!
!    Copyright 2017, L. Hüdepohl and A. Marek, MPCDF
!
!    This file is part of ELPA.
!
!    The ELPA library was originally created by the ELPA consortium,
!    consisting of the following organizations:
!
!    - Max Planck Computing and Data Facility (MPCDF), formerly known as
!      Rechenzentrum Garching der Max-Planck-Gesellschaft (RZG),
!    - Bergische Universität Wuppertal, Lehrstuhl für angewandte
!      Informatik,
!    - Technische Universität München, Lehrstuhl für Informatik mit
!      Schwerpunkt Wissenschaftliches Rechnen ,
!    - Fritz-Haber-Institut, Berlin, Abt. Theorie,
!    - Max-Plack-Institut für Mathematik in den Naturwissenschaften,
!      Leipzig, Abt. Komplexe Strukutren in Biologie und Kognition,
!      and
!    - IBM Deutschland GmbH
!
!    This particular source code file contains additions, changes and
!    enhancements authored by Intel Corporation which is not part of
!    the ELPA consortium.
!
!    More information can be found here:
!    http://elpa.mpcdf.mpg.de/
!
!    ELPA is free software: you can redistribute it and/or modify
!    it under the terms of the version 3 of the license of the
!    GNU Lesser General Public License as published by the Free
!    Software Foundation.
!
!    ELPA is distributed in the hope that it will be useful,
!    but WITHOUT ANY WARRANTY; without even the implied warranty of
!    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
!    GNU Lesser General Public License for more details.
!
!    You should have received a copy of the GNU Lesser General Public License
!    along with ELPA.  If not, see <http://www.gnu.org/licenses/>
!
!    ELPA reflects a substantial effort on the part of the original
!    ELPA consortium, and we ask you to respect the spirit of the
!    license that we chose: i.e., please contribute any changes you
!    may have back to the original ELPA library distribution, and keep
!    any derivatives of ELPA under the same license that we chose for
!    the original distribution, the GNU Lesser General Public License.
!
!> \brief Fortran module which provides the definition of the ELPA API. Do not use directly! Use the module "elpa"

#include "config-f90.h"

module elpa_api
  use elpa_constants
  use, intrinsic :: iso_c_binding
  implicit none

#include "src/elpa_generated_public_fortran_interfaces.h"

  integer, private, parameter :: earliest_api_version = EARLIEST_API_VERSION !< Definition of the earliest API version supported
                                                                             !< with the current release
  integer, private, parameter :: current_api_version  = CURRENT_API_VERSION  !< Definition of the current API version

  integer, private, parameter :: earliest_autotune_version = EARLIEST_AUTOTUNE_VERSION !< Definition of the earliest API version
                                                                                       !< which supports autotuning
  integer, private            :: api_version_set
  logical, private            :: initDone = .false.

  public :: elpa_t, &
      c_int, &
      c_double, c_double_complex, &
      c_float, c_float_complex

  !> \brief Abstract definition of the elpa_t type
  type, abstract :: elpa_t
    private


    !< these have to be public for proper bounds checking, sadly
    integer(kind=c_int), public, pointer :: na => NULL()
    integer(kind=c_int), public, pointer :: nev => NULL()
    integer(kind=c_int), public, pointer :: local_nrows => NULL()
    integer(kind=c_int), public, pointer :: local_ncols => NULL()
    integer(kind=c_int), public, pointer :: nblk => NULL()

    contains
      ! general
      procedure(elpa_setup_i),   deferred, public :: setup          !< method to setup an ELPA object
      procedure(elpa_destroy_i), deferred, public :: destroy        !< method to destroy an ELPA object

      ! key/value store
      generic, public :: set => &                                   !< export a method to set integer/double key/values
          elpa_set_integer, &
          elpa_set_double

      generic, public :: get => &                                   !< export a method to get integer/double key/values
          elpa_get_integer, &
          elpa_get_double

      procedure(elpa_is_set_i),  deferred, public :: is_set         !< method to check whether key/value is set
      procedure(elpa_can_set_i), deferred, public :: can_set        !< method to check whether key/value can be set

      ! Timer
      procedure(elpa_get_time_i), deferred, public :: get_time        !< method to get the times from the timer object
      procedure(elpa_print_times_i), deferred, public :: print_times  !< method to print the timings tree
      procedure(elpa_timer_start_i), deferred, public :: timer_start  !< method to start a time measurement
      procedure(elpa_timer_stop_i), deferred, public :: timer_stop    !< method to stop a time measurement


      ! Actual math routines
      generic, public :: eigenvectors => &                          !< method eigenvectors for solving the full eigenvalue problem
          elpa_eigenvectors_d, &                                    !< the eigenvalues and (parts of) the eigenvectors are computed
          elpa_eigenvectors_f, &                                    !< for symmetric real valued / hermitian complex valued matrices
          elpa_eigenvectors_dc, &
          elpa_eigenvectors_fc

      generic, public :: eigenvalues => &                           !< method eigenvalues for solving the eigenvalue problem
          elpa_eigenvalues_d, &                                     !< only the eigenvalues are computed
          elpa_eigenvalues_f, &                                     !< for symmetric real valued / hermitian complex valued matrices
          elpa_eigenvalues_dc, &
          elpa_eigenvalues_fc

      generic, public :: generalized_eigenvectors => &              !< method eigenvectors for solving the full generalized eigenvalue problem
          elpa_generalized_eigenvectors_d, &                        !< the eigenvalues and (parts of) the eigenvectors are computed
          elpa_generalized_eigenvectors_f, &                        !< for symmetric real valued / hermitian complex valued matrices
          elpa_generalized_eigenvectors_dc, &
          elpa_generalized_eigenvectors_fc

      generic, public :: generalized_eigenvalues => &              !< method eigenvectors for solving the full generalized eigenvalue problem
          elpa_generalized_eigenvalues_d, &                        !< only the eigenvalues
          elpa_generalized_eigenvalues_f, &                        !< for symmetric real valued / hermitian complex valued matrices
          elpa_generalized_eigenvalues_dc, &
          elpa_generalized_eigenvalues_fc

      generic, public :: hermitian_multiply => &                    !< method for a "hermitian" multiplication of matrices a and b
          elpa_hermitian_multiply_d, &                              !< for real valued matrices:   a**T * b
          elpa_hermitian_multiply_dc, &                             !< for complex valued matrices a**H * b
          elpa_hermitian_multiply_f, &
          elpa_hermitian_multiply_fc

      generic, public :: cholesky => &                              !< method for the cholesky factorisation of matrix a
          elpa_cholesky_d, &
          elpa_cholesky_f, &
          elpa_cholesky_dc, &
          elpa_cholesky_fc

      generic, public :: invert_triangular => &                     !< method to invert a upper triangular matrix a
          elpa_invert_trm_d, &
          elpa_invert_trm_f, &
          elpa_invert_trm_dc, &
          elpa_invert_trm_fc

      generic, public :: solve_tridiagonal => &                      !< method to solve the eigenvalue problem for a tridiagonal
          elpa_solve_tridiagonal_d, &                                !< matrix
          elpa_solve_tridiagonal_f

      procedure(print_settings_i), deferred, public :: print_settings !< method to print all parameters
      procedure(store_settings_i), deferred, public :: store_settings !< method to save all parameters
      procedure(load_settings_i), deferred, public :: load_settings !< method to save all parameters
#ifdef ENABLE_AUTOTUNING
      ! Auto-tune
      procedure(elpa_autotune_setup_i), deferred, public :: autotune_setup       !< method to prepare the ELPA autotuning
      procedure(elpa_autotune_step_i), deferred, public :: autotune_step         !< method to do an autotuning step
      procedure(elpa_autotune_set_best_i), deferred, public :: autotune_set_best !< method to set the best options
      procedure(elpa_autotune_print_best_i), deferred, public :: autotune_print_best !< method to print the best options
      procedure(elpa_autotune_print_state_i), deferred, public :: autotune_print_state !< method to print the state
      procedure(elpa_autotune_save_state_i), deferred, public :: autotune_save_state !< method to save the state
      procedure(elpa_autotune_load_state_i), deferred, public :: autotune_load_state !< method to load the state
#endif

      !> \brief These method have to be public, in order to be overrideable in the extension types
      procedure(elpa_set_integer_i), deferred, public :: elpa_set_integer
      procedure(elpa_set_double_i),  deferred, public :: elpa_set_double

      procedure(elpa_get_integer_i), deferred, public :: elpa_get_integer
      procedure(elpa_get_double_i),  deferred, public :: elpa_get_double

      procedure(elpa_eigenvectors_d_i),    deferred, public :: elpa_eigenvectors_d
      procedure(elpa_eigenvectors_f_i),    deferred, public :: elpa_eigenvectors_f
      procedure(elpa_eigenvectors_dc_i), deferred, public :: elpa_eigenvectors_dc
      procedure(elpa_eigenvectors_fc_i), deferred, public :: elpa_eigenvectors_fc

      procedure(elpa_eigenvalues_d_i),    deferred, public :: elpa_eigenvalues_d
      procedure(elpa_eigenvalues_f_i),    deferred, public :: elpa_eigenvalues_f
      procedure(elpa_eigenvalues_dc_i), deferred, public :: elpa_eigenvalues_dc
      procedure(elpa_eigenvalues_fc_i), deferred, public :: elpa_eigenvalues_fc

      procedure(elpa_generalized_eigenvectors_d_i),    deferred, public :: elpa_generalized_eigenvectors_d
      procedure(elpa_generalized_eigenvectors_f_i),    deferred, public :: elpa_generalized_eigenvectors_f
      procedure(elpa_generalized_eigenvectors_dc_i), deferred, public :: elpa_generalized_eigenvectors_dc
      procedure(elpa_generalized_eigenvectors_fc_i), deferred, public :: elpa_generalized_eigenvectors_fc

      procedure(elpa_generalized_eigenvalues_d_i),    deferred, public :: elpa_generalized_eigenvalues_d
      procedure(elpa_generalized_eigenvalues_f_i),    deferred, public :: elpa_generalized_eigenvalues_f
      procedure(elpa_generalized_eigenvalues_dc_i), deferred, public :: elpa_generalized_eigenvalues_dc
      procedure(elpa_generalized_eigenvalues_fc_i), deferred, public :: elpa_generalized_eigenvalues_fc

      procedure(elpa_hermitian_multiply_d_i),  deferred, public :: elpa_hermitian_multiply_d
      procedure(elpa_hermitian_multiply_f_i),  deferred, public :: elpa_hermitian_multiply_f
      procedure(elpa_hermitian_multiply_dc_i), deferred, public :: elpa_hermitian_multiply_dc
      procedure(elpa_hermitian_multiply_fc_i), deferred, public :: elpa_hermitian_multiply_fc

      procedure(elpa_cholesky_d_i),    deferred, public :: elpa_cholesky_d
      procedure(elpa_cholesky_f_i),    deferred, public :: elpa_cholesky_f
      procedure(elpa_cholesky_dc_i), deferred, public :: elpa_cholesky_dc
      procedure(elpa_cholesky_fc_i), deferred, public :: elpa_cholesky_fc

      procedure(elpa_invert_trm_d_i),    deferred, public :: elpa_invert_trm_d
      procedure(elpa_invert_trm_f_i),    deferred, public :: elpa_invert_trm_f
      procedure(elpa_invert_trm_dc_i), deferred, public :: elpa_invert_trm_dc
      procedure(elpa_invert_trm_fc_i), deferred, public :: elpa_invert_trm_fc

      procedure(elpa_solve_tridiagonal_d_i), deferred, public :: elpa_solve_tridiagonal_d
      procedure(elpa_solve_tridiagonal_f_i), deferred, public :: elpa_solve_tridiagonal_f
  end type elpa_t

#ifdef ENABLE_AUTOTUNING
  !> \brief Abstract definition of the elpa_autotune type
  type, abstract :: elpa_autotune_t
    private
    contains
      procedure(elpa_autotune_destroy_i), deferred, public :: destroy
      procedure(elpa_autotune_print_i), deferred, public :: print
  end type
#endif

  !> \brief definition of helper function to get C strlen
  !> Parameters
  !> \details
  !> \param   ptr         type(c_ptr) : pointer to string
  !> \result  size        integer(kind=c_size_t) : length of string
  interface
    pure function elpa_strlen_c(ptr) result(size) bind(c, name="strlen")
      use, intrinsic :: iso_c_binding
      implicit none
      type(c_ptr), intent(in), value :: ptr
      integer(kind=c_size_t) :: size
    end function
  end interface


  !> \brief abstract definition of the ELPA setup method
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object
  !> \result  error       integer : error code, which can be queried with elpa_strerr()
  abstract interface
    function elpa_setup_i(self) result(error)
      import elpa_t
      implicit none
      class(elpa_t), intent(inout)   :: self
      integer                        :: error
    end function
  end interface

  !> \brief abstract definition of the print_settings method
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object
  !> \param   error       integer, optional
  !> Prints all the elpa parameters
  abstract interface
    subroutine print_settings_i(self, error)
      import elpa_t
      implicit none
      class(elpa_t), intent(inout)   :: self
#ifdef USE_FORTRAN2008
      integer, optional, intent(out) :: error
#else
      integer, intent(out)           :: error
#endif
    end subroutine
  end interface

  !> \brief abstract definition of the store_settings method
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object
  !> \param   file_name   string, the name of the file where to save the parameters
  !> \param   error       integer, optional
  !> Saves all the elpa parameters
  abstract interface
    subroutine store_settings_i(self, file_name, error)
      import elpa_t
      implicit none
      class(elpa_t), intent(inout)  :: self
      character(*), intent(in)      :: file_name
#ifdef USE_FORTRAN2008
      integer, optional, intent(out):: error
#else
      integer, intent(out)          :: error
#endif
    end subroutine
  end interface

  !> \brief abstract definition of the load_settings method
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object
  !> \param   file_name   string, the name of the file from which to load the parameters
  !> \param   error       integer, optional
  !> Loads all the elpa parameters
  abstract interface
    subroutine load_settings_i(self, file_name, error)
      import elpa_t
      implicit none
      class(elpa_t), intent(inout)   :: self
      character(*), intent(in)       :: file_name
#ifdef USE_FORTRAN2008
      integer, optional, intent(out) :: error
#else
      integer, intent(out)           :: error
#endif
    end subroutine
  end interface

#ifdef ENABLE_AUTOTUNING
  !> \brief abstract definition of the autotune setup method
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object, which should be tuned
  !> \param   level       integer: the level of "thoroughness" of the tuning steps
  !> \param   domain      integer: domain (real/complex) which should be tuned
  !> \result  tune_state  class(elpa_autotune_t): the autotuning object
  abstract interface
    function elpa_autotune_setup_i(self, level, domain, error) result(tune_state)
      import elpa_t, elpa_autotune_t
      implicit none
      class(elpa_t), intent(inout), target :: self
      integer, intent(in)                  :: level, domain
      class(elpa_autotune_t), pointer      :: tune_state
#ifdef USE_FORTRAN2008
      integer , optional                   :: error
#else
      integer                              :: error
#endif
    end function
  end interface


  !> \brief abstract definition of the autotune step method
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object, which should be tuned
  !> \param   tune_state  class(elpa_autotune_t): the autotuning object
  !> \param   unfinished  logical: state whether tuning is unfinished or not
  !> \param   error       integer, optional
  abstract interface
    function elpa_autotune_step_i(self, tune_state, error) result(unfinished)
      import elpa_t, elpa_autotune_t
      implicit none
      class(elpa_t), intent(inout)                  :: self
      class(elpa_autotune_t), intent(inout), target :: tune_state
      logical                                       :: unfinished
#ifdef USE_FORTRAN2008
      integer, optional, intent(out)                :: error
#else
      integer, intent(out)                          :: error
#endif
    end function
  end interface

  
  !> \brief abstract definition of the autotune set_best method
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object, which should be tuned
  !> \param   tune_state  class(elpa_autotune_t): the autotuning object
  !> \param   error       integer, optional
  !> Sets the best combination of ELPA options
  abstract interface
    subroutine elpa_autotune_set_best_i(self, tune_state, error)
      import elpa_t, elpa_autotune_t
      implicit none
      class(elpa_t), intent(inout)               :: self
      class(elpa_autotune_t), intent(in), target :: tune_state
#ifdef USE_FORTRAN2008
      integer, optional, intent(out)             :: error
#else
      integer, intent(out)                       :: error

#endif
    end subroutine
  end interface

  
  !> \brief abstract definition of the autotune print best method
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object, which should be tuned
  !> \param   tune_state  class(elpa_autotune_t): the autotuning object
  !> \param   error       integer, optional
  !> Prints the best combination of ELPA options
  abstract interface
    subroutine elpa_autotune_print_best_i(self, tune_state, error)
      import elpa_t, elpa_autotune_t
      implicit none
      class(elpa_t), intent(inout)               :: self
      class(elpa_autotune_t), intent(in), target :: tune_state
#ifdef USE_FORTRAN2008
      integer, optional, intent(out)             :: error
#else
      integer, intent(out)                       :: error

#endif
    end subroutine
  end interface

  !> \brief abstract definition of the autotune print state method
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object, which should be tuned
  !> \param   tune_state  class(elpa_autotune_t): the autotuning object
  !> \param   error       integer, optional
  !> Prints the autotuning state
  abstract interface
    subroutine elpa_autotune_print_state_i(self, tune_state, error)
      import elpa_t, elpa_autotune_t
      implicit none
      class(elpa_t), intent(inout)               :: self
      class(elpa_autotune_t), intent(in), target :: tune_state
#ifdef USE_FORTRAN2008
      integer, optional, intent(out)             :: error
#else
      integer,  intent(out)                      :: error
#endif
    end subroutine
  end interface

  !> \brief abstract definition of the autotune save state method
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object, which should be tuned
  !> \param   tune_state  class(elpa_autotune_t): the autotuning object
  !> \param   file_name   string, the name of the file where to save the state
  !> \param   error       integer, optional
  !> Saves the autotuning state
  abstract interface
    subroutine elpa_autotune_save_state_i(self, tune_state, file_name, error)
      import elpa_t, elpa_autotune_t
      implicit none
      class(elpa_t), intent(inout)               :: self
      class(elpa_autotune_t), intent(in), target :: tune_state
      character(*), intent(in)                   :: file_name
#ifdef USE_FORTRAN2008
      integer, optional, intent(out)             :: error
#else
      integer, intent(out)                       :: error
#endif
    end subroutine
  end interface

  !> \brief abstract definition of the autotune load state method
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object, which is being tuned
  !> \param   tune_state  class(elpa_autotune_t): the autotuning object
  !> \param   file_name   string, the name of the file from which to load the autotuning state
  !> \param   error       integer, optional
  !> Loads all the elpa parameters
  abstract interface
    subroutine elpa_autotune_load_state_i(self, tune_state, file_name, error)
      import elpa_t, elpa_autotune_t
      implicit none
      class(elpa_t), intent(inout)               :: self
      class(elpa_autotune_t), intent(in), target :: tune_state
      character(*), intent(in)                   :: file_name
#ifdef USE_FORTRAN2008
      integer, optional, intent(out)             :: error
#else
      integer, intent(out)                       :: error
#endif
    end subroutine
  end interface
#endif

  !> \brief abstract definition of set method for integer values
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object
  !> \param   name        string: the name of the key
  !> \param   value       integer : the value to set for the key
  !> \param   error       integer, optional : error code, which can be queried with elpa_strerr()
  abstract interface
    subroutine elpa_set_integer_i(self, name, value, error)
      use iso_c_binding
      import elpa_t
      implicit none
      class(elpa_t)                   :: self
      character(*), intent(in)        :: name
      integer(kind=c_int), intent(in) :: value
#ifdef USE_FORTRAN2008
      integer, optional               :: error
#else
      integer                         :: error
#endif
    end subroutine
  end interface


  !> \brief abstract definition of get method for integer values
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object
  !> \param   name        string: the name of the key
  !> \param   value       integer : the value corresponding to the key
  !> \param   error       integer, optional : error code, which can be queried with elpa_strerr()
  abstract interface
    subroutine elpa_get_integer_i(self, name, value, error)
      use iso_c_binding
      import elpa_t
      implicit none
      class(elpa_t)                  :: self
      character(*), intent(in)       :: name
      integer(kind=c_int)            :: value
#ifdef USE_FORTRAN2008
      integer, intent(out), optional :: error
#else
      integer, intent(out)           :: error
#endif
    end subroutine
  end interface


  !> \brief abstract definition of is_set method for integer values
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object
  !> \param   name        string: the name of the key
  !> \result  state       integer : 1 is set, 0 if not, else a negativ error code
  !>                                                    which can be queried with elpa_strerr
  abstract interface
    function elpa_is_set_i(self, name) result(state)
      import elpa_t
      implicit none
      class(elpa_t)            :: self
      character(*), intent(in) :: name
      integer                  :: state
    end function
  end interface


  !> \brief abstract definition of can_set method for integer values
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object
  !> \param   name        string: the name of the key
  !> \param   value       integer: the valye to associate with the key
  !> \result  state       integer : 1 is set, 0 if not, else a negativ error code
  !>                                                    which can be queried with elpa_strerr
  abstract interface
    function elpa_can_set_i(self, name, value) result(state)
      import elpa_t, c_int
      implicit none
      class(elpa_t)                   :: self
      character(*), intent(in)        :: name
      integer(kind=c_int), intent(in) :: value
      integer                         :: state
    end function
  end interface


  !> \brief abstract definition of set method for double values
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object
  !> \param   name        string: the name of the key
  !? \param   value       double: the value to associate with the key
  !> \param   error       integer. optional : error code, which can be queried with elpa_strerr
  abstract interface
    subroutine elpa_set_double_i(self, name, value, error)
      use iso_c_binding
      import elpa_t
      implicit none
      class(elpa_t)                   :: self
      character(*), intent(in)        :: name
      real(kind=c_double), intent(in) :: value
#ifdef USE_FORTRAN2008
      integer, optional               :: error
#else
      integer                         :: error
#endif
    end subroutine
  end interface


  !> \brief abstract definition of get method for double values
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object
  !> \param   name        string: the name of the key
  !> \param   value       double: the value associated with the key
  !> \param   error       integer, optional : error code, which can be queried with elpa_strerr
  abstract interface
    subroutine elpa_get_double_i(self, name, value, error)
      use iso_c_binding
      import elpa_t
      implicit none
      class(elpa_t)                  :: self
      character(*), intent(in)       :: name
      real(kind=c_double)            :: value
#ifdef USE_FORTRAN2008
      integer, intent(out), optional :: error
#else
      integer, intent(out)           :: error
#endif
    end subroutine
  end interface


  !> \brief abstract definition of associate method for integer pointers
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object
  !> \param   name        string: the name of the key
  !> \result  value       integer, pointer: the value associated with the key
  abstract interface
    function elpa_associate_int_i(self, name) result(value)
      use iso_c_binding
      import elpa_t
      implicit none
      class(elpa_t)                  :: self
      character(*), intent(in)       :: name
      integer(kind=c_int), pointer   :: value
    end function
  end interface


  ! Timer routines

  !> \brief abstract definition of get_time method to querry the timer
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object
  !> \param   name1..6    string: the name of the timer entry, supports up to 6 levels
  !> \result  s           double: the time for the entry name1..6
  abstract interface
    function elpa_get_time_i(self, name1, name2, name3, name4, name5, name6) result(s)
      import elpa_t, c_double
      implicit none
      class(elpa_t), intent(in) :: self
      ! this is clunky, but what can you do..
      character(len=*), intent(in), optional :: name1, name2, name3, name4, name5, name6
      real(kind=c_double) :: s
    end function
  end interface


  !> \brief abstract definition of print method for timer
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object
  abstract interface
    subroutine elpa_print_times_i(self, name1, name2, name3, name4)
      import elpa_t
      implicit none
      class(elpa_t), intent(in) :: self
      character(len=*), intent(in), optional :: name1, name2, name3, name4
    end subroutine
  end interface


  !> \brief abstract definition of the start method for timer
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object
  !> \param   name        character(len=*) the name of the entry int the timer tree
  abstract interface
    subroutine elpa_timer_start_i(self, name)
      import elpa_t
      implicit none
      class(elpa_t), intent(inout) :: self
      character(len=*), intent(in) :: name
    end subroutine
  end interface


  !> \brief abstract definition of the stop method for timer
  !> Parameters
  !> \details
  !> \param   self        class(elpa_t): the ELPA object
  !> \param   name        character(len=*) the name of the entry int the timer tree
  abstract interface
    subroutine elpa_timer_stop_i(self, name)
      import elpa_t
      implicit none
      class(elpa_t), intent(inout) :: self
      character(len=*), intent(in) :: name
    end subroutine
  end interface

  ! Actual math routines

#define REALCASE 1
#define DOUBLE_PRECISION 1
#include "general/precision_macros.h"
#include "elpa_api_math_template.F90"
#undef REALCASE
#undef DOUBLE_PRECISION

#define REALCASE 1
#define SINGLE_PRECISION 1
#include "general/precision_macros.h"
#include "elpa_api_math_template.F90"
#undef REALCASE
#undef SINGLE_PRECISION

#define COMPLEXCASE 1
#define DOUBLE_PRECISION 1
#include "general/precision_macros.h"
#include "elpa_api_math_template.F90"
#undef DOUBLE_PRECISION
#undef COMPLEXCASE

#define COMPLEXCASE 1
#define SINGLE_PRECISION
#include "general/precision_macros.h"
#include "elpa_api_math_template.F90"
#undef COMPLEXCASE
#undef SINGLE_PRECISION

! end of math routines

  !> \brief abstract definition of interface to destroy an ELPA object
  !> Parameters
  !> \param   self        class(elpa_t), the ELPA object
  !> \param   error       integer, optional, the error code
  abstract interface
    subroutine elpa_destroy_i(self, error)
      import elpa_t
      implicit none
      class(elpa_t)                  :: self
#ifdef USE_FORTRAN2008
      integer, optional, intent(out) :: error
#else
      integer, intent(out)           :: error
#endif
    end subroutine
  end interface

#ifdef ENABLE_AUTOTUNING
  !> \brief abstract definition of interface to print the autotuning state
  !> Parameters
  !> \param   self        class(elpa_autotune_t): the ELPA autotune object
  abstract interface
    subroutine elpa_autotune_print_i(self, error)
      import elpa_autotune_t
      implicit none
      class(elpa_autotune_t), intent(in) :: self
#ifdef USE_FORTRAN2008
      integer, intent(out), optional     :: error
#else
      integer, intent(out)               :: error
#endif

    end subroutine
  end interface

 
  !> \brief abstract definition of interface to destroy the autotuning state
  !> Parameters
  !> \param   self        class(elpa_autotune_t): the ELPA autotune object
  abstract interface
    subroutine elpa_autotune_destroy_i(self, error)
      import elpa_autotune_t
      implicit none
      class(elpa_autotune_t), intent(inout) :: self
#ifdef USE_FORTRAN2008
      integer, optional, intent(out)        :: error
#else
      integer, intent(out)                  :: error
#endif
    end subroutine
  end interface
#endif

  contains


    !> \brief function to intialize the ELPA library
    !> Parameters
    !> \param   api_version integer: api_version that ELPA should use
    !> \result  error       integer: error code, which can be queried with elpa_strerr
    !
    !c> int elpa_init(int api_version);
    function elpa_init(api_version) result(error) bind(C, name="elpa_init")
      use elpa_utilities, only : error_unit
      use iso_c_binding
      integer(kind=c_int), intent(in), value :: api_version
      integer(kind=c_int)                    :: error

      if (earliest_api_version <= api_version .and. api_version <= current_api_version) then
        initDone = .true.
        api_version_set = api_version
        error = ELPA_OK
      else
        write(error_unit, "(a,i0,a)") "ELPA: Error API version ", api_version," is not supported by this library"
        error = ELPA_ERROR_API_VERSION
      endif
    end function


    !> \brief function to check whether the ELPA library has been correctly initialised
    !> Parameters
    !> \result  state      integer: state is either ELPA_OK or ELPA_ERROR, which can be queried with elpa_strerr
    function elpa_initialized() result(state)
      integer :: state
      if (initDone) then
        state = ELPA_OK
      else
        state = ELPA_ERROR_CRITICAL
      endif
    end function

    function elpa_get_api_version() result(api_version)
       integer :: api_version

       api_version = api_version_set
    end function

#ifdef OPTIONAL_C_ERROR_ARGUMENT
    !c_o> #ifdef OPTIONAL_C_ERROR_ARGUMENT
    !c_o> #define elpa_uninit(...) CONC(elpa_uninit, NARGS(__VA_ARGS__))(__VA_ARGS__)
    !c_o> #endif
#endif
    !> \brief subroutine to uninit the ELPA library. Does nothing at the moment. Might do sth. later
    !
#ifdef OPTIONAL_C_ERROR_ARGUMENT
    !c_o> #ifdef OPTIONAL_C_ERROR_ARGUMENT
    !c_o> void elpa_uninit1(int *error);
    !c_o> void elpa_uninit0();
    !c_o> #endif
    subroutine elpa_uninit_c1(error) bind(C, name="elpa_uninit1")
      integer(kind=c_int)        :: error
      call elpa_uninit(error)
    end subroutine

    subroutine elpa_uninit_c0() bind(C, name="elpa_uninit0")
      call elpa_uninit()
    end subroutine
#else
    !c_no> #ifndef OPTIONAL_C_ERROR_ARGUMENT
    !c_no> void elpa_uninit(int *error);
    !c_no> #endif
    subroutine elpa_uninit_c(error) bind(C, name="elpa_uninit")
      integer(kind=c_int)        :: error
      call elpa_uninit(error)
    end subroutine
#endif

    subroutine elpa_uninit(error)
#ifdef USE_FORTRAN2008
      integer, optional, intent(out) :: error
#else
      integer, intent(out)           :: error
#endif
#ifdef USE_FORTRAN2008
      if (present(error)) then
        error = ELPA_OK
        return
      endif
#endif
    end subroutine
    !> \brief helper function for error strings
    !> Parameters
    !> \param   elpa_error  integer: error code to querry
    !> \result  string      string:  error string
    function elpa_strerr(elpa_error) result(string)
      integer, intent(in) :: elpa_error
      character(kind=C_CHAR, len=elpa_strlen_c(elpa_strerr_c(elpa_error))), pointer :: string
      call c_f_pointer(elpa_strerr_c(elpa_error), string)
    end function


    !> \brief helper function for c strings
    !> Parameters
    !> \param   ptr         type(c_ptr)
    !> \result  string      string
    function elpa_c_string(ptr) result(string)
      use, intrinsic :: iso_c_binding
      type(c_ptr), intent(in) :: ptr
      character(kind=c_char, len=elpa_strlen_c(ptr)), pointer :: string
      call c_f_pointer(ptr, string)
    end function


    !> \brief function to convert an integer in its string representation
    !> Parameters
    !> \param   name        string: the key
    !> \param   value       integer: the value correponding to the key
    !> \param   error       integer, optional: error code, which can be queried with elpa_strerr()
    !> \result  string      string: the string representation
    function elpa_int_value_to_string(name, value, error) result(string)
      use elpa_utilities, only : error_unit
      implicit none
      character(kind=c_char, len=*), intent(in) :: name
      integer(kind=c_int), intent(in) :: value
      integer(kind=c_int), intent(out), optional :: error

#ifdef PGI_VARIABLE_STRING_BUG
      character(kind=c_char, len=elpa_int_value_to_strlen_c(name // C_NULL_CHAR, value)), pointer :: string_ptr
      character(kind=c_char, len=elpa_int_value_to_strlen_c(name // C_NULL_CHAR, value)) :: string
#else
      character(kind=c_char, len=elpa_int_value_to_strlen_c(name // C_NULL_CHAR, value)), pointer :: string
#endif

      integer(kind=c_int) :: actual_error
      type(c_ptr) :: ptr

      actual_error = elpa_int_value_to_string_c(name // C_NULL_CHAR, value, ptr)
      if (c_associated(ptr)) then
#ifdef PGI_VARIABLE_STRING_BUG
        call c_f_pointer(ptr, string_ptr)
        string = string_ptr
#else
        call c_f_pointer(ptr, string)
#endif
      else
#ifdef PGI_VARIABLE_STRING_BUG
        nullify(string_ptr)
#else
        nullify(string)
#endif
      endif

      if (present(error)) then
        error = actual_error
      else if (actual_error /= ELPA_OK) then
        write(error_unit,'(a,i0,a)') "ELPA: Error converting value '", value, "' to a string for option '" // &
                name // "' and you did not check for errors: " // elpa_strerr(actual_error)
      endif
    end function


    !> \brief function to convert a string in its integer representation:
    !> Parameters
    !> \param   name        string: the key
    !> \param   string      string: the string whose integer representation should be associated with the key
    !> \param   error       integer, optional: error code, which can be queried with elpa_strerr()
    !> \result  value       integer: the integer representation of the string
    function elpa_int_string_to_value(name, string, error) result(value)
      use elpa_generated_fortran_interfaces
      use elpa_utilities, only : error_unit
      implicit none
      character(kind=c_char, len=*), intent(in)         :: name
      character(kind=c_char, len=*), intent(in), target :: string
      integer(kind=c_int), intent(out), optional        :: error
      integer(kind=c_int)                               :: actual_error

      integer(kind=c_int)                               :: value

      actual_error = elpa_int_string_to_value_c(name // C_NULL_CHAR, string // C_NULL_CHAR, value)

      if (present(error)) then
        error = actual_error
      else if (actual_error /= ELPA_OK) then
        write(error_unit,'(a)') "ELPA: Error converting string '" // string // "' to value for option '" // &
                name // "' and you did not check for errors: " // elpa_strerr(actual_error)
      endif
    end function


    !> \brief function to get the number of possible choices for an option
    !> Parameters
    !> \param   option_name string:   the option
    !> \result  number      integer:  the total number of possible values to be chosen
    function elpa_option_cardinality(option_name) result(number)
      use elpa_generated_fortran_interfaces
      character(kind=c_char, len=*), intent(in) :: option_name
      integer                                   :: number
      number = elpa_option_cardinality_c(option_name // C_NULL_CHAR)
    end function


    !> \brief function to enumerate an option
    !> Parameters
    !> \param   option_name string: the option
    !> \param   i           integer
    !> \result  option      integer
    function elpa_option_enumerate(option_name, i) result(option)
      use elpa_generated_fortran_interfaces
      character(kind=c_char, len=*), intent(in) :: option_name
      integer, intent(in)                       :: i
      integer                                   :: option
      option = elpa_option_enumerate_c(option_name // C_NULL_CHAR, i)
    end function

end module