Barry, If I frame your email, will you sign it for me? ;) I am traveling so I did not have much time to do it, even in my sleep, but Tim's solution is essentially right. Have a look at the attached code. I had to write my own interface to PetscOptionsGetEnum, but I have to do the equivalent of FIXCHAR by myself (basically appending //C_NULL_CHAR). I checked in the debugger, and the list argument that is passed to PetscOptionsGetEList is the same as the one passed from C. Is this what you want? Do you want to do the FIXCHAR business in the C or fortran side? I suspect that you would prefer not having to append the C_NULL_CHAR in fortran, but I can't figure how to do that without allocating a new array of strings, and causing a memory leak. What do you think? If this is not what you want, could you meet me half way and write the fortran interface you would like to use, in which case I will try to write the missing fortran parts. Blaise

Tim,

Thanks. But what I want is all bundled up a routine that takes in the Fortran array of character strings and allocates and copies over them to the C ptr business. Likely I could figure it out myself with but Blaise is such a Fortran wizard he can do it optimally in his sleep :-)

Barry

On May 25, 2012, at 8:14 PM, Tim Gallagher wrote:

...

For what it's worth, I answered a question about how to pass string arrays awhile ago on StackOverflow:

http://stackoverflow.com/questions/9686532/arrays-of-strings-in-fortran-c-br...

Tim

----- Original Message ----- From: "Barry Smith" <[email protected]> To: "For users of the development version of PETSc" <[email protected]> Sent: Friday, May 25, 2012 8:57:52 PM Subject: Re: [petsc-dev] What needs to be done before a release?

Blaise

If you provide a fortran function to convert an array of Fortran strings to an array of C strings and tell us how to delete the result then we'll provide a PetscOptionsGetEnum() for Fortran.

Barry

On May 2, 2012, at 12:02 PM, Blaise Bourdin wrote:

...

Barry,

...

...

Also, fortran wrappers over PetscOptionsEnum and PetscBagRegisterEnum would be nice. I understand that it is a bit tricky since it involves passing fortran arrays of strings.

Yup. We'd be willing to support these from FORTRAN but someone else has to do the dirty work of figuring out how to handle those array of strings (maybe F2003?).

I am attaching a simple proof of concept example that demonstrates how to write a fortran interface and call petsc C functions from fortran using F2003 C-interoperability instead of going through the fortran bindings.

Don't be put off by all the warnings if you use gfortran. They would be easy to avoid. Basically, right now, you detect the fortran integer and real kinds that match that of the C ones. It would be quite simple to get the fortran C-interoperable integer and real types associated with the C type of PetscInt, PetscReal etc.

Basically, we (I?) could write a fortran interface and a fortran function for the tricky functions involving arrays of string, instead of creating a custom binding in C. Are you willing to let some fortran pollution into the petsc code? Where would these function have to be?

Blaise

PS: you need FCFLAGS='-ffixed-line-length-none -ffree-line-length-none -ffree-form' or some subset of these to compile with gfortran. I'm not sure why these are not the default with a file suffix .F90

<PetscF2003Binding.F90> -- Department of Mathematics and Center for Computation & Technology Louisiana State University, Baton Rouge, LA 70803, USA Tel. +1 (225) 578 1612, Fax +1 (225) 578 4276 http://www.math.lsu.edu/~bourdin

-- Department of Mathematics and Center for Computation & Technology Louisiana State University, Baton Rouge, LA 70803, USA Tel. +1 (225) 578 1612, Fax +1 (225) 578 4276 http://www.math.lsu.edu/~bourdin