt numConstants, **const** PetscScalar
>>> constants[], PetscScalar f0[])*
>>>
>>> *{ *
>>>
>>> *  PetscInt d;*
>>>
>>>   *double** radius = **0.0**;*
>>>
>>>   *const* *double**  zthresh = (**3.** - **4.5**/**2.**)***.01**; **//
>>> [m]*
>>>
>>>   *for** (d = **0**; d < **2**; ++d) radius += x[d]*x[d];*
>>>
>>> *  radius = sqrt(radius); *
>>>
>>>   *if** ( radius > **.001**/**2.**  ) *
>>>
>>> *    {f0[**0**] =  constants[**2**] * u[**0**];}*
>>>
>>>   *else*
>>>
>>> *    {*
>>>
>>> *     f0[**0**] = -constants[**3**]       ; *
>>>
>>> *    }*
>>>
>>> *} *
>>>
>>>
>>> On Mon, Nov 20, 2017 at 11:02 AM, Matthew Knepley <knepley at gmail.com>
>>> wrote:
>>>
>>>> On Mon, Nov 20, 2017 at 11:46 AM, David Fuentes <fuentesdt at gmail.com>
>>>> wrote:
>>>>
>>>>> *Is there a way to pass the boundary set id to the function pointers
>>>>> for the residual evaluation on the boundary ?*
>>>>>
>>>>> *https://bitbucket.org/petsc/petsc/src/d89bd21cf2b5366df29efb6006298d2bc22fb509/src/dm/dt/interface/dtfe.c?at=master&fileviewer=file-view-default#dtfe.c-4245
>>>>> <https://bitbucket.org/petsc/petsc/src/d89bd21cf2b5366df29efb6006298d2bc22fb509/src/dm/dt/interface/dtfe.c?at=master&fileviewer=file-view-default#dtfe.c-4245>*
>>>>>
>>>>> *I want to pass the boundary condition/constraint ID (ids):
>>>>> PetscErrorCode PetscDSAddBoundary(PetscDS ds, DMBoundaryConditionType type,
>>>>> const char name[], const char labelname[], PetscInt field, PetscInt
>>>>> numcomps, const PetscInt *comps, void (*bcFunc)(void), PetscInt numids,
>>>>> const PetscInt *ids, void *ctx)*
>>>>>
>>>>> *to the functions for the residual evaluation on the boundary.*
>>>>>
>>>>>
>>>>> *For example, I have two side sets in an exodus file. I want to
>>>>> implement Neumann boundary conditions on side set = 2 and Mixed/Cauchy BC
>>>>> on side set = 3. Or similarly use different*
>>>>>
>>>>> *gmsh BC tags for Neumann/Mixed BC.*
>>>>>
>>>> I am not completely against this, but let me respond with my rationale
>>>> first. What I thought you would do, is call AddBoundary() twice. Once with
>>>> the
>>>> Neumann function and value 2, and once with the Cauchy function and
>>>> value 3. Does that not work in your situation?
>>>>
>>>> Also, I am refectoring this right now because a DS object can only take
>>>> a single boundary integral point function (which is a pain for
>>>> inhomogeneous Neumann),
>>>> so I welcome input.
>>>>
>>>>   Thanks,
>>>>
>>>>     Matt
>>>>
>>>> --
>>>> What most experimenters take for granted before they begin their
>>>> experiments is infinitely more interesting than any results to which their
>>>> experiments lead.
>>>> -- Norbert Wiener
>>>>
>>>> https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>
>>>>
>>>
>>>
>>
>>
>> --
>> What most experimenters take for granted before they begin their
>> experiments is infinitely more interesting than any results to which their
>> experiments lead.
>> -- Norbert Wiener
>>
>> https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>
>>
>
>
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