FORTRAN interface

The FORTRAN interface is based on the ISO_C_BINDING feature, which is available for FORTRAN 2003 or later. The usage of FORTRAN interface is very similar to the C interface as given in the Tutorial section.

In FORTRAN, the PPEXSIPlan data type is c_intptr_t (or equivalently INTEGER*8). The naming of the subroutines is similar to the C interface as in c_pexsi_interface.h. All FORTRAN interface routines are in f_interface.f90. For instance, the subroutine PPEXSIPlanInitialize (C/C++) corresponds to the subroutine f_ppexsi_plan_initialize (FORTRAN).

Example: Parallel selected inversion for a real symmetric matrix

integer(c_intptr_t)    :: plan
type(f_ppexsi_options) :: options

! Initialize PEXSI. 
! PPEXSIPlan is a handle communicating with the C++ internal data structure 

plan = f_ppexsi_plan_initialize(&
  mpi_comm_world,&
  nprow,&
  npcol,&
  mpirank,&
  info )

! Tuning parameters of PEXSI. The default options is reasonable to
! start, and the parameters in options can be changed. 
call f_ppexsi_set_default_options(&
  options )

! Load the matrix into the internal data structure 
call f_ppexsi_load_real_symmetric_hs_matrix(&
      plan,&       
      options,&
      nrows,&
      nnz,&
      nnzlocal,&
      numcollocal,&
      colptrlocal,& 
      rowindlocal,&
      hnzvallocal,&
      1,&
      snzvallocal,&
      info ) 

! Factorize the matrix symbolically
call f_ppexsi_symbolic_factorize_real_symmetric_matrix(&
  plan,&
  options,&
  info)

! Main routine for computing selected elements and save into AinvnzvalLocal
call f_ppexsi_selinv_real_symmetric_matrix(& plan,&
  options,&
  anzvallocal,&
  ainvnzvallocal,&
  info)

! Post processing step...

! Release the data saved in the plan
call f_ppexsi_plan_finalize( plan, info )

The examples of the FORTRAN interface can be found under fortran/ directory, including f_driver_pselinv_real.f90, f_driver_pselinv_complex.f90, f_driver_ksdft.f90.