[petsc-users] Back to struct in Fortran to represent field with dof > 1

[Christophe Ortiz]

By the way, what should I do with the small .c code ? Where should I put it
?

Christophe


>
> On Thu, Sep 26, 2013 at 4:09 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>>
>>    Christophe,
>>
>>      Despite my LinkIn Endorsement for expertise in Fortran :-) I cannot
>> pretend to be an expert in FortranXX but I have cooked up an example
>> demonstrating accessing the Vec entries as if they are in an array of
>> derived types. I've attached the example code; there needs to be a small C
>> stub that defines the functions for your specific derived type name.
>> Note that it will only work I think if your N is a compile time constant.
>>
>>
>>
>>
>>     It worked with
>> ~/Downloads$ gfortran --version
>> GNU Fortran (GCC) 4.8.1 20130404 (prerelease)
>>
>>
>>     I do not understand exactly why it works since it uses
>> F90Array1dCreate(fa,PETSC_SCALAR,1,len,ptr PETSC_F90_2PTR_PARAM(ptrd));
>> which has a single PETSC_SCALAR as a building block but … I hope it works
>> for you. If it doesn't, let us know the compiler you are using and we may
>> be able to get it working for that compiler.
>>
>>    Barry
>>
>>
>>
>>
>> On Sep 26, 2013, at 4:41 AM, Christophe Ortiz <christophe.ortiz at ciemat.es>
>> wrote:
>>
>> > Hi all,
>> >
>> > Me again !
>> >
>> > I have read in previous posts that it is hard in Fortran to declare
>> something similar to a typedef struct in C to manage a multicomponent
>> problem.
>> >
>> > Is it still the case ? Has the problem been solved ?
>> >
>> > I am asking because my plan is to implement a multicomponent problem
>> (in 1D), with many components that will be organized in arrays of two
>> dimensions. In C I could define
>> >
>> > typedef struct{
>> > PetscScalar U;
>> > PetscScalar V;
>> > PetscScalar A[N][N];
>> > } Field;
>> >
>> > and then I could calculate the residual function with
>> >
>> > F[i].U = ...
>> > F[i].V = ...
>> > F[i].A[k][n] = ...
>> >
>> > which is quite convenient.
>> >
>> > If in Fortran it is not possible to use a struct as in C, I am afraid
>> I'll have to deal with
>> >
>> > F(jdof,i) = ...
>> >
>> > where I will have only jdof to address U, V and A[ ][ ], which can be
>> difficult and not very convenient I guess. Before I move all my code to C,
>> does anyone have an alternative idea to manage this multi(many)component
>> problem in Fortran ?
>> >
>> > Many thanks in advance for your help and suggestion !
>> >
>> > Christophe
>>
>>
>>
>
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