[petsc-users] TS tutorial ex11 in Fortran

Matthew Knepley knepley at gmail.com
Sun Dec 13 08:52:31 CST 2020 

On Sun, Dec 13, 2020 at 9:35 AM Thibault Bridel-Bertomeu <
thibault.bridelbertomeu at gmail.com> wrote:

> Hello Matthew,
>
> Thank you for your answer and the pointer to SNESSetFunction(). Is the
> PETSC_F90_2PTR_PROTO(ptr) necessary for every wrapper of that category ?
>
> So far, for the PetscDSSetRiemannSolver, I did this :
>
> #ifdef PETSC_HAVE_FORTRAN_CAPS
> #define petscdssetriemannsolver_ PETSCDSSETRIEMANNSOLVER
> #elif !defined(PETSC_HAVE_FORTRAN_UNDERSCORE) &&
> !defined(FORTRANDOUBLEUNDERSCORE)
> #define petscdssetriemannsolver_ petscdssetriemannsolver
> #endif
>
> PetscFortranCallbackId riemannsolver;
>
> static PetscErrorCode ourriemannsolver(PetscInt dim, PetscInt Nf,
> PetscReal x[], PetscReal n[], PetscScalar uL[], PetscScalar uR[], PetscInt
> numConstants, PetscScalar constants[], PetscScalar flux[], void *ctx)
> {
>     PetscObjectUseFortranCallback((PetscDS)ctx, riemannsolver, (PetscInt*,
> PetscInt*, PetscReal*, PetscReal*, PetscScalar*, PetscScalar*, PetscInt*,
> PetscScalar*, PetscScalar*, void*, PetscErrorCode*),
>                                   (&dim, &Nf, x, n, uL, uR, &numConstants,
> constants, flux, _ctx, &ierr));
> }
>
> PETSC_EXTERN void petscdssetriemannsolver_(PetscDS *prob, PetscInt *f,
>                                            void (*rs)(PetscInt *dim,
> PetscInt *Nf, PetscReal x[], PetscReal n[], PetscScalar uL[], PetscScalar
> uR[], PetscInt *numConstants, PetscScalar constants[], PetscScalar flux[],
> void *ctx, PetscErrorCode *jerr),
>                                            PetscErrorCode *ierr)
> {
>     *ierr = PetscObjectSetFortranCallback((PetscObject)*prob,
> PETSC_FORTRAN_CALLBACK_CLASS, &riemannsolver, (PetscVoidFunction)rs, prob);
>     *ierr = PetscDSSetRiemannSolver(*prob, *f, (void*)ourriemannsolver);
> }
>
> It compiles, but I have no idea whether it works or not, and I won't have
> until the program is entirely built (with the TS and all) and it actually
> has to call a Riemann solver added with that routine.
> What do you think ?
>

It looks good for right now. We can help you debug it when the rest of the
wrappers are in place.

  Thanks,

     Matt


> Thibault
>
> Le dim. 13 déc. 2020 à 15:29, Matthew Knepley <knepley at gmail.com> a
> écrit :
>
>> On Sun, Dec 13, 2020 at 9:17 AM Mark Adams <mfadams at lbl.gov> wrote:
>>
>>> I don't think function pointers to PETSc (DS and DM) methods are not
>>> going to work in Fortran:
>>>
>>>   ierr = PetscDSAddBoundary(prob, DM_BC_NATURAL_RIEMANN, "inflow",
>>>  "Face Sets", 0, 0, NULL, (void (*)(void)) PhysicsBoundary_Advect_Inflow,
>>> NULL,  ALEN(inflowids),  inflowids,  phys);CHKERRQ(ierr);
>>>
>>> You could write a funcs.c file that you call from your fortran code,
>>> like, call setBC1(prob,...,ierr)
>>>
>>> and put PhysicsBoundary_Advect_Inflow and setBC1 in funcs.c, for
>>> instance.
>>>
>>
>> Wrappers for functions that that function arguments are possible, but
>> more involved. We have to create an internal struct that
>> holds Fortran function pointers, and then call them with the right
>> arguments. This has been done for SNESSetFunction() for
>> instance, so we would start emulating that.
>>
>>   Thanks,
>>
>>       Matt
>>
>>
>>>
>>> On Sun, Dec 13, 2020 at 5:32 AM Thibault Bridel-Bertomeu <
>>> thibault.bridelbertomeu at gmail.com> wrote:
>>>
>>>> Good morning all,
>>>>
>>>> Thank you Barry for your answer.
>>>> I started adding some interfaces (PetscFVSetComponentName, PetscFVView
>>>> & PetscFVSetType so far) and I have to say I think it is working quite
>>>> well, but the prototypes of those functions are still quite "simple".
>>>> I am stuck at how to implement the wrappers for PetscDSSetRiemannSolver
>>>> and PetscDSSetContext though, especially on how to pass a function as an
>>>> argument to PetscDSSetRiemannSolver ... Are there any similar functions
>>>> that may already have their wrappers ?
>>>>
>>>> Thank you very much,
>>>>
>>>> Thibault
>>>>
>>>>
>>>> Le sam. 12 déc. 2020 à 23:28, Barry Smith <bsmith at petsc.dev> a écrit :
>>>>
>>>>>
>>>>>
>>>>> On Dec 12, 2020, at 2:59 PM, Thibault Bridel-Bertomeu <
>>>>> thibault.bridelbertomeu at gmail.com> wrote:
>>>>>
>>>>> Dear Jed, dear Barry,
>>>>>
>>>>> Thank you for the fast answers !
>>>>>
>>>>> If I have any success I will make sure to make a pull request to
>>>>> provide some version of ex11 in Fortran.
>>>>>
>>>>> Regarding the stubs, I admit I started looking in that direction to
>>>>> add the missing wrappers but I am not sure I fully understand the process
>>>>> yet.
>>>>> For each C function, I gotta provide a Fortran interface in a .h90
>>>>> file as well as a C function that has a Fortran-like prototype and calls
>>>>> the C function - right ?
>>>>>
>>>>>
>>>>>   Yes,
>>>>>
>>>>> However there are a few things I could not find / understand yet.
>>>>> For instance, it appears that for C functions that have character
>>>>> string arguments take an extra argument in their
>>>>> Fortran-like-prototype-wrapper, namely the length of the string. Is that
>>>>> passed automatically ? I couldn’t find where it could come from ...
>>>>>
>>>>>
>>>>>    This secret argument is put automatically by the Fortran compiler.
>>>>>
>>>>> Another thing is for functions like PetscFVView. I guess the wrapping
>>>>> is less straightforward because I tried a quick something and it
>>>>> segfault’ed. I couldnt find the wrapper for DMView although there is such a
>>>>> routine in Fortran too. Could you please detail how to wrap such functions
>>>>> ?
>>>>>
>>>>>
>>>>> PETSC_EXTERN void dmview_(DM *da,PetscViewer *vin,PetscErrorCode *ierr)
>>>>> {
>>>>>   PetscViewer v;
>>>>>   PetscPatchDefaultViewers_Fortran(vin,v);
>>>>>   *ierr = DMView(*da,v);
>>>>> }
>>>>>
>>>>> dm/interface/ftn-custom/zdmf.c
>>>>>
>>>>>
>>>>>
>>>>> Thank you very much again,
>>>>>
>>>>> Thibault Bridel-Bertomeu
>>>>>
>>>>> Le sam. 12 déc. 2020 à 21:48, Barry Smith <bsmith at petsc.dev> a écrit :
>>>>>
>>>>>>
>>>>>>    PETSc Fortran interfaces are a combination of automatically
>>>>>> generated and manually generated.
>>>>>>
>>>>>>    For any C PETSc function if the manual page begins with /*@  it
>>>>>> generates the Fortran interface automatically (make allfortranstubs).  If
>>>>>> it begins /*@C then either the Fortran interface is done manually or is
>>>>>> missing.
>>>>>>
>>>>>>    C functions that have character string arguments or function
>>>>>> arguments (or a few other special cases) need to be manually provided.  The
>>>>>> automatically generated stubs go in the directory ftn-auto while manually
>>>>>> generated ones go in the directory fin-custom.
>>>>>>
>>>>>>    Perhaps you could first generate a list of "missing" Fortran stubs
>>>>>> and then for each stub determine why it is missing and if it can be
>>>>>> provided. Some are likely easy to provide but a few (involving function
>>>>>> arguments) will be more involved. Once you have all the stubs available
>>>>>> translating ex11.c becomes straightforward.
>>>>>>
>>>>>>   Barry
>>>>>>
>>>>>>
>>>>>> On Dec 12, 2020, at 9:30 AM, Thibault Bridel-Bertomeu <
>>>>>> thibault.bridelbertomeu at gmail.com> wrote:
>>>>>>
>>>>>> Dear all,
>>>>>>
>>>>>> Is there somewhere a version of the TS tutorial ex11.c in Fortran ?
>>>>>> I am looking into building in F90 (let's say that it is an
>>>>>> unavoidable constraint) an unstructured 3D solver of the Euler equations
>>>>>> using the "new" features of PETSc - mostly DMPlex & PetscFV - but I think
>>>>>> there are some interfaces missing and I find it hard to find workarounds in
>>>>>> Fortran. I would be grateful if anyone could please give me some pointers
>>>>>> ...
>>>>>>
>>>>>> Thank you very much in advance,
>>>>>>
>>>>>> Thibault Bridel-Bertomeu
>>>>>> —
>>>>>> Eng, MSc, PhD
>>>>>> Research Engineer
>>>>>> CEA/CESTA
>>>>>> 33114 LE BARP
>>>>>> Tel.: (+33)557046924
>>>>>> Mob.: (+33)611025322
>>>>>> Mail: thibault.bridelbertomeu at gmail.com
>>>>>>
>>>>>>
>>>>>> --
>>>>> Thibault Bridel-Bertomeu
>>>>> —
>>>>> Eng, MSc, PhD
>>>>> Research Engineer
>>>>> CEA/CESTA
>>>>> 33114 LE BARP
>>>>> Tel.: (+33)557046924
>>>>> Mob.: (+33)611025322
>>>>> Mail: thibault.bridelbertomeu at gmail.com
>>>>>
>>>>>
>>>>>
>>
>> --
>> 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.cse.buffalo.edu/~knepley/>
>>
>

-- 
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.cse.buffalo.edu/~knepley/>
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