[petsc-dev] Julia Petsc Wrapper

[Matthew Knepley]

On Tue, Jul 14, 2015 at 8:03 PM, Jared Crean <jcrean01 at gmail.com> wrote:

>      Hello,
>         PETSC_USE_COMPLEX isn't a symbol in the shared library when Petsc
> is built with complex scalars, so I don't see a way to access it at
> runtime. I'll have to write a simple C program that uses sizeof() and write
> the value to a file.
>

That is crazy. How about

  isComplex = PETSC_COMPLEX == PETSC_SCALAR

   Matt


>         As for the MPI communicator, the julia MPI package uses a C int to
> store it, so I will typealias to that to ensure consistency.  If an MPI
> implementation uses an 8 byte pointer, MPI.jl will have to change too.
>
>     Jared Crean
>
>
> On 7/14/2015 1:04 PM, Matthew Knepley wrote:
>
>  On Tue, Jul 14, 2015 at 10:56 AM, Jared Crean <jcrean01 at gmail.com> wrote:
>
>>      Hello everyone,
>>         I got the package in a reasonably working state and Travis
>> testing setup, so I am putting the package up on Github.
>>
>>         https://github.com/JaredCrean2/PETSc.jl
>>
>>         There is still a lot more work to do, but its a start.
>>
>>         A couple questions:
>>         When looking though the code, I noticed the MPI communicator is
>> being passed as a 64 bit integer.  mpi.h typedefs it as an int, so
>> shouldn't it be a 32 bit integer?
>>
>
>  Some MPI implementations store the communicator as a pointer, which may
> be 64 bits. I think the only thing the standard says is
> that MPI_Comm should be defined.
>
>
>>          Also, is there a way to find out at runtime what datatype a
>> PetscScalar is?  It appears PetscDataTypeGetSize does not accept
>> PetscScalar as an argument.
>>
>
>  If PETSC_USE_COMPLEX is defined its PETSC_COMPLEX, otherwise its
> PETSC_REAL. You can also just use sizeof(PetscScalar). What do you
> want to do?
>
>    Thanks,
>
>       Matt
>
>
>>
>>     Jared Crean
>>
>>
>>
>> On 07/06/2015 09:02 AM, Matthew Knepley wrote:
>>
>>  On Mon, Jul 6, 2015 at 4:59 AM, Patrick Sanan <patrick.sanan at gmail.com>
>> wrote:
>>
>>> I had a couple of brief discussions about this at Juliacon as well. I
>>> think it would be useful, but there are a couple of things to think about
>>> from the start of any new attempt to do this:
>>> 1. As Jack pointed out, one issue is that the PETSc library must be
>>> compiled for a particular precision. This raises some questions - should
>>> several versions of the library be built to allow for flexibility?
>>> 2. An issue with wrapping PETSc is always that the flexibility of using
>>> the PETSc options paradigm is reduced - how can this be addressed?
>>> Could/should an expert user be able to access the options database
>>> directly, or would this be too much violence to the wrapper abstraction?
>>>
>>
>>  I have never understood why this is an issue. Can't you just wrap our
>> interface level, and use the options just as we do? That
>> is essentially what petsc4py does. What is limiting in this methodology?
>> On the other hand, requiring specific types, ala FEniCS,
>> is very limiting.
>>
>>     Matt
>>
>>
>>>  On Sat, Jul 4, 2015 at 11:00 PM, Jared Crean <jcrean01 at gmail.com>
>>> wrote:
>>>
>>>>  Hello,
>>>>      I am a graduate student working on a CFD code written in Julia,
>>>> and I am interested in using Petsc as a linear solver (and possibly for the
>>>> non-linear solves as well) for the code.  I discovered the Julia wrapper
>>>> file Petsc.jl in Petsc and have updated it to work with the current version
>>>> of Julia and the MPI.jl package, using only MPI for communication (I don't
>>>> think Julia's internal parallelism will scale well enough, at least not in
>>>> the near future).
>>>>
>>>>      I read the discussion on Github [
>>>> https://github.com/JuliaLang/julia/issues/2645], and it looks like
>>>> there currently is not a complete package to access Petsc from Julia.
>>>> With your permission, I would like to use the Petsc.jl file as the basis
>>>> for developing a package.  My plan is create a lower level interface that
>>>> exactly wraps Petsc functions, and then construct a higher level interface,
>>>> probably an object that is a subtype of Julia's AbstractArray, that allows
>>>> users to store values into Petsc vectors and matrices.  I am less
>>>> interested in integrating tightly with Julia's existing linear algebra
>>>> capabilities than ensuring good scalability.  The purpose of the high level
>>>> interface it simple to populate the vector or matrix.
>>>>
>>>>      What do you think, both about using the Petsc.jl file and the
>>>> overall approach?
>>>>
>>>>      Jared Crean
>>>>
>>>
>>>
>>
>>
>>  --
>> 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
>>
>>
>>
>
>
>  --
> 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
>
>
>


-- 
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
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