!--------------------------------------------------------------------------------------------------!
!   CP2K: A general program to perform molecular dynamics simulations                              !
!   Copyright 2000-2025 CP2K developers group <https://cp2k.org>                                   !
!                                                                                                  !
!   SPDX-License-Identifier: GPL-2.0-or-later                                                      !
!--------------------------------------------------------------------------------------------------!

! **************************************************************************************************
!> \brief The methods which allow to analyze and manipulate the arnoldi procedure
!>        The main routine and this should eb the only public access point for the
!>        method
!> \par History
!>       2014.09 created [Florian Schiffmann]
!> \author Florian Schiffmann
! **************************************************************************************************

MODULE arnoldi_data_methods
   USE arnoldi_types, ONLY: &
      arnoldi_control_type, arnoldi_data_c_type, arnoldi_data_d_type, arnoldi_data_s_type, &
      arnoldi_data_type, arnoldi_data_z_type, get_control, get_data_c, get_data_d, get_data_s, &
      get_data_z, get_evals_c, get_evals_d, get_evals_s, get_evals_z, get_sel_ind, has_d_cmplx, &
      has_d_real, set_control, set_data_c, set_data_d, set_data_s, &
      set_data_z
   USE cp_dbcsr_api, ONLY: &
      dbcsr_distribution_get, dbcsr_distribution_type, dbcsr_get_data_p, dbcsr_get_data_type, &
      dbcsr_get_info, dbcsr_get_matrix_type, dbcsr_mp_grid_setup, dbcsr_p_type, dbcsr_release, &
      dbcsr_type, dbcsr_type_complex_8, dbcsr_type_real_8, dbcsr_type_symmetric
   USE dbcsr_vector, ONLY: create_col_vec_from_matrix
   USE kinds, ONLY: real_8
   USE util, ONLY: sort
#include "../base/base_uses.f90"

   IMPLICIT NONE

   PRIVATE

   PUBLIC :: select_evals, get_selected_ritz_val, arnoldi_is_converged, &
             arnoldi_data_type, get_nrestart, set_arnoldi_initial_vector, &
             setup_arnoldi_data, deallocate_arnoldi_data, get_selected_ritz_vector

CONTAINS

! **************************************************************************************************
!> \brief This routine sets the environment for the arnoldi iteration and
!>        the krylov subspace creation. All simulation parameters have to be given
!>        at this stage so the rest can run fully automated
!>        In addition, this routine allocates the data necessary for
!> \param arnoldi_data this type which gets filled with information and
!>        on output contains all information necessary to extract
!>        whatever the user desires
!> \param matrix vector of matrices, only the first gets used to get some dimensions
!>        and parallel information needed later on
!> \param max_iter maximum dimension of the krylov subspace
!> \param threshold convergence threshold, this is used for both subspace and eigenval
!> \param selection_crit integer defining according to which criterion the
!>        eigenvalues are selected for the subspace
!> \param nval_request for some sel_crit useful, how many eV to select
!> \param nrestarts ...
!> \param generalized_ev ...
!> \param iram ...
! **************************************************************************************************
   SUBROUTINE setup_arnoldi_data(arnoldi_data, matrix, max_iter, threshold, selection_crit, &
                                 nval_request, nrestarts, generalized_ev, iram)
      TYPE(arnoldi_data_type)                            :: arnoldi_data
      TYPE(dbcsr_p_type), DIMENSION(:)                   :: matrix
      INTEGER                                            :: max_iter
      REAL(real_8)                                       :: threshold
      INTEGER                                            :: selection_crit, nval_request, nrestarts
      LOGICAL                                            :: generalized_ev, iram

      CALL setup_arnoldi_control(arnoldi_data, matrix, max_iter, threshold, selection_crit, &
                                 nval_request, nrestarts, generalized_ev, iram)

      SELECT CASE (dbcsr_get_data_type(matrix(1)%matrix))
      CASE (dbcsr_type_real_8)
         CALL setup_arnoldi_data_d(arnoldi_data, matrix, max_iter)
      CASE (dbcsr_type_complex_8)
         CALL setup_arnoldi_data_z(arnoldi_data, matrix, max_iter)
      END SELECT

   END SUBROUTINE setup_arnoldi_data

! **************************************************************************************************
!> \brief Creates the control type for arnoldi, see above for details
!> \param arnoldi_data ...
!> \param matrix ...
!> \param max_iter ...
!> \param threshold ...
!> \param selection_crit ...
!> \param nval_request ...
!> \param nrestarts ...
!> \param generalized_ev ...
!> \param iram ...
! **************************************************************************************************
   SUBROUTINE setup_arnoldi_control(arnoldi_data, matrix, max_iter, threshold, selection_crit, nval_request, &
                                    nrestarts, generalized_ev, iram)
      TYPE(arnoldi_data_type)                            :: arnoldi_data
      TYPE(dbcsr_p_type), DIMENSION(:)                   :: matrix
      INTEGER                                            :: max_iter
      REAL(real_8)                                       :: threshold
      INTEGER                                            :: selection_crit, nval_request, nrestarts
      LOGICAL                                            :: generalized_ev, iram

      INTEGER :: pcol_handle, group_handle
      LOGICAL                                            :: subgroups_defined
      TYPE(arnoldi_control_type), POINTER                :: control
      TYPE(dbcsr_distribution_type)                      :: distri

      ALLOCATE (control)
! Fill the information which will later on control the behavior of the arnoldi method and allow synchronization
      CALL dbcsr_get_info(matrix=matrix(1)%matrix, distribution=distri)
      CALL dbcsr_mp_grid_setup(distri)
      CALL dbcsr_distribution_get(distri, &
                                  group=group_handle, &
                                  mynode=control%myproc, &
                                  subgroups_defined=subgroups_defined, &
                                  pcol_group=pcol_handle)

      CALL control%mp_group%set_handle(group_handle)
      CALL control%pcol_group%set_handle(pcol_handle)

      IF (.NOT. subgroups_defined) &
         CPABORT("arnoldi only with subgroups")

      control%symmetric = .FALSE.
! Will need a fix for complex because there it has to be hermitian
      IF (SIZE(matrix) == 1) &
         control%symmetric = dbcsr_get_matrix_type(matrix(1)%matrix) == dbcsr_type_symmetric

! Set the control parameters
      control%max_iter = max_iter
      control%current_step = 0
      control%selection_crit = selection_crit
      control%nval_req = nval_request
      control%threshold = threshold
      control%converged = .FALSE.
      control%has_initial_vector = .FALSE.
      control%iram = iram
      control%nrestart = nrestarts
      control%generalized_ev = generalized_ev

      IF (control%nval_req > 1 .AND. control%nrestart > 0 .AND. .NOT. control%iram) &
         CALL cp_abort(__LOCATION__, 'with more than one eigenvalue requested '// &
                       'internal restarting with a previous EVEC is a bad idea, set IRAM or nrestsart=0')

! some checks for the generalized EV mode
      IF (control%generalized_ev .AND. selection_crit == 1) &
         CALL cp_abort(__LOCATION__, &
                       'generalized ev can only highest OR lowest EV')
      IF (control%generalized_ev .AND. nval_request .NE. 1) &
         CALL cp_abort(__LOCATION__, &
                       'generalized ev can only compute one EV at the time')
      IF (control%generalized_ev .AND. control%nrestart == 0) &
         CALL cp_abort(__LOCATION__, &
                       'outer loops are mandatory for generalized EV, set nrestart appropriatly')
      IF (SIZE(matrix) .NE. 2 .AND. control%generalized_ev) &
         CALL cp_abort(__LOCATION__, &
                       'generalized ev needs exactly two matrices as input (2nd is the metric)')

      ALLOCATE (control%selected_ind(max_iter))
      CALL set_control(arnoldi_data, control)

   END SUBROUTINE setup_arnoldi_control

! **************************************************************************************************
!> \brief Deallocate the data in arnoldi_data
!> \param arnoldi_data ...
!> \param ind ...
!> \param matrix ...
!> \param vector ...
! **************************************************************************************************
   SUBROUTINE get_selected_ritz_vector(arnoldi_data, ind, matrix, vector)
      TYPE(arnoldi_data_type)                            :: arnoldi_data
      INTEGER                                            :: ind
      TYPE(dbcsr_type)                                   :: matrix, vector

      IF (has_d_real(arnoldi_data)) CALL get_selected_ritz_vector_d(arnoldi_data, ind, matrix, vector)
      IF (has_d_cmplx(arnoldi_data)) CALL get_selected_ritz_vector_z(arnoldi_data, ind, matrix, vector)

   END SUBROUTINE get_selected_ritz_vector

! **************************************************************************************************
!> \brief Deallocate the data in arnoldi_data
!> \param arnoldi_data ...
! **************************************************************************************************
   SUBROUTINE deallocate_arnoldi_data(arnoldi_data)
      TYPE(arnoldi_data_type)                            :: arnoldi_data

      TYPE(arnoldi_control_type), POINTER                :: control

      IF (has_d_real(arnoldi_data)) CALL deallocate_arnoldi_data_d(arnoldi_data)
      IF (has_d_cmplx(arnoldi_data)) CALL deallocate_arnoldi_data_z(arnoldi_data)

      control => get_control(arnoldi_data)
      DEALLOCATE (control%selected_ind)
      DEALLOCATE (control)

   END SUBROUTINE deallocate_arnoldi_data

! **************************************************************************************************
!> \brief perform the selection of eigenvalues, fills the selected_ind array
!> \param arnoldi_data ...
! **************************************************************************************************
   SUBROUTINE select_evals(arnoldi_data)
      TYPE(arnoldi_data_type)                            :: arnoldi_data

      IF (has_d_real(arnoldi_data)) CALL select_evals_d(arnoldi_data)
      IF (has_d_cmplx(arnoldi_data)) CALL select_evals_z(arnoldi_data)

   END SUBROUTINE select_evals

! **************************************************************************************************
!> \brief set a new selection type, if you notice you didn't like the initial one
!> \param ar_data ...
!> \param itype ...
! **************************************************************************************************
   SUBROUTINE set_eval_selection(ar_data, itype)
      TYPE(arnoldi_data_type)                            :: ar_data
      INTEGER                                            :: itype

      TYPE(arnoldi_control_type), POINTER                :: control

      control => get_control(ar_data)
      control%selection_crit = itype
   END SUBROUTINE set_eval_selection

! **************************************************************************************************
!> \brief returns the number of restarts allowed for arnoldi
!> \param arnoldi_data ...
!> \return ...
! **************************************************************************************************
   FUNCTION get_nrestart(arnoldi_data) RESULT(nrestart)
      TYPE(arnoldi_data_type)                            :: arnoldi_data
      INTEGER                                            :: nrestart

      TYPE(arnoldi_control_type), POINTER                :: control

      control => get_control(arnoldi_data)
      nrestart = control%nrestart

   END FUNCTION get_nrestart

! **************************************************************************************************
!> \brief get the number of eigenvalues matching the search criterion
!> \param ar_data ...
!> \return ...
! **************************************************************************************************
   FUNCTION get_nval_out(ar_data) RESULT(nval_out)
      TYPE(arnoldi_data_type)                            :: ar_data
      INTEGER                                            :: nval_out

      TYPE(arnoldi_control_type), POINTER                :: control

      control => get_control(ar_data)
      nval_out = control%nval_out

   END FUNCTION get_nval_out

! **************************************************************************************************
!> \brief get the dimension of the krylov space. Can be less than max_iter
!>        if subspace converged early
!> \param ar_data ...
!> \return ...
! **************************************************************************************************
   FUNCTION get_subsp_size(ar_data) RESULT(current_step)
      TYPE(arnoldi_data_type)                            :: ar_data
      INTEGER                                            :: current_step

      TYPE(arnoldi_control_type), POINTER                :: control

      control => get_control(ar_data)
      current_step = control%current_step

   END FUNCTION get_subsp_size

! **************************************************************************************************
!> \brief Find out whether the method with the current search criterion is converged
!> \param ar_data ...
!> \return ...
! **************************************************************************************************
   FUNCTION arnoldi_is_converged(ar_data) RESULT(converged)
      TYPE(arnoldi_data_type)                            :: ar_data
      LOGICAL                                            :: converged

      TYPE(arnoldi_control_type), POINTER                :: control

      control => get_control(ar_data)
      converged = control%converged

   END FUNCTION

! **************************************************************************************************
!> \brief get a single specific Ritz value from the set of selected
!> \param ar_data ...
!> \param ind ...
!> \return ...
! **************************************************************************************************
   FUNCTION get_selected_ritz_val(ar_data, ind) RESULT(eval_out)
      TYPE(arnoldi_data_type)                            :: ar_data
      INTEGER                                            :: ind
      COMPLEX(real_8)                                    :: eval_out

      COMPLEX(real_8), DIMENSION(:), POINTER             :: evals_d
      INTEGER                                            :: ev_ind
      INTEGER, DIMENSION(:), POINTER                     :: selected_ind

      IF (ind .GT. get_nval_out(ar_data)) &
         CPABORT('outside range of indexed evals')

      selected_ind => get_sel_ind(ar_data)
      ev_ind = selected_ind(ind)
      IF (has_d_real(ar_data)) THEN
         evals_d => get_evals_d(ar_data); eval_out = evals_d(ev_ind)
      ELSE IF (has_d_cmplx(ar_data)) THEN
         evals_d => get_evals_z(ar_data); eval_out = evals_d(ev_ind)
      END IF

   END FUNCTION get_selected_ritz_val

! **************************************************************************************************
!> \brief Get all Ritz values of the selected set. eval_out has to be allocated
!>        at least the size of get_neval_out()
!> \param ar_data ...
!> \param eval_out ...
! **************************************************************************************************
   SUBROUTINE get_all_selected_ritz_val(ar_data, eval_out)
      TYPE(arnoldi_data_type)                            :: ar_data
      COMPLEX(real_8), DIMENSION(:)                      :: eval_out

      COMPLEX(real_8), DIMENSION(:), POINTER             :: evals_d
      INTEGER                                            :: ev_ind, ind
      INTEGER, DIMENSION(:), POINTER                     :: selected_ind

      NULLIFY (evals_d)
      IF (SIZE(eval_out) .LT. get_nval_out(ar_data)) &
         CPABORT('array for eval output too small')
      selected_ind => get_sel_ind(ar_data)

      IF (has_d_real(ar_data)) evals_d => get_evals_d(ar_data)
      IF (has_d_cmplx(ar_data)) evals_d => get_evals_d(ar_data)

      DO ind = 1, get_nval_out(ar_data)
         ev_ind = selected_ind(ind)
         IF (ASSOCIATED(evals_d)) eval_out(ind) = evals_d(ev_ind)
      END DO

   END SUBROUTINE get_all_selected_ritz_val

! **************************************************************************************************
!> \brief ...
!> \param ar_data ...
!> \param vector ...
! **************************************************************************************************
   SUBROUTINE set_arnoldi_initial_vector(ar_data, vector)
      TYPE(arnoldi_data_type)                            :: ar_data
      TYPE(dbcsr_type)                                   :: vector

      TYPE(arnoldi_control_type), POINTER                :: control

      control => get_control(ar_data)
      control%has_initial_vector = .TRUE.

      IF (has_d_real(ar_data)) CALL set_initial_vector_d(ar_data, vector)
      IF (has_d_cmplx(ar_data)) CALL set_initial_vector_z(ar_data, vector)

   END SUBROUTINE set_arnoldi_initial_vector

!!! Here come the methods handling the selection of eigenvalues and eigenvectors !!!
!!! If you want a personal method, simply created a Subroutine returning the index
!!! array selected ind which contains as the first nval_out entries the index of the evals

   #:include 'arnoldi.fypp'
   #:for nametype1, type_prec, real_zero, nametype_zero, type_nametype1, vartype in inst_params_1
! **************************************************************************************************
!> \brief ...
!> \param arnoldi_data ...
! **************************************************************************************************
      SUBROUTINE select_evals_${nametype1}$ (arnoldi_data)
         TYPE(arnoldi_data_type)                :: arnoldi_data

         INTEGER                                  :: my_crit, last_el, my_ind, i
         REAL(${type_prec}$)                        :: convergence
         TYPE(arnoldi_data_${nametype1}$_type), POINTER   :: ar_data
         TYPE(arnoldi_control_type), POINTER           :: control

         control => get_control(arnoldi_data)
         ar_data => get_data_${nametype1}$ (arnoldi_data)

         last_el = control%current_step
         convergence = REAL(0.0, ${type_prec}$)
         my_crit = control%selection_crit
         control%nval_out = MIN(control%nval_req, control%current_step)
         SELECT CASE (my_crit)
            ! minimum and maximum real eval
         CASE (1)
            CALL index_min_max_real_eval_${nametype1}$ (ar_data%evals, control%current_step, control%selected_ind, control%nval_out)
            ! n maximum real eval
         CASE (2)
            CALL index_nmax_real_eval_${nametype1}$ (ar_data%evals, control%current_step, control%selected_ind, control%nval_out)
            ! n minimum real eval
         CASE (3)
            CALL index_nmin_real_eval_${nametype1}$ (ar_data%evals, control%current_step, control%selected_ind, control%nval_out)
         CASE DEFAULT
            CPABORT("unknown selection index")
         END SELECT
         ! test whether we are converged
         DO i = 1, control%nval_out
            my_ind = control%selected_ind(i)
            convergence = MAX(convergence, &
                              ABS(ar_data%revec(last_el, my_ind)*ar_data%Hessenberg(last_el + 1, last_el)))
         END DO
         control%converged = convergence .LT. control%threshold

      END SUBROUTINE select_evals_${nametype1}$

! **************************************************************************************************
!> \brief ...
!> \param evals ...
!> \param current_step ...
!> \param selected_ind ...
!> \param neval ...
! **************************************************************************************************
      SUBROUTINE index_min_max_real_eval_${nametype1}$ (evals, current_step, selected_ind, neval)
         COMPLEX(${type_prec}$), DIMENSION(:)       :: evals
         INTEGER, INTENT(IN)                      :: current_step
         INTEGER, DIMENSION(:)                    :: selected_ind
         INTEGER                                  :: neval

         INTEGER, DIMENSION(current_step)         :: indexing
         REAL(${type_prec}$), DIMENSION(current_step)        :: tmp_array
         INTEGER                                   :: i

         neval = 0
         selected_ind = 0
         tmp_array(1:current_step) = REAL(evals(1:current_step), ${type_prec}$)
         CALL sort(tmp_array, current_step, indexing)
         DO i = 1, current_step
            IF (ABS(AIMAG(evals(indexing(i)))) < EPSILON(${real_zero}$)) THEN
               selected_ind(1) = indexing(i)
               neval = neval + 1
               EXIT
            END IF
         END DO
         DO i = current_step, 1, -1
            IF (ABS(AIMAG(evals(indexing(i)))) < EPSILON(${real_zero}$)) THEN
               selected_ind(2) = indexing(i)
               neval = neval + 1
               EXIT
            END IF
         END DO

      END SUBROUTINE index_min_max_real_eval_${nametype1}$

! **************************************************************************************************
!> \brief ...
!> \param evals ...
!> \param current_step ...
!> \param selected_ind ...
!> \param neval ...
! **************************************************************************************************
      SUBROUTINE index_nmax_real_eval_${nametype1}$ (evals, current_step, selected_ind, neval)
         COMPLEX(${type_prec}$), DIMENSION(:)       :: evals
         INTEGER, INTENT(IN)                      :: current_step
         INTEGER, DIMENSION(:)                    :: selected_ind
         INTEGER                                  :: neval

         INTEGER                                  :: i, nlimit
         INTEGER, DIMENSION(current_step)         :: indexing
         REAL(${type_prec}$), DIMENSION(current_step)        :: tmp_array

         nlimit = neval; neval = 0
         selected_ind = 0
         tmp_array(1:current_step) = REAL(evals(1:current_step), ${type_prec}$)
         CALL sort(tmp_array, current_step, indexing)
         DO i = 1, current_step
            IF (ABS(AIMAG(evals(indexing(current_step + 1 - i)))) < EPSILON(${real_zero}$)) THEN
               selected_ind(i) = indexing(current_step + 1 - i)
               neval = neval + 1
               IF (neval == nlimit) EXIT
            END IF
         END DO

      END SUBROUTINE index_nmax_real_eval_${nametype1}$

! **************************************************************************************************
!> \brief ...
!> \param evals ...
!> \param current_step ...
!> \param selected_ind ...
!> \param neval ...
! **************************************************************************************************
      SUBROUTINE index_nmin_real_eval_${nametype1}$ (evals, current_step, selected_ind, neval)
         COMPLEX(${type_prec}$), DIMENSION(:)       :: evals
         INTEGER, INTENT(IN)                      :: current_step
         INTEGER, DIMENSION(:)                    :: selected_ind
         INTEGER                                  :: neval, nlimit

         INTEGER                                  :: i
         INTEGER, DIMENSION(current_step)         :: indexing
         REAL(${type_prec}$), DIMENSION(current_step)        :: tmp_array

         nlimit = neval; neval = 0
         selected_ind = 0
         tmp_array(1:current_step) = REAL(evals(1:current_step), ${type_prec}$)
         CALL sort(tmp_array, current_step, indexing)
         DO i = 1, current_step
            IF (ABS(AIMAG(evals(indexing(i)))) < EPSILON(${real_zero}$)) THEN
               selected_ind(i) = indexing(i)
               neval = neval + 1
               IF (neval == nlimit) EXIT
            END IF
         END DO

      END SUBROUTINE index_nmin_real_eval_${nametype1}$

! **************************************************************************************************
!> \brief ...
!> \param arnoldi_data ...
!> \param matrix ...
!> \param max_iter ...
! **************************************************************************************************
      SUBROUTINE setup_arnoldi_data_${nametype1}$ (arnoldi_data, matrix, max_iter)
         TYPE(arnoldi_data_type)                 :: arnoldi_data
         TYPE(dbcsr_p_type), DIMENSION(:)     :: matrix
         INTEGER                                 :: max_iter

         INTEGER                                           :: nrow_local
         TYPE(arnoldi_data_${nametype1}$_type), POINTER      :: ar_data

         ALLOCATE (ar_data)
         CALL dbcsr_get_info(matrix=matrix(1)%matrix, nfullrows_local=nrow_local)
         ALLOCATE (ar_data%f_vec(nrow_local))
         ALLOCATE (ar_data%x_vec(nrow_local))
         ALLOCATE (ar_data%Hessenberg(max_iter + 1, max_iter))
         ALLOCATE (ar_data%local_history(nrow_local, max_iter))

         ALLOCATE (ar_data%evals(max_iter))
         ALLOCATE (ar_data%revec(max_iter, max_iter))

         CALL set_data_${nametype1}$ (arnoldi_data, ar_data)

      END SUBROUTINE setup_arnoldi_data_${nametype1}$

! **************************************************************************************************
!> \brief ...
!> \param arnoldi_data ...
! **************************************************************************************************
      SUBROUTINE deallocate_arnoldi_data_${nametype1}$ (arnoldi_data)
         TYPE(arnoldi_data_type)                     :: arnoldi_data

         TYPE(arnoldi_data_${nametype1}$_type), POINTER            :: ar_data

         ar_data => get_data_${nametype1}$ (arnoldi_data)
         IF (ASSOCIATED(ar_data%f_vec)) DEALLOCATE (ar_data%f_vec)
         IF (ASSOCIATED(ar_data%x_vec)) DEALLOCATE (ar_data%x_vec)
         IF (ASSOCIATED(ar_data%Hessenberg)) DEALLOCATE (ar_data%Hessenberg)
         IF (ASSOCIATED(ar_data%local_history)) DEALLOCATE (ar_data%local_history)
         IF (ASSOCIATED(ar_data%evals)) DEALLOCATE (ar_data%evals)
         IF (ASSOCIATED(ar_data%revec)) DEALLOCATE (ar_data%revec)
         DEALLOCATE (ar_data)

      END SUBROUTINE deallocate_arnoldi_data_${nametype1}$

! **************************************************************************************************
!> \brief ...
!> \param arnoldi_data ...
!> \param ind ...
!> \param matrix ...
!> \param vector ...
! **************************************************************************************************
      SUBROUTINE get_selected_ritz_vector_${nametype1}$ (arnoldi_data, ind, matrix, vector)
         TYPE(arnoldi_data_type)                 :: arnoldi_data
         INTEGER                                  :: ind
         TYPE(dbcsr_type)                          :: matrix
         TYPE(dbcsr_type)                          :: vector

         TYPE(arnoldi_data_${nametype1}$_type), POINTER      :: ar_data
         INTEGER                                           :: vsize, myind, sspace_size, i
         INTEGER, DIMENSION(:), POINTER           :: selected_ind
         COMPLEX(${type_prec}$), DIMENSION(:), ALLOCATABLE       :: ritz_v
         ${type_nametype1}$, DIMENSION(:), POINTER          :: data_vec
         TYPE(arnoldi_control_type), POINTER           :: control

         control => get_control(arnoldi_data)
         selected_ind => get_sel_ind(arnoldi_data)
         ar_data => get_data_${nametype1}$ (arnoldi_data)
         sspace_size = get_subsp_size(arnoldi_data)
         vsize = SIZE(ar_data%f_vec)
         myind = selected_ind(ind)
         ALLOCATE (ritz_v(vsize))
         ritz_v = CMPLX(0.0, 0.0, ${type_prec}$)

         CALL dbcsr_release(vector)
         CALL create_col_vec_from_matrix(vector, matrix, 1)
         IF (control%local_comp) THEN
            DO i = 1, sspace_size
               ritz_v(:) = ritz_v(:) + ar_data%local_history(:, i)*ar_data%revec(i, myind)
            END DO
            data_vec => dbcsr_get_data_p(vector, select_data_type=${nametype_zero}$)
            ! is a bit odd but ritz_v is always complex and matrix type determines where it goes
            ! again I hope the user knows what is required
            data_vec(1:vsize) = ${vartype}$ (ritz_v(1:vsize), KIND=${type_prec}$)
         END IF

         DEALLOCATE (ritz_v)

      END SUBROUTINE get_selected_ritz_vector_${nametype1}$

! **************************************************************************************************
!> \brief ...
!> \param arnoldi_data ...
!> \param vector ...
! **************************************************************************************************
      SUBROUTINE set_initial_vector_${nametype1}$ (arnoldi_data, vector)
         TYPE(arnoldi_data_type)                 :: arnoldi_data
         TYPE(dbcsr_type)                          :: vector

         TYPE(arnoldi_data_${nametype1}$_type), POINTER     :: ar_data
         ${type_nametype1}$, DIMENSION(:), POINTER          :: data_vec
         INTEGER                                           :: nrow_local, ncol_local
         TYPE(arnoldi_control_type), POINTER           :: control

         control => get_control(arnoldi_data)

         CALL dbcsr_get_info(matrix=vector, nfullrows_local=nrow_local, nfullcols_local=ncol_local)
         ar_data => get_data_${nametype1}$ (arnoldi_data)
         data_vec => dbcsr_get_data_p(vector, select_data_type=${nametype_zero}$)
         IF (nrow_local*ncol_local > 0) ar_data%f_vec(1:nrow_local) = data_vec(1:nrow_local)

      END SUBROUTINE set_initial_vector_${nametype1}$

   #:endfor

END MODULE arnoldi_data_methods

