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

[Christophe Ortiz]

Hi Barry,

Thanks a lot for the codes ! I will test it and let you know if it works.

Christophe

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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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