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

[Barry Smith]

   I just put it with the Fortran source code and compile it with the rest of the application code; here is the makefile I used 


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On Sep 26, 2013, at 10:14 AM, Christophe Ortiz <christophe.ortiz at ciemat.es> wrote:

> 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
> 
> 
> 
>