2: static char help[] = "Demonstrates calling a Fortran computational routine from C.\n\
  3: Also demonstrates passing  PETSc objects, MPI Communicators from C to Fortran\n\
  4: and from Fortran to C\n\n";

  6:  #include <petscvec.h>
  7: /*
  8:   Ugly stuff to insure the function names match between Fortran
  9:   and C. Sorry, but this is out of our PETSc hands to cleanup.
 10: */
 11: /*T
 12:    Concepts: vectors^fortran-c;
 13:    Processors: n
 14: T*/
 15:  #include <petsc/private/fortranimpl.h>
 16: #if defined(PETSC_HAVE_FORTRAN_CAPS)
 17: #define ex7f_ EX7F
 18: #define ex7c_ EX7C
 19: #elif !defined(PETSC_HAVE_FORTRAN_UNDERSCORE)
 20: #define ex7f_ ex7f
 21: #define ex7c_ ex7c
 22: #endif

 24: PETSC_INTERN void PETSC_STDCALL ex7f_(Vec*,int*);

 26: int main(int argc,char **args)
 27: {
 29:   PetscInt       m = 10;
 30:   int            fcomm;
 31:   Vec            vec;

 33:   PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
 34:   /* This function should be called to be able to use PETSc routines
 35:      from the FORTRAN subroutines needed by this program */

 37:   PetscInitializeFortran();

 39:   VecCreate(PETSC_COMM_WORLD,&vec);
 40:   VecSetSizes(vec,PETSC_DECIDE,m);
 41:   VecSetFromOptions(vec);

 43:   /*
 44:      Call Fortran routine - the use of MPI_Comm_c2f() allows
 45:      translation of the MPI_Comm from C so that it can be properly
 46:      interpreted from Fortran.
 47:   */
 48:   fcomm = MPI_Comm_c2f(PETSC_COMM_WORLD);

 50:   ex7f_(&vec,&fcomm);

 52:   VecView(vec,PETSC_VIEWER_STDOUT_WORLD);
 53:   VecDestroy(&vec);
 54:   PetscFinalize();
 55:   return ierr;
 56: }

 58: PETSC_INTERN void PETSC_STDCALL ex7c_(Vec *fvec,int *fcomm,PetscErrorCode *ierr)
 59: {
 60:   MPI_Comm comm;
 61:   PetscInt vsize;

 63:   /*
 64:     Translate Fortran integer pointer back to C and
 65:     Fortran Communicator back to C communicator
 66:   */
 67:   comm = MPI_Comm_f2c(*fcomm);

 69:   /* Some PETSc/MPI operations on Vec/Communicator objects */
 70:   *VecGetSize(*fvec,&vsize);
 71:   *MPI_Barrier(comm);

 73: }

 75: /*TEST

 77:    build:
 78:      depends: ex7f.F
 79:      requires: fortran

 81:    test:
 82:       nsize: 3
 83:       filter: sort -b |grep -v "MPI processes"
 84:       filter_output: sort -b

 86: TEST*/