LCOV - code coverage report
Current view: top level - src - qs_ot.F (source / functions) Hit Total Coverage
Test: CP2K Regtests (git:2fce0f8) Lines: 570 606 94.1 %
Date: 2024-12-21 06:28:57 Functions: 23 23 100.0 %

          Line data    Source code
       1             : !--------------------------------------------------------------------------------------------------!
       2             : !   CP2K: A general program to perform molecular dynamics simulations                              !
       3             : !   Copyright 2000-2024 CP2K developers group <https://cp2k.org>                                   !
       4             : !                                                                                                  !
       5             : !   SPDX-License-Identifier: GPL-2.0-or-later                                                      !
       6             : !--------------------------------------------------------------------------------------------------!
       7             : 
       8             : ! **************************************************************************************************
       9             : !> \brief orbital transformations
      10             : !> \par History
      11             : !>      Added Taylor expansion based computation of the matrix functions (01.2004)
      12             : !>      added additional rotation variables for non-equivalent occupied orbs (08.2004)
      13             : !> \author Joost VandeVondele (06.2002)
      14             : ! **************************************************************************************************
      15             : MODULE qs_ot
      16             :    USE arnoldi_api,                     ONLY: arnoldi_extremal
      17             :    USE cp_dbcsr_api,                    ONLY: &
      18             :         dbcsr_add, dbcsr_add_on_diag, dbcsr_copy, dbcsr_distribution_type, dbcsr_filter, &
      19             :         dbcsr_frobenius_norm, dbcsr_gershgorin_norm, dbcsr_get_block_p, dbcsr_get_info, &
      20             :         dbcsr_get_occupation, dbcsr_hadamard_product, dbcsr_init_p, dbcsr_iterator_blocks_left, &
      21             :         dbcsr_iterator_next_block, dbcsr_iterator_start, dbcsr_iterator_stop, dbcsr_iterator_type, &
      22             :         dbcsr_multiply, dbcsr_release, dbcsr_release_p, dbcsr_scale, dbcsr_scale_by_vector, &
      23             :         dbcsr_set, dbcsr_transposed, dbcsr_type
      24             :    USE cp_dbcsr_cholesky,               ONLY: cp_dbcsr_cholesky_decompose,&
      25             :                                               cp_dbcsr_cholesky_invert,&
      26             :                                               cp_dbcsr_cholesky_restore
      27             :    USE cp_dbcsr_diag,                   ONLY: cp_dbcsr_heevd,&
      28             :                                               cp_dbcsr_syevd
      29             :    USE kinds,                           ONLY: dp
      30             :    USE message_passing,                 ONLY: mp_comm_type
      31             :    USE preconditioner,                  ONLY: apply_preconditioner
      32             :    USE preconditioner_types,            ONLY: preconditioner_type
      33             :    USE qs_ot_types,                     ONLY: qs_ot_type
      34             : #include "./base/base_uses.f90"
      35             : 
      36             :    IMPLICIT NONE
      37             :    PRIVATE
      38             : 
      39             :    PUBLIC  :: qs_ot_get_p
      40             :    PUBLIC  :: qs_ot_get_orbitals
      41             :    PUBLIC  :: qs_ot_get_derivative
      42             :    PUBLIC  :: qs_ot_get_orbitals_ref
      43             :    PUBLIC  :: qs_ot_get_derivative_ref
      44             :    PUBLIC  :: qs_ot_new_preconditioner
      45             :    PRIVATE :: qs_ot_p2m_diag
      46             :    PRIVATE :: qs_ot_sinc
      47             :    PRIVATE :: qs_ot_ref_poly
      48             :    PRIVATE :: qs_ot_ref_chol
      49             :    PRIVATE :: qs_ot_ref_lwdn
      50             :    PRIVATE :: qs_ot_ref_decide
      51             :    PRIVATE :: qs_ot_ref_update
      52             :    PRIVATE :: qs_ot_refine
      53             :    PRIVATE :: qs_ot_on_the_fly_localize
      54             : 
      55             :    CHARACTER(len=*), PARAMETER, PRIVATE :: moduleN = 'qs_ot'
      56             : 
      57             : CONTAINS
      58             : 
      59             :    ! gets ready to use the preconditioner/ or renew the preconditioner
      60             :    ! only keeps a pointer to the preconditioner.
      61             :    ! If you change the preconditioner, you have to call this routine
      62             :    ! you remain responsible of proper deallocate of your preconditioner
      63             :    ! (or you can reuse it on the next step of the computation)
      64             : ! **************************************************************************************************
      65             : !> \brief ...
      66             : !> \param qs_ot_env ...
      67             : !> \param preconditioner ...
      68             : ! **************************************************************************************************
      69        7389 :    SUBROUTINE qs_ot_new_preconditioner(qs_ot_env, preconditioner)
      70             :       TYPE(qs_ot_type)                                   :: qs_ot_env
      71             :       TYPE(preconditioner_type), POINTER                 :: preconditioner
      72             : 
      73             :       INTEGER                                            :: ncoef
      74             : 
      75        7389 :       qs_ot_env%preconditioner => preconditioner
      76        7389 :       qs_ot_env%os_valid = .FALSE.
      77        7389 :       IF (.NOT. ASSOCIATED(qs_ot_env%matrix_psc0)) THEN
      78        7389 :          CALL dbcsr_init_p(qs_ot_env%matrix_psc0)
      79        7389 :          CALL dbcsr_copy(qs_ot_env%matrix_psc0, qs_ot_env%matrix_sc0, 'matrix_psc0')
      80             :       END IF
      81             : 
      82        7389 :       IF (.NOT. qs_ot_env%use_dx) THEN
      83        4147 :          qs_ot_env%use_dx = .TRUE.
      84        4147 :          CALL dbcsr_init_p(qs_ot_env%matrix_dx)
      85        4147 :          CALL dbcsr_copy(qs_ot_env%matrix_dx, qs_ot_env%matrix_gx, 'matrix_dx')
      86        4147 :          IF (qs_ot_env%settings%do_rotation) THEN
      87          30 :             CALL dbcsr_init_p(qs_ot_env%rot_mat_dx)
      88          30 :             CALL dbcsr_copy(qs_ot_env%rot_mat_dx, qs_ot_env%rot_mat_gx, 'rot_mat_dx')
      89             :          END IF
      90        4147 :          IF (qs_ot_env%settings%do_ener) THEN
      91           0 :             ncoef = SIZE(qs_ot_env%ener_gx)
      92           0 :             ALLOCATE (qs_ot_env%ener_dx(ncoef))
      93           0 :             qs_ot_env%ener_dx = 0.0_dp
      94             :          END IF
      95             :       END IF
      96             : 
      97        7389 :    END SUBROUTINE qs_ot_new_preconditioner
      98             : 
      99             : ! **************************************************************************************************
     100             : !> \brief ...
     101             : !> \param qs_ot_env ...
     102             : !> \param C_NEW ...
     103             : !> \param SC ...
     104             : !> \param G_OLD ...
     105             : !> \param D ...
     106             : ! **************************************************************************************************
     107         240 :    SUBROUTINE qs_ot_on_the_fly_localize(qs_ot_env, C_NEW, SC, G_OLD, D)
     108             :       !
     109             :       TYPE(qs_ot_type)                                   :: qs_ot_env
     110             :       TYPE(dbcsr_type), POINTER                          :: C_NEW, SC, G_OLD, D
     111             : 
     112             :       CHARACTER(len=*), PARAMETER :: routineN = 'qs_ot_on_the_fly_localize'
     113             :       INTEGER, PARAMETER                                 :: taylor_order = 50
     114             :       REAL(KIND=dp), PARAMETER                           :: alpha = 0.1_dp, f2_eps = 0.01_dp
     115             : 
     116             :       INTEGER                                            :: blk, col, col_size, group_handle, &
     117             :                                                             handle, i, k, n, p, row, row_size
     118          48 :       REAL(dp), DIMENSION(:, :), POINTER                 :: DATA
     119             :       REAL(KIND=dp)                                      :: expfactor, f2, norm_fro, norm_gct, tmp
     120             :       TYPE(dbcsr_distribution_type)                      :: dist
     121             :       TYPE(dbcsr_iterator_type)                          :: iter
     122             :       TYPE(dbcsr_type), POINTER                          :: C, Gp1, Gp2, GU, U
     123             :       TYPE(mp_comm_type)                                 :: group
     124             : 
     125          48 :       CALL timeset(routineN, handle)
     126             :       !
     127             :       !
     128          48 :       CALL dbcsr_get_info(C_NEW, nfullrows_total=n, nfullcols_total=k)
     129             :       !
     130             :       ! C = C*expm(-G)
     131          48 :       GU => qs_ot_env%buf1_k_k_nosym ! a buffer
     132          48 :       U => qs_ot_env%buf2_k_k_nosym ! a buffer
     133          48 :       Gp1 => qs_ot_env%buf3_k_k_nosym ! a buffer
     134          48 :       Gp2 => qs_ot_env%buf4_k_k_nosym ! a buffer
     135          48 :       C => qs_ot_env%buf1_n_k ! a buffer
     136             :       !
     137             :       ! compute the derivative of the norm
     138             :       !-------------------------------------------------------------------
     139             :       ! (x^2+eps)^1/2
     140          48 :       f2 = 0.0_dp
     141          48 :       CALL dbcsr_copy(C, C_NEW)
     142          48 :       CALL dbcsr_iterator_start(iter, C)
     143         104 :       DO WHILE (dbcsr_iterator_blocks_left(iter))
     144             :          CALL dbcsr_iterator_next_block(iter, row, col, DATA, blk, &
     145          56 :                                         row_size=row_size, col_size=col_size)
     146         392 :          DO p = 1, col_size ! p
     147        3576 :          DO i = 1, row_size ! i
     148        3232 :             tmp = SQRT(DATA(i, p)**2 + f2_eps)
     149        3232 :             f2 = f2 + tmp
     150        3520 :             DATA(i, p) = DATA(i, p)/tmp
     151             :          END DO
     152             :          END DO
     153             :       END DO
     154          48 :       CALL dbcsr_iterator_stop(iter)
     155          48 :       CALL dbcsr_get_info(C, group=group_handle)
     156          48 :       CALL group%set_handle(group_handle)
     157          48 :       CALL group%sum(f2)
     158             :       !
     159             :       !
     160          48 :       CALL dbcsr_multiply('T', 'N', 1.0_dp, C, C_NEW, 0.0_dp, GU)
     161             :       !
     162             :       ! antisymetrize
     163          48 :       CALL dbcsr_get_info(GU, distribution=dist)
     164             :       CALL dbcsr_transposed(U, GU, shallow_data_copy=.FALSE., &
     165             :                             use_distribution=dist, &
     166          48 :                             transpose_distribution=.FALSE.)
     167          48 :       CALL dbcsr_add(GU, U, alpha_scalar=-0.5_dp, beta_scalar=0.5_dp)
     168             :       !-------------------------------------------------------------------
     169             :       !
     170          48 :       norm_fro = dbcsr_frobenius_norm(GU)
     171          48 :       norm_gct = dbcsr_gershgorin_norm(GU)
     172             :       !write(*,*) 'qs_ot_localize: ||P-I||_f=',norm_fro,' ||P-I||_GCT=',norm_gct
     173             :       !
     174             :       !kscale = CEILING(LOG(MIN(norm_fro,norm_gct))/LOG(2.0_dp))
     175             :       !scale  = LOG(MIN(norm_fro,norm_gct))/LOG(2.0_dp)
     176             :       !write(*,*) 'qs_ot_localize: scale=',scale,' kscale=',kscale
     177             :       !
     178             :       ! rescale for steepest descent
     179          48 :       CALL dbcsr_scale(GU, -alpha)
     180             :       !
     181             :       ! compute unitary transform
     182             :       ! zeroth and first order
     183          48 :       expfactor = 1.0_dp
     184          48 :       CALL dbcsr_copy(U, GU)
     185          48 :       CALL dbcsr_scale(U, expfactor)
     186          48 :       CALL dbcsr_add_on_diag(U, 1.0_dp)
     187             :       ! other orders
     188          48 :       CALL dbcsr_copy(Gp1, GU)
     189         296 :       DO i = 2, taylor_order
     190             :          ! new power of G
     191         296 :          CALL dbcsr_multiply('N', 'N', 1.0_dp, GU, Gp1, 0.0_dp, Gp2)
     192         296 :          CALL dbcsr_copy(Gp1, Gp2)
     193             :          ! add to the taylor expansion so far
     194         296 :          expfactor = expfactor/REAL(i, KIND=dp)
     195         296 :          CALL dbcsr_add(U, Gp1, alpha_scalar=1.0_dp, beta_scalar=expfactor)
     196         296 :          norm_fro = dbcsr_frobenius_norm(Gp1)
     197             :          !write(*,*) 'Taylor expansion i=',i,' norm(X^i)/i!=',norm_fro*expfactor
     198         296 :          IF (norm_fro*expfactor .LT. 1.0E-10_dp) EXIT
     199             :       END DO
     200             :       !
     201             :       ! rotate MOs
     202          48 :       CALL dbcsr_multiply('N', 'N', 1.0_dp, C_NEW, U, 0.0_dp, C)
     203          48 :       CALL dbcsr_copy(C_NEW, C)
     204             :       !
     205             :       ! rotate SC
     206          48 :       CALL dbcsr_multiply('N', 'N', 1.0_dp, SC, U, 0.0_dp, C)
     207          48 :       CALL dbcsr_copy(SC, C)
     208             :       !
     209             :       ! rotate D_i
     210          48 :       CALL dbcsr_multiply('N', 'N', 1.0_dp, D, U, 0.0_dp, C)
     211          48 :       CALL dbcsr_copy(D, C)
     212             :       !
     213             :       ! rotate G_i-1
     214          48 :       IF (ASSOCIATED(G_OLD)) THEN
     215          48 :          CALL dbcsr_multiply('N', 'N', 1.0_dp, G_OLD, U, 0.0_dp, C)
     216          48 :          CALL dbcsr_copy(G_OLD, C)
     217             :       END IF
     218             :       !
     219          48 :       CALL timestop(handle)
     220          48 :    END SUBROUTINE qs_ot_on_the_fly_localize
     221             : 
     222             : ! **************************************************************************************************
     223             : !> \brief ...
     224             : !> \param qs_ot_env ...
     225             : !> \param C_OLD ...
     226             : !> \param C_TMP ...
     227             : !> \param C_NEW ...
     228             : !> \param P ...
     229             : !> \param SC ...
     230             : !> \param update ...
     231             : ! **************************************************************************************************
     232        1456 :    SUBROUTINE qs_ot_ref_chol(qs_ot_env, C_OLD, C_TMP, C_NEW, P, SC, update)
     233             :       !
     234             :       TYPE(qs_ot_type)                                   :: qs_ot_env
     235             :       TYPE(dbcsr_type)                                   :: C_OLD, C_TMP, C_NEW, P, SC
     236             :       LOGICAL, INTENT(IN)                                :: update
     237             : 
     238             :       CHARACTER(len=*), PARAMETER                        :: routineN = 'qs_ot_ref_chol'
     239             : 
     240             :       INTEGER                                            :: handle, k, n
     241             : 
     242         728 :       CALL timeset(routineN, handle)
     243             :       !
     244         728 :       CALL dbcsr_get_info(C_NEW, nfullrows_total=n, nfullcols_total=k)
     245             :       !
     246             :       ! P = U'*U
     247         728 :       CALL cp_dbcsr_cholesky_decompose(P, k, qs_ot_env%para_env, qs_ot_env%blacs_env)
     248             :       !
     249             :       ! C_NEW = C_OLD*inv(U)
     250             :       CALL cp_dbcsr_cholesky_restore(C_OLD, k, P, C_NEW, op="SOLVE", pos="RIGHT", &
     251         728 :                                      transa="N", para_env=qs_ot_env%para_env, blacs_env=qs_ot_env%blacs_env)
     252             :       !
     253             :       ! Update SC if needed
     254         728 :       IF (update) THEN
     255             :          CALL cp_dbcsr_cholesky_restore(SC, k, P, C_TMP, op="SOLVE", pos="RIGHT", &
     256         408 :                                         transa="N", para_env=qs_ot_env%para_env, blacs_env=qs_ot_env%blacs_env)
     257         408 :          CALL dbcsr_copy(SC, C_TMP)
     258             :       END IF
     259             :       !
     260         728 :       CALL timestop(handle)
     261         728 :    END SUBROUTINE qs_ot_ref_chol
     262             : 
     263             : ! **************************************************************************************************
     264             : !> \brief ...
     265             : !> \param qs_ot_env ...
     266             : !> \param C_OLD ...
     267             : !> \param C_TMP ...
     268             : !> \param C_NEW ...
     269             : !> \param P ...
     270             : !> \param SC ...
     271             : !> \param update ...
     272             : ! **************************************************************************************************
     273         240 :    SUBROUTINE qs_ot_ref_lwdn(qs_ot_env, C_OLD, C_TMP, C_NEW, P, SC, update)
     274             :       !
     275             :       TYPE(qs_ot_type)                                   :: qs_ot_env
     276             :       TYPE(dbcsr_type)                                   :: C_OLD, C_TMP, C_NEW, P, SC
     277             :       LOGICAL, INTENT(IN)                                :: update
     278             : 
     279             :       CHARACTER(len=*), PARAMETER                        :: routineN = 'qs_ot_ref_lwdn'
     280             : 
     281             :       INTEGER                                            :: handle, i, k, n
     282         240 :       REAL(dp), ALLOCATABLE, DIMENSION(:)                :: eig, fun
     283             :       TYPE(dbcsr_type), POINTER                          :: V, W
     284             : 
     285         240 :       CALL timeset(routineN, handle)
     286             :       !
     287         240 :       CALL dbcsr_get_info(C_NEW, nfullrows_total=n, nfullcols_total=k)
     288             :       !
     289         240 :       V => qs_ot_env%buf1_k_k_nosym ! a buffer
     290         240 :       W => qs_ot_env%buf2_k_k_nosym ! a buffer
     291         960 :       ALLOCATE (eig(k), fun(k))
     292             :       !
     293         240 :       CALL cp_dbcsr_syevd(P, V, eig, qs_ot_env%para_env, qs_ot_env%blacs_env)
     294             :       !
     295             :       ! compute the P^(-1/2)
     296        1408 :       DO i = 1, k
     297        1168 :          IF (eig(i) .LE. 0.0_dp) &
     298           0 :             CPABORT("P not positive definite")
     299        1408 :          IF (eig(i) .LT. 1.0E-8_dp) THEN
     300           0 :             fun(i) = 0.0_dp
     301             :          ELSE
     302        1168 :             fun(i) = 1.0_dp/SQRT(eig(i))
     303             :          END IF
     304             :       END DO
     305         240 :       CALL dbcsr_copy(W, V)
     306         240 :       CALL dbcsr_scale_by_vector(V, alpha=fun, side='right')
     307         240 :       CALL dbcsr_multiply('N', 'T', 1.0_dp, W, V, 0.0_dp, P)
     308             :       !
     309             :       ! Update C
     310         240 :       CALL dbcsr_multiply('N', 'N', 1.0_dp, C_OLD, P, 0.0_dp, C_NEW)
     311             :       !
     312             :       ! Update SC if needed
     313         240 :       IF (update) THEN
     314         188 :          CALL dbcsr_multiply('N', 'N', 1.0_dp, SC, P, 0.0_dp, C_TMP)
     315         188 :          CALL dbcsr_copy(SC, C_TMP)
     316             :       END IF
     317             :       !
     318         240 :       DEALLOCATE (eig, fun)
     319             :       !
     320         240 :       CALL timestop(handle)
     321         480 :    END SUBROUTINE qs_ot_ref_lwdn
     322             : 
     323             : ! **************************************************************************************************
     324             : !> \brief ...
     325             : !> \param qs_ot_env ...
     326             : !> \param C_OLD ...
     327             : !> \param C_TMP ...
     328             : !> \param C_NEW ...
     329             : !> \param P ...
     330             : !> \param SC ...
     331             : !> \param norm_in ...
     332             : !> \param update ...
     333             : ! **************************************************************************************************
     334        6808 :    SUBROUTINE qs_ot_ref_poly(qs_ot_env, C_OLD, C_TMP, C_NEW, P, SC, norm_in, update)
     335             :       !
     336             :       TYPE(qs_ot_type)                                   :: qs_ot_env
     337             :       TYPE(dbcsr_type), POINTER                          :: C_OLD, C_TMP, C_NEW, P
     338             :       TYPE(dbcsr_type)                                   :: SC
     339             :       REAL(dp), INTENT(IN)                               :: norm_in
     340             :       LOGICAL, INTENT(IN)                                :: update
     341             : 
     342             :       CHARACTER(len=*), PARAMETER                        :: routineN = 'qs_ot_ref_poly'
     343             : 
     344             :       INTEGER                                            :: handle, irefine, k, n
     345             :       LOGICAL                                            :: quick_exit
     346             :       REAL(dp)                                           :: norm, norm_fro, norm_gct, occ_in, &
     347             :                                                             occ_out, rescale
     348             :       TYPE(dbcsr_type), POINTER                          :: BUF1, BUF2, BUF_NOSYM, FT, FY
     349             : 
     350        3404 :       CALL timeset(routineN, handle)
     351             :       !
     352        3404 :       CALL dbcsr_get_info(C_NEW, nfullrows_total=n, nfullcols_total=k)
     353             :       !
     354        3404 :       BUF_NOSYM => qs_ot_env%buf1_k_k_nosym ! a buffer
     355        3404 :       BUF1 => qs_ot_env%buf1_k_k_sym ! a buffer
     356        3404 :       BUF2 => qs_ot_env%buf2_k_k_sym ! a buffer
     357        3404 :       FY => qs_ot_env%buf3_k_k_sym ! a buffer
     358        3404 :       FT => qs_ot_env%buf4_k_k_sym ! a buffer
     359             :       !
     360             :       ! initialize the norm (already computed in qs_ot_get_orbitals_ref)
     361        3404 :       norm = norm_in
     362             :       !
     363             :       ! can we do a quick exit?
     364        3404 :       quick_exit = .FALSE.
     365        3404 :       IF (norm .LT. qs_ot_env%settings%eps_irac_quick_exit) quick_exit = .TRUE.
     366             :       !
     367             :       ! lets refine
     368        3404 :       rescale = 1.0_dp
     369        3692 :       DO irefine = 1, qs_ot_env%settings%max_irac
     370             :          !
     371             :          ! rescaling
     372        3692 :          IF (norm .GT. 1.0_dp) THEN
     373          12 :             CALL dbcsr_scale(P, 1.0_dp/norm)
     374          12 :             rescale = rescale/SQRT(norm)
     375             :          END IF
     376             :          !
     377             :          ! get the refinement polynomial
     378             :          CALL qs_ot_refine(P, FY, BUF1, BUF2, qs_ot_env%settings%irac_degree, &
     379        3692 :                            qs_ot_env%settings%eps_irac_filter_matrix)
     380             :          !
     381             :          ! collect the transformation
     382        3692 :          IF (irefine .EQ. 1) THEN
     383        3404 :             CALL dbcsr_copy(FT, FY, name='FT')
     384             :          ELSE
     385         288 :             CALL dbcsr_multiply('N', 'N', 1.0_dp, FT, FY, 0.0_dp, BUF1)
     386         288 :             IF (qs_ot_env%settings%eps_irac_filter_matrix .GT. 0.0_dp) THEN
     387           4 :                occ_in = dbcsr_get_occupation(buf1)
     388           4 :                CALL dbcsr_filter(buf1, qs_ot_env%settings%eps_irac_filter_matrix)
     389           4 :                occ_out = dbcsr_get_occupation(buf1)
     390             :             END IF
     391         288 :             CALL dbcsr_copy(FT, BUF1, name='FT')
     392             :          END IF
     393             :          !
     394             :          ! quick exit if possible
     395        3692 :          IF (quick_exit) THEN
     396             :             EXIT
     397             :          END IF
     398             :          !
     399             :          ! P = FY^T * P * FY
     400        1460 :          CALL dbcsr_multiply('N', 'N', 1.0_dp, P, FY, 0.0_dp, BUF_NOSYM)
     401        1460 :          IF (qs_ot_env%settings%eps_irac_filter_matrix .GT. 0.0_dp) THEN
     402           8 :             occ_in = dbcsr_get_occupation(buf_nosym)
     403           8 :             CALL dbcsr_filter(buf_nosym, qs_ot_env%settings%eps_irac_filter_matrix)
     404           8 :             occ_out = dbcsr_get_occupation(buf_nosym)
     405             :          END IF
     406        1460 :          CALL dbcsr_multiply('N', 'N', 1.0_dp, FY, BUF_NOSYM, 0.0_dp, P)
     407        1460 :          IF (qs_ot_env%settings%eps_irac_filter_matrix .GT. 0.0_dp) THEN
     408           8 :             occ_in = dbcsr_get_occupation(p)
     409           8 :             CALL dbcsr_filter(p, qs_ot_env%settings%eps_irac_filter_matrix)
     410           8 :             occ_out = dbcsr_get_occupation(p)
     411             :          END IF
     412             :          !
     413             :          ! check ||P-1||_gct
     414        1460 :          CALL dbcsr_add_on_diag(P, -1.0_dp)
     415        1460 :          norm_fro = dbcsr_frobenius_norm(P)
     416        1460 :          norm_gct = dbcsr_gershgorin_norm(P)
     417        1460 :          CALL dbcsr_add_on_diag(P, 1.0_dp)
     418        1460 :          norm = MIN(norm_gct, norm_fro)
     419             :          !
     420             :          ! printing
     421             :          !
     422             :          ! blows up
     423        1460 :          IF (norm > 1.0E10_dp) THEN
     424             :             CALL cp_abort(__LOCATION__, &
     425             :                           "Refinement blows up! "// &
     426             :                           "We need you to improve the code, please post your input on "// &
     427           0 :                           "the forum https://www.cp2k.org/")
     428             :          END IF
     429             :          !
     430             :          ! can we do a quick exit next step?
     431        1460 :          IF (norm .LT. qs_ot_env%settings%eps_irac_quick_exit) quick_exit = .TRUE.
     432             :          !
     433             :          ! are we done?
     434        3692 :          IF (norm .LT. qs_ot_env%settings%eps_irac) EXIT
     435             :          !
     436             :       END DO
     437             :       !
     438             :       ! C_NEW = C_NEW * FT * rescale
     439        3404 :       CALL dbcsr_multiply('N', 'N', rescale, C_OLD, FT, 0.0_dp, C_NEW)
     440        3404 :       IF (qs_ot_env%settings%eps_irac_filter_matrix .GT. 0.0_dp) THEN
     441           4 :          occ_in = dbcsr_get_occupation(c_new)
     442           4 :          CALL dbcsr_filter(c_new, qs_ot_env%settings%eps_irac_filter_matrix)
     443           4 :          occ_out = dbcsr_get_occupation(c_new)
     444             :       END IF
     445             :       !
     446             :       ! update SC = SC * FY * rescale
     447        3404 :       IF (update) THEN
     448        1356 :          CALL dbcsr_multiply('N', 'N', rescale, SC, FT, 0.0_dp, C_TMP)
     449        1356 :          IF (qs_ot_env%settings%eps_irac_filter_matrix .GT. 0.0_dp) THEN
     450           4 :             occ_in = dbcsr_get_occupation(c_tmp)
     451           4 :             CALL dbcsr_filter(c_tmp, qs_ot_env%settings%eps_irac_filter_matrix)
     452           4 :             occ_out = dbcsr_get_occupation(c_tmp)
     453             :          END IF
     454        1356 :          CALL dbcsr_copy(SC, C_TMP)
     455             :       END IF
     456             :       !
     457        3404 :       CALL timestop(handle)
     458        3404 :    END SUBROUTINE qs_ot_ref_poly
     459             : 
     460             : ! **************************************************************************************************
     461             : !> \brief ...
     462             : !> \param qs_ot_env1 ...
     463             : !> \return ...
     464             : ! **************************************************************************************************
     465        4372 :    FUNCTION qs_ot_ref_update(qs_ot_env1) RESULT(update)
     466             :       !
     467             :       TYPE(qs_ot_type)                                   :: qs_ot_env1
     468             :       LOGICAL                                            :: update
     469             : 
     470        4372 :       update = .FALSE.
     471        3940 :       SELECT CASE (qs_ot_env1%settings%ot_method)
     472             :       CASE ("CG")
     473        3940 :          SELECT CASE (qs_ot_env1%settings%line_search_method)
     474             :          CASE ("2PNT")
     475        3940 :             IF (qs_ot_env1%line_search_count .EQ. 2) update = .TRUE.
     476             :          CASE DEFAULT
     477        3940 :             CPABORT("NYI")
     478             :          END SELECT
     479             :       CASE ("DIIS")
     480           0 :          update = .TRUE.
     481             :       CASE DEFAULT
     482        4372 :          CPABORT("NYI")
     483             :       END SELECT
     484        4372 :    END FUNCTION qs_ot_ref_update
     485             : 
     486             : ! **************************************************************************************************
     487             : !> \brief ...
     488             : !> \param qs_ot_env1 ...
     489             : !> \param norm_in ...
     490             : !> \param ortho_irac ...
     491             : ! **************************************************************************************************
     492        4372 :    SUBROUTINE qs_ot_ref_decide(qs_ot_env1, norm_in, ortho_irac)
     493             :       !
     494             :       TYPE(qs_ot_type)                                   :: qs_ot_env1
     495             :       REAL(dp), INTENT(IN)                               :: norm_in
     496             :       CHARACTER(LEN=*), INTENT(INOUT)                    :: ortho_irac
     497             : 
     498        4372 :       ortho_irac = qs_ot_env1%settings%ortho_irac
     499        4372 :       IF (norm_in .LT. qs_ot_env1%settings%eps_irac_switch) ortho_irac = "POLY"
     500        4372 :    END SUBROUTINE qs_ot_ref_decide
     501             : 
     502             : ! **************************************************************************************************
     503             : !> \brief ...
     504             : !> \param matrix_c ...
     505             : !> \param matrix_s ...
     506             : !> \param matrix_x ...
     507             : !> \param matrix_sx ...
     508             : !> \param matrix_gx_old ...
     509             : !> \param matrix_dx ...
     510             : !> \param qs_ot_env ...
     511             : !> \param qs_ot_env1 ...
     512             : ! **************************************************************************************************
     513        8744 :    SUBROUTINE qs_ot_get_orbitals_ref(matrix_c, matrix_s, matrix_x, matrix_sx, &
     514             :                                      matrix_gx_old, matrix_dx, qs_ot_env, qs_ot_env1)
     515             :       !
     516             :       TYPE(dbcsr_type), POINTER                          :: matrix_c, matrix_s, matrix_x, matrix_sx, &
     517             :                                                             matrix_gx_old, matrix_dx
     518             :       TYPE(qs_ot_type)                                   :: qs_ot_env, qs_ot_env1
     519             : 
     520             :       CHARACTER(len=*), PARAMETER :: routineN = 'qs_ot_get_orbitals_ref'
     521             : 
     522             :       CHARACTER(LEN=4)                                   :: ortho_irac
     523             :       INTEGER                                            :: handle, k, n
     524             :       LOGICAL                                            :: on_the_fly_loc, update
     525             :       REAL(dp)                                           :: norm, norm_fro, norm_gct, occ_in, occ_out
     526             :       TYPE(dbcsr_type), POINTER                          :: C_NEW, C_OLD, C_TMP, D, G_OLD, P, S, SC
     527             : 
     528        4372 :       CALL timeset(routineN, handle)
     529             : 
     530        4372 :       CALL dbcsr_get_info(matrix_c, nfullrows_total=n, nfullcols_total=k)
     531             :       !
     532        4372 :       C_NEW => matrix_c
     533        4372 :       C_OLD => matrix_x ! need to be carefully updated for the gradient !
     534        4372 :       SC => matrix_sx ! need to be carefully updated for the gradient !
     535        4372 :       G_OLD => matrix_gx_old ! need to be carefully updated for localization !
     536        4372 :       D => matrix_dx ! need to be carefully updated for localization !
     537        4372 :       S => matrix_s
     538             : 
     539        4372 :       P => qs_ot_env%p_k_k_sym ! a buffer
     540        4372 :       C_TMP => qs_ot_env%buf1_n_k ! a buffer
     541             :       !
     542             :       ! do we need to update C_OLD and SC?
     543        4372 :       update = qs_ot_ref_update(qs_ot_env1)
     544             :       !
     545             :       ! do we want to on the fly localize?
     546             :       ! for the moment this is set from the input,
     547             :       ! later we might want to localize every n-step or
     548             :       ! when the sparsity increases...
     549        4372 :       on_the_fly_loc = qs_ot_env1%settings%on_the_fly_loc
     550             :       !
     551             :       ! compute SC = S*C
     552        4372 :       IF (ASSOCIATED(S)) THEN
     553        4372 :          CALL dbcsr_multiply('N', 'N', 1.0_dp, S, C_OLD, 0.0_dp, SC)
     554        4372 :          IF (qs_ot_env1%settings%eps_irac_filter_matrix .GT. 0.0_dp) THEN
     555           4 :             occ_in = dbcsr_get_occupation(sc)
     556           4 :             CALL dbcsr_filter(sc, qs_ot_env1%settings%eps_irac_filter_matrix)
     557           4 :             occ_out = dbcsr_get_occupation(sc)
     558             :          END IF
     559             :       ELSE
     560           0 :          CALL dbcsr_copy(SC, C_OLD)
     561             :       END IF
     562             :       !
     563             :       ! compute P = C'*SC
     564        4372 :       CALL dbcsr_multiply('T', 'N', 1.0_dp, C_OLD, SC, 0.0_dp, P)
     565        4372 :       IF (qs_ot_env1%settings%eps_irac_filter_matrix .GT. 0.0_dp) THEN
     566           4 :          occ_in = dbcsr_get_occupation(p)
     567           4 :          CALL dbcsr_filter(p, qs_ot_env1%settings%eps_irac_filter_matrix)
     568           4 :          occ_out = dbcsr_get_occupation(p)
     569             :       END IF
     570             :       !
     571             :       ! check ||P-1||_f and ||P-1||_gct
     572        4372 :       CALL dbcsr_add_on_diag(P, -1.0_dp)
     573        4372 :       norm_fro = dbcsr_frobenius_norm(P)
     574        4372 :       norm_gct = dbcsr_gershgorin_norm(P)
     575        4372 :       CALL dbcsr_add_on_diag(P, 1.0_dp)
     576        4372 :       norm = MIN(norm_gct, norm_fro)
     577        4372 :       CALL qs_ot_ref_decide(qs_ot_env1, norm, ortho_irac)
     578             :       !
     579             :       ! select the orthogonality method
     580         728 :       SELECT CASE (ortho_irac)
     581             :       CASE ("CHOL")
     582         728 :          CALL qs_ot_ref_chol(qs_ot_env, C_OLD, C_TMP, C_NEW, P, SC, update)
     583             :       CASE ("LWDN")
     584         240 :          CALL qs_ot_ref_lwdn(qs_ot_env, C_OLD, C_TMP, C_NEW, P, SC, update)
     585             :       CASE ("POLY")
     586        3404 :          CALL qs_ot_ref_poly(qs_ot_env, C_OLD, C_TMP, C_NEW, P, SC, norm, update)
     587             :       CASE DEFAULT
     588        4372 :          CPABORT("Wrong argument")
     589             :       END SELECT
     590             :       !
     591             :       ! We update the C_i+1 and localization
     592        4372 :       IF (update) THEN
     593        1952 :          IF (on_the_fly_loc) THEN
     594          48 :             CALL qs_ot_on_the_fly_localize(qs_ot_env, C_NEW, SC, G_OLD, D)
     595             :          END IF
     596        1952 :          CALL dbcsr_copy(C_OLD, C_NEW)
     597             :       END IF
     598             :       !
     599        4372 :       CALL timestop(handle)
     600        4372 :    END SUBROUTINE qs_ot_get_orbitals_ref
     601             : 
     602             : ! **************************************************************************************************
     603             : !> \brief ...
     604             : !> \param P ...
     605             : !> \param FY ...
     606             : !> \param P2 ...
     607             : !> \param T ...
     608             : !> \param irac_degree ...
     609             : !> \param eps_irac_filter_matrix ...
     610             : ! **************************************************************************************************
     611        7384 :    SUBROUTINE qs_ot_refine(P, FY, P2, T, irac_degree, eps_irac_filter_matrix)
     612             :       !----------------------------------------------------------------------
     613             :       ! refinement polynomial of degree 2,3 and 4 (PRB 70, 193102 (2004))
     614             :       !----------------------------------------------------------------------
     615             : 
     616             :       TYPE(dbcsr_type), INTENT(inout)                    :: P, FY, P2, T
     617             :       INTEGER, INTENT(in)                                :: irac_degree
     618             :       REAL(dp), INTENT(in)                               :: eps_irac_filter_matrix
     619             : 
     620             :       CHARACTER(len=*), PARAMETER                        :: routineN = 'qs_ot_refine'
     621             : 
     622             :       INTEGER                                            :: handle, k
     623             :       REAL(dp)                                           :: occ_in, occ_out, r
     624             : 
     625        3692 :       CALL timeset(routineN, handle)
     626             : 
     627        3692 :       CALL dbcsr_get_info(P, nfullcols_total=k)
     628        3692 :       SELECT CASE (irac_degree)
     629             :       CASE (2)
     630             :          ! C_out = C_in * ( 15/8 * I - 10/8 * P + 3/8 * P^2)
     631           0 :          r = 3.0_dp/8.0_dp
     632           0 :          CALL dbcsr_multiply('N', 'N', r, P, P, 0.0_dp, FY)
     633           0 :          IF (eps_irac_filter_matrix .GT. 0.0_dp) THEN
     634           0 :             occ_in = dbcsr_get_occupation(fy)
     635           0 :             CALL dbcsr_filter(fy, eps_irac_filter_matrix)
     636           0 :             occ_out = dbcsr_get_occupation(fy)
     637             :          END IF
     638           0 :          r = -10.0_dp/8.0_dp
     639           0 :          CALL dbcsr_add(FY, P, alpha_scalar=1.0_dp, beta_scalar=r)
     640           0 :          r = 15.0_dp/8.0_dp
     641           0 :          CALL dbcsr_add_on_diag(FY, alpha_scalar=r)
     642             :       CASE (3)
     643             :          ! C_out = C_in * ( 35/16 * I - 35/16 * P + 21/16 * P^2 - 5/16 P^3)
     644           0 :          CALL dbcsr_multiply('N', 'N', 1.0_dp, P, P, 0.0_dp, P2)
     645           0 :          IF (eps_irac_filter_matrix .GT. 0.0_dp) THEN
     646           0 :             occ_in = dbcsr_get_occupation(p2)
     647           0 :             CALL dbcsr_filter(p2, eps_irac_filter_matrix)
     648           0 :             occ_out = dbcsr_get_occupation(p2)
     649             :          END IF
     650           0 :          r = -5.0_dp/16.0_dp
     651           0 :          CALL dbcsr_multiply('N', 'N', r, P2, P, 0.0_dp, FY)
     652           0 :          IF (eps_irac_filter_matrix .GT. 0.0_dp) THEN
     653           0 :             occ_in = dbcsr_get_occupation(fy)
     654           0 :             CALL dbcsr_filter(fy, eps_irac_filter_matrix)
     655           0 :             occ_out = dbcsr_get_occupation(fy)
     656             :          END IF
     657           0 :          r = 21.0_dp/16.0_dp
     658           0 :          CALL dbcsr_add(FY, P2, alpha_scalar=1.0_dp, beta_scalar=r)
     659           0 :          r = -35.0_dp/16.0_dp
     660           0 :          CALL dbcsr_add(FY, P, alpha_scalar=1.0_dp, beta_scalar=r)
     661           0 :          r = 35.0_dp/16.0_dp
     662           0 :          CALL dbcsr_add_on_diag(FY, alpha_scalar=r)
     663             :       CASE (4)
     664             :          ! C_out = C_in * ( 315/128 * I - 420/128 * P + 378/128 * P^2 - 180/128 P^3 + 35/128 P^4 )
     665             :          !       = C_in * ( 315/128 * I - 420/128 * P + 378/128 * P^2 + ( - 180/128 * P + 35/128 * P^2 ) * P^2 )
     666        3692 :          CALL dbcsr_multiply('N', 'N', 1.0_dp, P, P, 0.0_dp, P2) ! P^2
     667        3692 :          IF (eps_irac_filter_matrix .GT. 0.0_dp) THEN
     668           8 :             occ_in = dbcsr_get_occupation(p2)
     669           8 :             CALL dbcsr_filter(p2, eps_irac_filter_matrix)
     670           8 :             occ_out = dbcsr_get_occupation(p2)
     671             :          END IF
     672        3692 :          r = -180.0_dp/128.0_dp
     673        3692 :          CALL dbcsr_add(T, P, alpha_scalar=0.0_dp, beta_scalar=r) ! T=-180/128*P
     674        3692 :          r = 35.0_dp/128.0_dp
     675        3692 :          CALL dbcsr_add(T, P2, alpha_scalar=1.0_dp, beta_scalar=r) ! T=T+35/128*P^2
     676        3692 :          CALL dbcsr_multiply('N', 'N', 1.0_dp, T, P2, 0.0_dp, FY) ! Y=T*P^2
     677        3692 :          IF (eps_irac_filter_matrix .GT. 0.0_dp) THEN
     678           8 :             occ_in = dbcsr_get_occupation(fy)
     679           8 :             CALL dbcsr_filter(fy, eps_irac_filter_matrix)
     680           8 :             occ_out = dbcsr_get_occupation(fy)
     681             :          END IF
     682        3692 :          r = 378.0_dp/128.0_dp
     683        3692 :          CALL dbcsr_add(FY, P2, alpha_scalar=1.0_dp, beta_scalar=r) ! Y=Y+378/128*P^2
     684        3692 :          r = -420.0_dp/128.0_dp
     685        3692 :          CALL dbcsr_add(FY, P, alpha_scalar=1.0_dp, beta_scalar=r) ! Y=Y-420/128*P
     686        3692 :          r = 315.0_dp/128.0_dp
     687        3692 :          CALL dbcsr_add_on_diag(FY, alpha_scalar=r) ! Y=Y+315/128*I
     688             :       CASE DEFAULT
     689        3692 :          CPABORT("This irac_order NYI")
     690             :       END SELECT
     691        3692 :       CALL timestop(handle)
     692        3692 :    END SUBROUTINE qs_ot_refine
     693             : 
     694             : ! **************************************************************************************************
     695             : !> \brief ...
     696             : !> \param matrix_hc ...
     697             : !> \param matrix_x ...
     698             : !> \param matrix_sx ...
     699             : !> \param matrix_gx ...
     700             : !> \param qs_ot_env ...
     701             : ! **************************************************************************************************
     702        5704 :    SUBROUTINE qs_ot_get_derivative_ref(matrix_hc, matrix_x, matrix_sx, matrix_gx, &
     703             :                                        qs_ot_env)
     704             :       TYPE(dbcsr_type), POINTER                          :: matrix_hc, matrix_x, matrix_sx, matrix_gx
     705             :       TYPE(qs_ot_type)                                   :: qs_ot_env
     706             : 
     707             :       CHARACTER(len=*), PARAMETER :: routineN = 'qs_ot_get_derivative_ref'
     708             : 
     709             :       INTEGER                                            :: handle, k, n
     710             :       REAL(dp)                                           :: occ_in, occ_out
     711             :       TYPE(dbcsr_type), POINTER                          :: C, CHC, G, G_dp, HC, SC
     712             : 
     713        2852 :       CALL timeset(routineN, handle)
     714             : 
     715        2852 :       CALL dbcsr_get_info(matrix_x, nfullrows_total=n, nfullcols_total=k)
     716             :       !
     717        2852 :       C => matrix_x ! NBsf*NOcc
     718        2852 :       SC => matrix_sx ! NBsf*NOcc need to be up2date
     719        2852 :       HC => matrix_hc ! NBsf*NOcc
     720        2852 :       G => matrix_gx ! NBsf*NOcc
     721        2852 :       CHC => qs_ot_env%buf1_k_k_sym ! buffer
     722        2852 :       G_dp => qs_ot_env%buf1_n_k_dp ! buffer dp
     723             : 
     724             :       ! C'*(H*C)
     725        2852 :       CALL dbcsr_multiply('T', 'N', 1.0_dp, C, HC, 0.0_dp, CHC)
     726        2852 :       IF (qs_ot_env%settings%eps_irac_filter_matrix .GT. 0.0_dp) THEN
     727           4 :          occ_in = dbcsr_get_occupation(chc)
     728           4 :          CALL dbcsr_filter(chc, qs_ot_env%settings%eps_irac_filter_matrix)
     729           4 :          occ_out = dbcsr_get_occupation(chc)
     730             :       END IF
     731             :       ! (S*C)*(C'*H*C)
     732        2852 :       CALL dbcsr_multiply('N', 'N', 1.0_dp, SC, CHC, 0.0_dp, G)
     733        2852 :       IF (qs_ot_env%settings%eps_irac_filter_matrix .GT. 0.0_dp) THEN
     734           4 :          occ_in = dbcsr_get_occupation(g)
     735           4 :          CALL dbcsr_filter(g, qs_ot_env%settings%eps_irac_filter_matrix)
     736           4 :          occ_out = dbcsr_get_occupation(g)
     737             :       END IF
     738             :       ! G = 2*(1-S*C*C')*H*C
     739        2852 :       CALL dbcsr_add(G, HC, alpha_scalar=-1.0_dp, beta_scalar=1.0_dp)
     740             :       !
     741        2852 :       CALL timestop(handle)
     742        2852 :    END SUBROUTINE qs_ot_get_derivative_ref
     743             : 
     744             :    ! computes p=x*S*x and the matrix functionals related matrices
     745             : ! **************************************************************************************************
     746             : !> \brief ...
     747             : !> \param matrix_x ...
     748             : !> \param matrix_sx ...
     749             : !> \param qs_ot_env ...
     750             : ! **************************************************************************************************
     751      269145 :    SUBROUTINE qs_ot_get_p(matrix_x, matrix_sx, qs_ot_env)
     752             : 
     753             :       TYPE(dbcsr_type), POINTER                          :: matrix_x, matrix_sx
     754             :       TYPE(qs_ot_type)                                   :: qs_ot_env
     755             : 
     756             :       CHARACTER(len=*), PARAMETER                        :: routineN = 'qs_ot_get_p'
     757             :       REAL(KIND=dp), PARAMETER                           :: rone = 1.0_dp, rzero = 0.0_dp
     758             : 
     759             :       INTEGER                                            :: handle, k, max_iter, n
     760             :       LOGICAL                                            :: converged
     761             :       REAL(KIND=dp)                                      :: max_ev, min_ev, threshold
     762             : 
     763       89715 :       CALL timeset(routineN, handle)
     764             : 
     765       89715 :       CALL dbcsr_get_info(matrix_x, nfullrows_total=n, nfullcols_total=k)
     766             : 
     767             :       ! get the overlap
     768             :       CALL dbcsr_multiply('T', 'N', rone, matrix_x, matrix_sx, rzero, &
     769       89715 :                           qs_ot_env%matrix_p)
     770             : 
     771             :       ! get an upper bound for the largest eigenvalue
     772             :       ! try using lancos first and fall back to gershgorin norm if it fails
     773       89715 :       max_iter = 30; threshold = 1.0E-03_dp
     774       89715 :       CALL arnoldi_extremal(qs_ot_env%matrix_p, max_ev, min_ev, converged, threshold, max_iter)
     775       89715 :       qs_ot_env%largest_eval_upper_bound = MAX(max_ev, ABS(min_ev))
     776             : 
     777       89715 :       IF (.NOT. converged) qs_ot_env%largest_eval_upper_bound = dbcsr_gershgorin_norm(qs_ot_env%matrix_p)
     778       89715 :       CALL decide_strategy(qs_ot_env)
     779       89715 :       IF (qs_ot_env%do_taylor) THEN
     780       49992 :          CALL qs_ot_p2m_taylor(qs_ot_env)
     781             :       ELSE
     782       39723 :          CALL qs_ot_p2m_diag(qs_ot_env)
     783             :       END IF
     784             : 
     785       89715 :       IF (qs_ot_env%settings%do_rotation) THEN
     786        2590 :          CALL qs_ot_generate_rotation(qs_ot_env)
     787             :       END IF
     788             : 
     789       89715 :       CALL timestop(handle)
     790             : 
     791       89715 :    END SUBROUTINE qs_ot_get_p
     792             : 
     793             : ! **************************************************************************************************
     794             : !> \brief computes the rotation matrix rot_mat_u that is associated to a given
     795             : !>      rot_mat_x using rot_mat_u=exp(rot_mat_x)
     796             : !> \param qs_ot_env a valid qs_ot_env
     797             : !> \par History
     798             : !>      08.2004 created [Joost VandeVondele]
     799             : ! **************************************************************************************************
     800        2590 :    SUBROUTINE qs_ot_generate_rotation(qs_ot_env)
     801             : 
     802             :       TYPE(qs_ot_type)                                   :: qs_ot_env
     803             : 
     804             :       CHARACTER(len=*), PARAMETER :: routineN = 'qs_ot_generate_rotation'
     805             :       COMPLEX(KIND=dp), PARAMETER                        :: cone = (1.0_dp, 0.0_dp), &
     806             :                                                             czero = (0.0_dp, 0.0_dp)
     807             : 
     808        2590 :       COMPLEX(KIND=dp), ALLOCATABLE, DIMENSION(:)        :: evals_exp
     809        2590 :       COMPLEX(KIND=dp), DIMENSION(:), POINTER            :: data_z
     810             :       INTEGER                                            :: blk, col, handle, k, row
     811             :       LOGICAL                                            :: found
     812        2590 :       REAL(KIND=dp), DIMENSION(:), POINTER               :: data_d
     813             :       TYPE(dbcsr_iterator_type)                          :: iter
     814             :       TYPE(dbcsr_type)                                   :: cmat_u, cmat_x
     815             : 
     816        2590 :       CALL timeset(routineN, handle)
     817             : 
     818        2590 :       CALL dbcsr_get_info(qs_ot_env%rot_mat_x, nfullrows_total=k)
     819             : 
     820        2590 :       IF (k /= 0) THEN
     821        2538 :          CALL dbcsr_copy(cmat_x, qs_ot_env%rot_mat_evec, name='cmat_x')
     822        2538 :          CALL dbcsr_copy(cmat_u, qs_ot_env%rot_mat_evec, name='cmat_u')
     823        7614 :          ALLOCATE (evals_exp(k))
     824             : 
     825             :          ! rot_mat_u = exp(rot_mat_x)
     826             :          ! i rot_mat_x is hermitian, so go over the complex variables for diag
     827             :          !vwCALL cp_cfm_get_info(cmat_x,local_data=local_data_c)
     828             :          !vwCALL cp_fm_get_info(qs_ot_env%rot_mat_x,local_data=local_data_r)
     829             :          !vwlocal_data_c=CMPLX(0.0_dp,local_data_r,KIND=dp)
     830        2538 :          CALL dbcsr_iterator_start(iter, cmat_x)
     831        3698 :          DO WHILE (dbcsr_iterator_blocks_left(iter))
     832        1160 :             CALL dbcsr_iterator_next_block(iter, row, col, data_z, blk)
     833        1160 :             CALL dbcsr_get_block_p(qs_ot_env%rot_mat_x, row, col, data_d, found)
     834        3698 :             IF (.NOT. found) THEN
     835           0 :                WRITE (*, *) routineN//' .NOT.found'
     836             :                !stop
     837             :             ELSE
     838       25960 :                data_z = CMPLX(0.0_dp, data_d, KIND=dp)
     839             :             END IF
     840             :          END DO
     841        2538 :          CALL dbcsr_iterator_stop(iter)
     842             : 
     843             :          CALL cp_dbcsr_heevd(cmat_x, qs_ot_env%rot_mat_evec, qs_ot_env%rot_mat_evals, &
     844        2538 :                              qs_ot_env%para_env, qs_ot_env%blacs_env)
     845       12830 :          evals_exp(:) = EXP((0.0_dp, -1.0_dp)*qs_ot_env%rot_mat_evals(:))
     846        2538 :          CALL dbcsr_copy(cmat_x, qs_ot_env%rot_mat_evec)
     847        2538 :          CALL dbcsr_scale_by_vector(cmat_x, alpha=evals_exp, side='right')
     848        2538 :          CALL dbcsr_multiply('N', 'C', cone, cmat_x, qs_ot_env%rot_mat_evec, czero, cmat_u)
     849        2538 :          CALL dbcsr_copy(qs_ot_env%rot_mat_u, cmat_u, keep_imaginary=.FALSE.)
     850        2538 :          CALL dbcsr_release(cmat_x)
     851        2538 :          CALL dbcsr_release(cmat_u)
     852        5076 :          DEALLOCATE (evals_exp)
     853             :       END IF
     854             : 
     855        2590 :       CALL timestop(handle)
     856             : 
     857        5180 :    END SUBROUTINE qs_ot_generate_rotation
     858             : 
     859             : ! **************************************************************************************************
     860             : !> \brief computes the derivative fields with respect to rot_mat_x
     861             : !> \param qs_ot_env valid qs_ot_env. In particular qs_ot_generate_rotation has to be called before
     862             : !>                        and the rot_mat_dedu matrix has to be up to date
     863             : !> \par History
     864             : !>      08.2004 created [ Joost VandeVondele ]
     865             : ! **************************************************************************************************
     866        2768 :    SUBROUTINE qs_ot_rot_mat_derivative(qs_ot_env)
     867             :       TYPE(qs_ot_type)                         :: qs_ot_env
     868             : 
     869             :       CHARACTER(len=*), PARAMETER :: routineN = 'qs_ot_rot_mat_derivative'
     870             : 
     871             :       COMPLEX(KIND=dp), PARAMETER              :: cone = (1.0_dp, 0.0_dp), &
     872             :                                                   czero = (0.0_dp, 0.0_dp)
     873             : 
     874             :       INTEGER                                  :: handle, i, j, k
     875             :       REAL(KIND=dp)                            :: e1, e2
     876        1384 :       REAL(KIND=dp), DIMENSION(:, :), POINTER  :: data_d
     877             :       TYPE(dbcsr_type)                          :: cmat_buf1, cmat_buf2
     878             :       TYPE(dbcsr_iterator_type)                     :: iter
     879        1384 :       COMPLEX(dp), DIMENSION(:, :), POINTER :: data_z
     880             :       INTEGER::row, col, blk, row_offset, col_offset, row_size, col_size
     881             :       LOGICAL::found
     882             :       TYPE(dbcsr_distribution_type)                       :: dist
     883             : 
     884        1384 :       CALL timeset(routineN, handle)
     885             : 
     886        1384 :       CALL dbcsr_get_info(qs_ot_env%rot_mat_u, nfullrows_total=k)
     887        1384 :       IF (k /= 0) THEN
     888        1358 :          CALL dbcsr_copy(qs_ot_env%matrix_buf1, qs_ot_env%rot_mat_dedu)
     889             :          ! now we get to the derivative wrt the antisymmetric matrix rot_mat_x
     890        1358 :          CALL dbcsr_copy(cmat_buf1, qs_ot_env%rot_mat_evec, "cmat_buf1")
     891        1358 :          CALL dbcsr_copy(cmat_buf2, qs_ot_env%rot_mat_evec, "cmat_buf2")
     892             : 
     893             :          ! init cmat_buf1
     894             :          !CALL cp_fm_get_info(qs_ot_env%matrix_buf1,matrix_struct=fm_struct, local_data=local_data_r)
     895             :          !CALL cp_cfm_get_info(cmat_buf1, nrow_local=nrow_local,   ncol_local=ncol_local, &
     896             :          !     row_indices=row_indices, col_indices=col_indices, &
     897             :          !     local_data=local_data_c)
     898             :          !local_data_c=local_data_r
     899             : 
     900        1358 :          CALL dbcsr_iterator_start(iter, cmat_buf1)
     901        2037 :          DO WHILE (dbcsr_iterator_blocks_left(iter))
     902         679 :             CALL dbcsr_iterator_next_block(iter, row, col, data_z, blk)
     903         679 :             CALL dbcsr_get_block_p(qs_ot_env%matrix_buf1, row, col, data_d, found)
     904       21459 :             data_z = data_d
     905             :          END DO
     906        1358 :          CALL dbcsr_iterator_stop(iter)
     907             : 
     908             :          CALL dbcsr_multiply('T', 'N', cone, cmat_buf1, qs_ot_env%rot_mat_evec, &
     909        1358 :                              czero, cmat_buf2)
     910             :          CALL dbcsr_multiply('C', 'N', cone, qs_ot_env%rot_mat_evec, cmat_buf2, &
     911        1358 :                              czero, cmat_buf1)
     912             : 
     913        1358 :          CALL dbcsr_iterator_start(iter, cmat_buf1)
     914        2037 :          DO WHILE (dbcsr_iterator_blocks_left(iter))
     915             :             CALL dbcsr_iterator_next_block(iter, row, col, data_z, blk, &
     916             :                                            row_size=row_size, col_size=col_size, &
     917         679 :                                            row_offset=row_offset, col_offset=col_offset)
     918        4965 :             DO j = 1, col_size
     919       20101 :             DO i = 1, row_size
     920       16494 :                e1 = qs_ot_env%rot_mat_evals(row_offset + i - 1)
     921       16494 :                e2 = qs_ot_env%rot_mat_evals(col_offset + j - 1)
     922       19422 :                data_z(i, j) = data_z(i, j)*cint(e1, e2)
     923             :             END DO
     924             :             END DO
     925             :          END DO
     926        1358 :          CALL dbcsr_iterator_stop(iter)
     927             : 
     928             :          CALL dbcsr_multiply('N', 'N', cone, qs_ot_env%rot_mat_evec, cmat_buf1, &
     929        1358 :                              czero, cmat_buf2)
     930             :          CALL dbcsr_multiply('N', 'C', cone, cmat_buf2, qs_ot_env%rot_mat_evec, &
     931        1358 :                              czero, cmat_buf1)
     932             : 
     933        1358 :          CALL dbcsr_copy(qs_ot_env%matrix_buf1, cmat_buf1)
     934             : 
     935        1358 :          CALL dbcsr_get_info(qs_ot_env%matrix_buf3, distribution=dist)
     936             :          CALL dbcsr_transposed(qs_ot_env%matrix_buf2, qs_ot_env%matrix_buf1, &
     937             :                                shallow_data_copy=.FALSE., use_distribution=dist, &
     938        1358 :                                transpose_distribution=.FALSE.)
     939             :          CALL dbcsr_add(qs_ot_env%matrix_buf1, qs_ot_env%matrix_buf2, &
     940        1358 :                         alpha_scalar=-1.0_dp, beta_scalar=+1.0_dp)
     941        1358 :          CALL dbcsr_copy(qs_ot_env%rot_mat_gx, qs_ot_env%matrix_buf1)
     942        1358 :          CALL dbcsr_release(cmat_buf1)
     943        1358 :          CALL dbcsr_release(cmat_buf2)
     944             :       END IF
     945        2768 :       CALL timestop(handle)
     946             :    CONTAINS
     947             : ! **************************************************************************************************
     948             : !> \brief ...
     949             : !> \param e1 ...
     950             : !> \param e2 ...
     951             : !> \return ...
     952             : ! **************************************************************************************************
     953       16494 :       FUNCTION cint(e1, e2)
     954             :       REAL(KIND=dp)                                      :: e1, e2
     955             :       COMPLEX(KIND=dp)                                   :: cint
     956             : 
     957             :       COMPLEX(KIND=dp)                                   :: l1, l2, x
     958             :       INTEGER                                            :: I
     959             : 
     960       16494 :          l1 = (0.0_dp, -1.0_dp)*e1
     961       16494 :          l2 = (0.0_dp, -1.0_dp)*e2
     962       16494 :          IF (ABS(l1 - l2) .GT. 0.5_dp) THEN
     963         886 :             cint = (EXP(l1) - EXP(l2))/(l1 - l2)
     964             :          ELSE
     965             :             x = 1.0_dp
     966             :             cint = 0.0_dp
     967      265336 :             DO I = 1, 16
     968      249728 :                cint = cint + x
     969      265336 :                x = x*(l1 - l2)/REAL(I + 1, KIND=dp)
     970             :             END DO
     971       15608 :             cint = cint*EXP(l2)
     972             :          END IF
     973       16494 :       END FUNCTION cint
     974             :    END SUBROUTINE qs_ot_rot_mat_derivative
     975             : 
     976             :    !
     977             :    ! decide strategy
     978             :    ! tries to decide if the taylor expansion of cos(sqrt(xsx)) converges rapidly enough
     979             :    ! to make a taylor expansion of the functions cos(sqrt(xsx)) and sin(sqrt(xsx))/sqrt(xsx)
     980             :    ! and their derivatives faster than their computation based on diagonalization
     981             :    ! since xsx can be very small, especially during dynamics, only a few terms might indeed be needed
     982             :    ! we find the necessary order N to have largest_eval_upper_bound**(N+1)/(2(N+1))! < eps_taylor
     983             :    !
     984             : ! **************************************************************************************************
     985             : !> \brief ...
     986             : !> \param qs_ot_env ...
     987             : ! **************************************************************************************************
     988       89715 :    SUBROUTINE decide_strategy(qs_ot_env)
     989             :       TYPE(qs_ot_type)                                   :: qs_ot_env
     990             : 
     991             :       INTEGER                                            :: N
     992             :       REAL(KIND=dp)                                      :: num_error
     993             : 
     994       89715 :       qs_ot_env%do_taylor = .FALSE.
     995       89715 :       N = 0
     996       89715 :       num_error = qs_ot_env%largest_eval_upper_bound/(2.0_dp)
     997      379181 :       DO WHILE (num_error > qs_ot_env%settings%eps_taylor .AND. N <= qs_ot_env%settings%max_taylor)
     998      289466 :          N = N + 1
     999      324529 :          num_error = num_error*qs_ot_env%largest_eval_upper_bound/REAL((2*N + 1)*(2*N + 2), KIND=dp)
    1000             :       END DO
    1001       89715 :       qs_ot_env%taylor_order = N
    1002       89715 :       IF (qs_ot_env%taylor_order <= qs_ot_env%settings%max_taylor) THEN
    1003       49992 :          qs_ot_env%do_taylor = .TRUE.
    1004             :       END IF
    1005             : 
    1006       89715 :    END SUBROUTINE decide_strategy
    1007             : 
    1008             :    ! c=(c0*cos(p^0.5)+x*sin(p^0.5)*p^(-0.5)) x rot_mat_u
    1009             :    ! this assumes that x is already ortho to S*C0, and that p is x*S*x
    1010             :    ! rot_mat_u is an optional rotation matrix
    1011             : ! **************************************************************************************************
    1012             : !> \brief ...
    1013             : !> \param matrix_c ...
    1014             : !> \param matrix_x ...
    1015             : !> \param qs_ot_env ...
    1016             : ! **************************************************************************************************
    1017      165908 :    SUBROUTINE qs_ot_get_orbitals(matrix_c, matrix_x, qs_ot_env)
    1018             : 
    1019             :       TYPE(dbcsr_type), POINTER                          :: matrix_c, matrix_x
    1020             :       TYPE(qs_ot_type)                                   :: qs_ot_env
    1021             : 
    1022             :       CHARACTER(len=*), PARAMETER :: routineN = 'qs_ot_get_orbitals'
    1023             :       REAL(KIND=dp), PARAMETER                           :: rone = 1.0_dp, rzero = 0.0_dp
    1024             : 
    1025             :       INTEGER                                            :: handle, k, n
    1026             :       TYPE(dbcsr_type), POINTER                          :: matrix_kk
    1027             : 
    1028       82954 :       CALL timeset(routineN, handle)
    1029             : 
    1030       82954 :       CALL dbcsr_get_info(matrix_x, nfullrows_total=n, nfullcols_total=k)
    1031             : 
    1032             :       ! rotate the multiplying matrices cosp and sinp instead of the result,
    1033             :       ! this should be cheaper for large basis sets
    1034       82954 :       IF (qs_ot_env%settings%do_rotation) THEN
    1035        2368 :          matrix_kk => qs_ot_env%matrix_buf1
    1036             :          CALL dbcsr_multiply('N', 'N', rone, qs_ot_env%matrix_cosp, &
    1037        2368 :                              qs_ot_env%rot_mat_u, rzero, matrix_kk)
    1038             :       ELSE
    1039       80586 :          matrix_kk => qs_ot_env%matrix_cosp
    1040             :       END IF
    1041             : 
    1042             :       CALL dbcsr_multiply('N', 'N', rone, qs_ot_env%matrix_c0, matrix_kk, &
    1043       82954 :                           rzero, matrix_c)
    1044             : 
    1045       82954 :       IF (qs_ot_env%settings%do_rotation) THEN
    1046        2368 :          matrix_kk => qs_ot_env%matrix_buf1
    1047             :          CALL dbcsr_multiply('N', 'N', rone, qs_ot_env%matrix_sinp, &
    1048        2368 :                              qs_ot_env%rot_mat_u, rzero, matrix_kk)
    1049             :       ELSE
    1050       80586 :          matrix_kk => qs_ot_env%matrix_sinp
    1051             :       END IF
    1052             :       CALL dbcsr_multiply('N', 'N', rone, matrix_x, matrix_kk, &
    1053       82954 :                           rone, matrix_c)
    1054             : 
    1055       82954 :       CALL timestop(handle)
    1056             : 
    1057       82954 :    END SUBROUTINE qs_ot_get_orbitals
    1058             : 
    1059             : ! **************************************************************************************************
    1060             :    ! this routines computes dE/dx=dx, with dx ortho to sc0
    1061             :    ! needs dE/dC=hc,C0,X,SX,p
    1062             :    ! if preconditioned it will not be the derivative, but the lagrangian multiplier
    1063             :    ! is changed so that P*dE/dx is the right derivative (i.e. in the allowed subspace)
    1064             : ! **************************************************************************************************
    1065             : !> \brief ...
    1066             : !> \param matrix_hc ...
    1067             : !> \param matrix_x ...
    1068             : !> \param matrix_sx ...
    1069             : !> \param matrix_gx ...
    1070             : !> \param qs_ot_env ...
    1071             : ! **************************************************************************************************
    1072      190092 :    SUBROUTINE qs_ot_get_derivative(matrix_hc, matrix_x, matrix_sx, matrix_gx, &
    1073             :                                    qs_ot_env)
    1074             :       TYPE(dbcsr_type), POINTER                          :: matrix_hc, matrix_x, matrix_sx, matrix_gx
    1075             :       TYPE(qs_ot_type)                                   :: qs_ot_env
    1076             : 
    1077             :       CHARACTER(len=*), PARAMETER :: routineN = 'qs_ot_get_derivative'
    1078             :       REAL(KIND=dp), PARAMETER                           :: rone = 1.0_dp, rzero = 0.0_dp
    1079             : 
    1080             :       INTEGER                                            :: handle, k, n, ortho_k
    1081             :       TYPE(dbcsr_type), POINTER                          :: matrix_hc_local, matrix_target
    1082             : 
    1083       63364 :       CALL timeset(routineN, handle)
    1084             : 
    1085       63364 :       NULLIFY (matrix_hc_local)
    1086             : 
    1087       63364 :       CALL dbcsr_get_info(matrix_x, nfullrows_total=n, nfullcols_total=k)
    1088             : 
    1089             :       ! could in principle be taken inside qs_ot_get_derivative_* for increased efficiency
    1090             :       ! create a local rotated version of matrix_hc leaving matrix_hc untouched (needed
    1091             :       ! for lagrangian multipliers)
    1092       63364 :       IF (qs_ot_env%settings%do_rotation) THEN
    1093        1384 :          CALL dbcsr_copy(matrix_gx, matrix_hc) ! use gx as temporary
    1094        1384 :          CALL dbcsr_init_p(matrix_hc_local)
    1095        1384 :          CALL dbcsr_copy(matrix_hc_local, matrix_hc, name='matrix_hc_local')
    1096        1384 :          CALL dbcsr_set(matrix_hc_local, 0.0_dp)
    1097        1384 :          CALL dbcsr_multiply('N', 'T', rone, matrix_gx, qs_ot_env%rot_mat_u, rzero, matrix_hc_local)
    1098             :       ELSE
    1099       61980 :          matrix_hc_local => matrix_hc
    1100             :       END IF
    1101             : 
    1102       63364 :       IF (qs_ot_env%do_taylor) THEN
    1103       36240 :          CALL qs_ot_get_derivative_taylor(matrix_hc_local, matrix_x, matrix_sx, matrix_gx, qs_ot_env)
    1104             :       ELSE
    1105       27124 :          CALL qs_ot_get_derivative_diag(matrix_hc_local, matrix_x, matrix_sx, matrix_gx, qs_ot_env)
    1106             :       END IF
    1107             : 
    1108             :       ! and make it orthogonal
    1109       63364 :       CALL dbcsr_get_info(qs_ot_env%matrix_sc0, nfullcols_total=ortho_k)
    1110             : 
    1111       63364 :       IF (ASSOCIATED(qs_ot_env%preconditioner)) THEN
    1112       51890 :          matrix_target => qs_ot_env%matrix_psc0
    1113             :       ELSE
    1114       11474 :          matrix_target => qs_ot_env%matrix_sc0
    1115             :       END IF
    1116             :       ! first make the matrix os if not yet valid
    1117       63364 :       IF (.NOT. qs_ot_env%os_valid) THEN
    1118             :          ! this assumes that the preconditioner is a single matrix
    1119             :          ! that maps sc0 onto psc0
    1120             : 
    1121        7411 :          IF (ASSOCIATED(qs_ot_env%preconditioner)) THEN
    1122             :             CALL apply_preconditioner(qs_ot_env%preconditioner, qs_ot_env%matrix_sc0, &
    1123        6313 :                                       qs_ot_env%matrix_psc0)
    1124             :          END IF
    1125             :          CALL dbcsr_multiply('T', 'N', rone, &
    1126             :                              qs_ot_env%matrix_sc0, matrix_target, &
    1127        7411 :                              rzero, qs_ot_env%matrix_os)
    1128             :          CALL cp_dbcsr_cholesky_decompose(qs_ot_env%matrix_os, &
    1129        7411 :                                           para_env=qs_ot_env%para_env, blacs_env=qs_ot_env%blacs_env)
    1130             :          CALL cp_dbcsr_cholesky_invert(qs_ot_env%matrix_os, &
    1131             :                                        para_env=qs_ot_env%para_env, blacs_env=qs_ot_env%blacs_env, &
    1132        7411 :                                        upper_to_full=.TRUE.)
    1133        7411 :          qs_ot_env%os_valid = .TRUE.
    1134             :       END IF
    1135             :       CALL dbcsr_multiply('T', 'N', rone, matrix_target, matrix_gx, &
    1136       63364 :                           rzero, qs_ot_env%matrix_buf1_ortho)
    1137             :       CALL dbcsr_multiply('N', 'N', rone, qs_ot_env%matrix_os, &
    1138       63364 :                           qs_ot_env%matrix_buf1_ortho, rzero, qs_ot_env%matrix_buf2_ortho)
    1139             :       CALL dbcsr_multiply('N', 'N', -rone, qs_ot_env%matrix_sc0, &
    1140       63364 :                           qs_ot_env%matrix_buf2_ortho, rone, matrix_gx)
    1141             :       ! also treat the rot_mat gradient here
    1142       63364 :       IF (qs_ot_env%settings%do_rotation) THEN
    1143        1384 :          CALL qs_ot_rot_mat_derivative(qs_ot_env)
    1144             :       END IF
    1145             : 
    1146       63364 :       IF (qs_ot_env%settings%do_rotation) THEN
    1147        1384 :          CALL dbcsr_release_p(matrix_hc_local)
    1148             :       END IF
    1149             : 
    1150       63364 :       CALL timestop(handle)
    1151             : 
    1152       63364 :    END SUBROUTINE qs_ot_get_derivative
    1153             : 
    1154             : ! **************************************************************************************************
    1155             : !> \brief ...
    1156             : !> \param matrix_hc ...
    1157             : !> \param matrix_x ...
    1158             : !> \param matrix_sx ...
    1159             : !> \param matrix_gx ...
    1160             : !> \param qs_ot_env ...
    1161             : ! **************************************************************************************************
    1162       81372 :    SUBROUTINE qs_ot_get_derivative_diag(matrix_hc, matrix_x, matrix_sx, matrix_gx, &
    1163             :                                         qs_ot_env)
    1164             : 
    1165             :       TYPE(dbcsr_type), POINTER                          :: matrix_hc, matrix_x, matrix_sx, matrix_gx
    1166             :       TYPE(qs_ot_type)                                   :: qs_ot_env
    1167             : 
    1168             :       CHARACTER(len=*), PARAMETER :: routineN = 'qs_ot_get_derivative_diag'
    1169             :       REAL(KIND=dp), PARAMETER                           :: rone = 1.0_dp, rzero = 0.0_dp
    1170             : 
    1171             :       INTEGER                                            :: handle, k, n
    1172             :       TYPE(dbcsr_distribution_type)                      :: dist
    1173             : 
    1174       27124 :       CALL timeset(routineN, handle)
    1175             : 
    1176       27124 :       CALL dbcsr_get_info(matrix_x, nfullrows_total=n, nfullcols_total=k)
    1177             : 
    1178             :       ! go for the derivative now
    1179             :       ! this de/dc*(dX/dx)*sinp
    1180       27124 :       CALL dbcsr_multiply('N', 'N', rone, matrix_hc, qs_ot_env%matrix_sinp, rzero, matrix_gx)
    1181             :       ! overlap hc*x
    1182       27124 :       CALL dbcsr_multiply('T', 'N', rone, matrix_hc, matrix_x, rzero, qs_ot_env%matrix_buf2)
    1183             :       ! get it in the basis of the eigenvectors
    1184             :       CALL dbcsr_multiply('N', 'N', rone, qs_ot_env%matrix_buf2, qs_ot_env%matrix_r, &
    1185       27124 :                           rzero, qs_ot_env%matrix_buf1)
    1186             :       CALL dbcsr_multiply('T', 'N', rone, qs_ot_env%matrix_r, qs_ot_env%matrix_buf1, &
    1187       27124 :                           rzero, qs_ot_env%matrix_buf2)
    1188             : 
    1189             :       ! get the schur product of O_uv*B_uv
    1190             :       CALL dbcsr_hadamard_product(qs_ot_env%matrix_buf2, qs_ot_env%matrix_sinp_b, &
    1191       27124 :                                   qs_ot_env%matrix_buf3)
    1192             : 
    1193             :       ! overlap hc*c0
    1194             :       CALL dbcsr_multiply('T', 'N', rone, matrix_hc, qs_ot_env%matrix_c0, rzero, &
    1195       27124 :                           qs_ot_env%matrix_buf2)
    1196             :       ! get it in the basis of the eigenvectors
    1197             :       CALL dbcsr_multiply('N', 'N', rone, qs_ot_env%matrix_buf2, qs_ot_env%matrix_r, &
    1198       27124 :                           rzero, qs_ot_env%matrix_buf1)
    1199             :       CALL dbcsr_multiply('T', 'N', rone, qs_ot_env%matrix_r, qs_ot_env%matrix_buf1, &
    1200       27124 :                           rzero, qs_ot_env%matrix_buf2)
    1201             : 
    1202             :       CALL dbcsr_hadamard_product(qs_ot_env%matrix_buf2, qs_ot_env%matrix_cosp_b, &
    1203       27124 :                                   qs_ot_env%matrix_buf4)
    1204             : 
    1205             :       ! add the two bs and compute b+b^T
    1206             :       CALL dbcsr_add(qs_ot_env%matrix_buf3, qs_ot_env%matrix_buf4, &
    1207       27124 :                      alpha_scalar=rone, beta_scalar=rone)
    1208             : 
    1209             :       ! get the b in the eigenvector basis
    1210             :       CALL dbcsr_multiply('N', 'T', rone, qs_ot_env%matrix_buf3, qs_ot_env%matrix_r, &
    1211       27124 :                           rzero, qs_ot_env%matrix_buf1)
    1212             :       CALL dbcsr_multiply('N', 'N', rone, qs_ot_env%matrix_r, qs_ot_env%matrix_buf1, &
    1213       27124 :                           rzero, qs_ot_env%matrix_buf3)
    1214       27124 :       CALL dbcsr_get_info(qs_ot_env%matrix_buf3, distribution=dist)
    1215             :       CALL dbcsr_transposed(qs_ot_env%matrix_buf1, qs_ot_env%matrix_buf3, &
    1216             :                             shallow_data_copy=.FALSE., use_distribution=dist, &
    1217       27124 :                             transpose_distribution=.FALSE.)
    1218             :       CALL dbcsr_add(qs_ot_env%matrix_buf3, qs_ot_env%matrix_buf1, &
    1219       27124 :                      alpha_scalar=rone, beta_scalar=rone)
    1220             : 
    1221             :       ! and add to the derivative
    1222             :       CALL dbcsr_multiply('N', 'N', rone, matrix_sx, qs_ot_env%matrix_buf3, &
    1223       27124 :                           rone, matrix_gx)
    1224       27124 :       CALL timestop(handle)
    1225             : 
    1226       27124 :    END SUBROUTINE qs_ot_get_derivative_diag
    1227             : 
    1228             :    ! compute the derivative of the taylor expansion below
    1229             : ! **************************************************************************************************
    1230             : !> \brief ...
    1231             : !> \param matrix_hc ...
    1232             : !> \param matrix_x ...
    1233             : !> \param matrix_sx ...
    1234             : !> \param matrix_gx ...
    1235             : !> \param qs_ot_env ...
    1236             : ! **************************************************************************************************
    1237      129674 :    SUBROUTINE qs_ot_get_derivative_taylor(matrix_hc, matrix_x, matrix_sx, matrix_gx, &
    1238             :                                           qs_ot_env)
    1239             : 
    1240             :       TYPE(dbcsr_type), POINTER                          :: matrix_hc, matrix_x, matrix_sx, matrix_gx
    1241             :       TYPE(qs_ot_type)                                   :: qs_ot_env
    1242             : 
    1243             :       CHARACTER(len=*), PARAMETER :: routineN = 'qs_ot_get_derivative_taylor'
    1244             :       REAL(KIND=dp), PARAMETER                           :: rone = 1.0_dp, rzero = 0.0_dp
    1245             : 
    1246             :       INTEGER                                            :: handle, i, k, n
    1247             :       REAL(KIND=dp)                                      :: cosfactor, sinfactor
    1248             :       TYPE(dbcsr_distribution_type)                      :: dist
    1249             :       TYPE(dbcsr_type), POINTER                          :: matrix_left, matrix_right
    1250             : 
    1251       36240 :       CALL timeset(routineN, handle)
    1252             : 
    1253       36240 :       CALL dbcsr_get_info(matrix_x, nfullrows_total=n, nfullcols_total=k)
    1254             : 
    1255             :       ! go for the derivative now
    1256             :       ! this de/dc*(dX/dx)*sinp i.e. zeroth order
    1257       36240 :       CALL dbcsr_multiply('N', 'N', rone, matrix_hc, qs_ot_env%matrix_sinp, rzero, matrix_gx)
    1258             : 
    1259       36240 :       IF (qs_ot_env%taylor_order .LE. 0) THEN
    1260        7643 :          CALL timestop(handle)
    1261        7643 :          RETURN
    1262             :       END IF
    1263             : 
    1264             :       ! we store the matrix that will multiply sx in matrix_r
    1265       28597 :       CALL dbcsr_set(qs_ot_env%matrix_r, rzero)
    1266             : 
    1267             :       ! just better names for matrix_cosp_b and matrix_sinp_b (they are buffer space here)
    1268       28597 :       matrix_left => qs_ot_env%matrix_cosp_b
    1269       28597 :       matrix_right => qs_ot_env%matrix_sinp_b
    1270             : 
    1271             :       ! overlap hc*x and add its transpose to matrix_left
    1272       28597 :       CALL dbcsr_multiply('T', 'N', rone, matrix_hc, matrix_x, rzero, matrix_left)
    1273       28597 :       CALL dbcsr_get_info(matrix_left, distribution=dist)
    1274             :       CALL dbcsr_transposed(qs_ot_env%matrix_buf1, matrix_left, &
    1275             :                             shallow_data_copy=.FALSE., use_distribution=dist, &
    1276       28597 :                             transpose_distribution=.FALSE.)
    1277             :       CALL dbcsr_add(matrix_left, qs_ot_env%matrix_buf1, &
    1278       28597 :                      alpha_scalar=1.0_dp, beta_scalar=1.0_dp)
    1279       28597 :       CALL dbcsr_copy(matrix_right, matrix_left)
    1280             : 
    1281             :       ! first order
    1282       28597 :       sinfactor = -1.0_dp/(2.0_dp*3.0_dp)
    1283             :       CALL dbcsr_add(qs_ot_env%matrix_r, matrix_left, &
    1284       28597 :                      alpha_scalar=1.0_dp, beta_scalar=sinfactor)
    1285             : 
    1286             :       !      M
    1287             :       !    OM+MO
    1288             :       ! OOM+OMO+MOO
    1289             :       !   ...
    1290       61435 :       DO i = 2, qs_ot_env%taylor_order
    1291       32838 :          sinfactor = sinfactor*(-1.0_dp)/REAL(2*i*(2*i + 1), KIND=dp)
    1292       32838 :          CALL dbcsr_multiply('N', 'N', rone, qs_ot_env%matrix_p, matrix_left, rzero, qs_ot_env%matrix_buf1)
    1293       32838 :          CALL dbcsr_multiply('N', 'N', rone, matrix_right, qs_ot_env%matrix_p, rzero, matrix_left)
    1294       32838 :          CALL dbcsr_copy(matrix_right, matrix_left)
    1295             :          CALL dbcsr_add(matrix_left, qs_ot_env%matrix_buf1, &
    1296       32838 :                         1.0_dp, 1.0_dp)
    1297             :          CALL dbcsr_add(qs_ot_env%matrix_r, matrix_left, &
    1298       61435 :                         alpha_scalar=1.0_dp, beta_scalar=sinfactor)
    1299             :       END DO
    1300             : 
    1301             :       ! overlap hc*c0 and add its transpose to matrix_left
    1302       28597 :       CALL dbcsr_multiply('T', 'N', rone, matrix_hc, qs_ot_env%matrix_c0, rzero, matrix_left)
    1303       28597 :       CALL dbcsr_get_info(matrix_left, distribution=dist)
    1304             :       CALL dbcsr_transposed(qs_ot_env%matrix_buf1, matrix_left, &
    1305             :                             shallow_data_copy=.FALSE., use_distribution=dist, &
    1306       28597 :                             transpose_distribution=.FALSE.)
    1307       28597 :       CALL dbcsr_add(matrix_left, qs_ot_env%matrix_buf1, 1.0_dp, 1.0_dp)
    1308       28597 :       CALL dbcsr_copy(matrix_right, matrix_left)
    1309             : 
    1310             :       ! first order
    1311       28597 :       cosfactor = -1.0_dp/(1.0_dp*2.0_dp)
    1312             :       CALL dbcsr_add(qs_ot_env%matrix_r, matrix_left, &
    1313       28597 :                      alpha_scalar=1.0_dp, beta_scalar=cosfactor)
    1314             : 
    1315             :       !      M
    1316             :       !    OM+MO
    1317             :       ! OOM+OMO+MOO
    1318             :       !   ...
    1319       61435 :       DO i = 2, qs_ot_env%taylor_order
    1320       32838 :          cosfactor = cosfactor*(-1.0_dp)/REAL(2*i*(2*i - 1), KIND=dp)
    1321       32838 :          CALL dbcsr_multiply('N', 'N', rone, qs_ot_env%matrix_p, matrix_left, rzero, qs_ot_env%matrix_buf1)
    1322       32838 :          CALL dbcsr_multiply('N', 'N', rone, matrix_right, qs_ot_env%matrix_p, rzero, matrix_left)
    1323       32838 :          CALL dbcsr_copy(matrix_right, matrix_left)
    1324       32838 :          CALL dbcsr_add(matrix_left, qs_ot_env%matrix_buf1, 1.0_dp, 1.0_dp)
    1325             :          CALL dbcsr_add(qs_ot_env%matrix_r, matrix_left, &
    1326       61435 :                         alpha_scalar=1.0_dp, beta_scalar=cosfactor)
    1327             :       END DO
    1328             : 
    1329             :       ! and add to the derivative
    1330       28597 :       CALL dbcsr_multiply('N', 'N', rone, matrix_sx, qs_ot_env%matrix_r, rone, matrix_gx)
    1331             : 
    1332       28597 :       CALL timestop(handle)
    1333             : 
    1334       36240 :    END SUBROUTINE qs_ot_get_derivative_taylor
    1335             : 
    1336             :    ! computes a taylor expansion.
    1337             : ! **************************************************************************************************
    1338             : !> \brief ...
    1339             : !> \param qs_ot_env ...
    1340             : ! **************************************************************************************************
    1341       81974 :    SUBROUTINE qs_ot_p2m_taylor(qs_ot_env)
    1342             :       TYPE(qs_ot_type)                                   :: qs_ot_env
    1343             : 
    1344             :       CHARACTER(len=*), PARAMETER                        :: routineN = 'qs_ot_p2m_taylor'
    1345             :       REAL(KIND=dp), PARAMETER                           :: rone = 1.0_dp, rzero = 0.0_dp
    1346             : 
    1347             :       INTEGER                                            :: handle, i, k
    1348             :       REAL(KIND=dp)                                      :: cosfactor, sinfactor
    1349             : 
    1350       49992 :       CALL timeset(routineN, handle)
    1351             : 
    1352             :       ! zeroth order
    1353       49992 :       CALL dbcsr_set(qs_ot_env%matrix_cosp, rzero)
    1354       49992 :       CALL dbcsr_set(qs_ot_env%matrix_sinp, rzero)
    1355       49992 :       CALL dbcsr_add_on_diag(qs_ot_env%matrix_cosp, rone)
    1356       49992 :       CALL dbcsr_add_on_diag(qs_ot_env%matrix_sinp, rone)
    1357             : 
    1358       49992 :       IF (qs_ot_env%taylor_order .LE. 0) THEN
    1359        8221 :          CALL timestop(handle)
    1360       18010 :          RETURN
    1361             :       END IF
    1362             : 
    1363             :       ! first order
    1364       41771 :       cosfactor = -1.0_dp/(1.0_dp*2.0_dp)
    1365       41771 :       sinfactor = -1.0_dp/(2.0_dp*3.0_dp)
    1366       41771 :       CALL dbcsr_add(qs_ot_env%matrix_cosp, qs_ot_env%matrix_p, alpha_scalar=1.0_dp, beta_scalar=cosfactor)
    1367       41771 :       CALL dbcsr_add(qs_ot_env%matrix_sinp, qs_ot_env%matrix_p, alpha_scalar=1.0_dp, beta_scalar=sinfactor)
    1368       41771 :       IF (qs_ot_env%taylor_order .LE. 1) THEN
    1369        9789 :          CALL timestop(handle)
    1370        9789 :          RETURN
    1371             :       END IF
    1372             : 
    1373             :       ! other orders
    1374       31982 :       CALL dbcsr_get_info(qs_ot_env%matrix_p, nfullrows_total=k)
    1375       31982 :       CALL dbcsr_copy(qs_ot_env%matrix_r, qs_ot_env%matrix_p)
    1376             : 
    1377       81062 :       DO i = 2, qs_ot_env%taylor_order
    1378             :          ! new power of p
    1379             :          CALL dbcsr_multiply('N', 'N', rone, qs_ot_env%matrix_p, qs_ot_env%matrix_r, &
    1380       49080 :                              rzero, qs_ot_env%matrix_buf1)
    1381       49080 :          CALL dbcsr_copy(qs_ot_env%matrix_r, qs_ot_env%matrix_buf1)
    1382             :          ! add to the taylor expansion so far
    1383       49080 :          cosfactor = cosfactor*(-1.0_dp)/REAL(2*i*(2*i - 1), KIND=dp)
    1384       49080 :          sinfactor = sinfactor*(-1.0_dp)/REAL(2*i*(2*i + 1), KIND=dp)
    1385             :          CALL dbcsr_add(qs_ot_env%matrix_cosp, qs_ot_env%matrix_r, &
    1386       49080 :                         alpha_scalar=1.0_dp, beta_scalar=cosfactor)
    1387             :          CALL dbcsr_add(qs_ot_env%matrix_sinp, qs_ot_env%matrix_r, &
    1388       81062 :                         alpha_scalar=1.0_dp, beta_scalar=sinfactor)
    1389             :       END DO
    1390             : 
    1391       31982 :       CALL timestop(handle)
    1392             : 
    1393             :    END SUBROUTINE qs_ot_p2m_taylor
    1394             : 
    1395             :    ! given p, computes  - eigenstuff (matrix_r,evals)
    1396             :    !                    - cos(p^0.5),p^(-0.5)*sin(p^0.5)
    1397             :    !                    - the real b matrices, needed for the derivatives of these guys
    1398             :    !                    cosp_b_ij=(1/(2pii) * int(cos(z^1/2)/((z-eval(i))*(z-eval(j))))
    1399             :    !                    sinp_b_ij=(1/(2pii) * int(z^(-1/2)*sin(z^1/2)/((z-eval(i))*(z-eval(j))))
    1400             : ! **************************************************************************************************
    1401             : !> \brief ...
    1402             : !> \param qs_ot_env ...
    1403             : ! **************************************************************************************************
    1404      158892 :    SUBROUTINE qs_ot_p2m_diag(qs_ot_env)
    1405             : 
    1406             :       TYPE(qs_ot_type)                                   :: qs_ot_env
    1407             : 
    1408             :       CHARACTER(len=*), PARAMETER                        :: routineN = 'qs_ot_p2m_diag'
    1409             :       REAL(KIND=dp), PARAMETER                           :: rone = 1.0_dp, rzero = 0.0_dp
    1410             : 
    1411             :       INTEGER                                            :: blk, col, col_offset, col_size, handle, &
    1412             :                                                             i, j, k, row, row_offset, row_size
    1413       39723 :       REAL(dp), DIMENSION(:, :), POINTER                 :: DATA
    1414             :       REAL(KIND=dp)                                      :: a, b
    1415             :       TYPE(dbcsr_iterator_type)                          :: iter
    1416             : 
    1417       39723 :       CALL timeset(routineN, handle)
    1418             : 
    1419       39723 :       CALL dbcsr_get_info(qs_ot_env%matrix_p, nfullrows_total=k)
    1420       39723 :       CALL dbcsr_copy(qs_ot_env%matrix_buf1, qs_ot_env%matrix_p)
    1421             :       CALL cp_dbcsr_syevd(qs_ot_env%matrix_buf1, qs_ot_env%matrix_r, qs_ot_env%evals, &
    1422       39723 :                           qs_ot_env%para_env, qs_ot_env%blacs_env)
    1423      442601 :       DO i = 1, k
    1424      442601 :          qs_ot_env%evals(i) = MAX(0.0_dp, qs_ot_env%evals(i))
    1425             :       END DO
    1426             : 
    1427       39723 : !$OMP     PARALLEL DO DEFAULT(NONE) PRIVATE(i) SHARED(k,qs_ot_env)
    1428             :       DO i = 1, k
    1429             :          qs_ot_env%dum(i) = COS(SQRT(qs_ot_env%evals(i)))
    1430             :       END DO
    1431       39723 :       CALL dbcsr_copy(qs_ot_env%matrix_buf1, qs_ot_env%matrix_r)
    1432       39723 :       CALL dbcsr_scale_by_vector(qs_ot_env%matrix_buf1, alpha=qs_ot_env%dum, side='right')
    1433             :       CALL dbcsr_multiply('N', 'T', rone, qs_ot_env%matrix_r, qs_ot_env%matrix_buf1, &
    1434       39723 :                           rzero, qs_ot_env%matrix_cosp)
    1435             : 
    1436       39723 : !$OMP     PARALLEL DO DEFAULT(NONE) PRIVATE(i) SHARED(k,qs_ot_env)
    1437             :       DO i = 1, k
    1438             :          qs_ot_env%dum(i) = qs_ot_sinc(SQRT(qs_ot_env%evals(i)))
    1439             :       END DO
    1440       39723 :       CALL dbcsr_copy(qs_ot_env%matrix_buf1, qs_ot_env%matrix_r)
    1441       39723 :       CALL dbcsr_scale_by_vector(qs_ot_env%matrix_buf1, alpha=qs_ot_env%dum, side='right')
    1442             :       CALL dbcsr_multiply('N', 'T', rone, qs_ot_env%matrix_r, qs_ot_env%matrix_buf1, &
    1443       39723 :                           rzero, qs_ot_env%matrix_sinp)
    1444             : 
    1445       39723 :       CALL dbcsr_copy(qs_ot_env%matrix_cosp_b, qs_ot_env%matrix_cosp)
    1446       39723 :       CALL dbcsr_iterator_start(iter, qs_ot_env%matrix_cosp_b)
    1447       69684 :       DO WHILE (dbcsr_iterator_blocks_left(iter))
    1448             :          CALL dbcsr_iterator_next_block(iter, row, col, DATA, &
    1449             :                                         block_number=blk, row_size=row_size, col_size=col_size, &
    1450       29961 :                                         row_offset=row_offset, col_offset=col_offset)
    1451      478674 :          DO j = 1, col_size
    1452     9633716 :          DO i = 1, row_size
    1453             :             a = (SQRT(qs_ot_env%evals(row_offset + i - 1)) &
    1454     9194765 :                  - SQRT(qs_ot_env%evals(col_offset + j - 1)))/2.0_dp
    1455             :             b = (SQRT(qs_ot_env%evals(row_offset + i - 1)) &
    1456     9194765 :                  + SQRT(qs_ot_env%evals(col_offset + j - 1)))/2.0_dp
    1457     9603755 :             DATA(i, j) = -0.5_dp*qs_ot_sinc(a)*qs_ot_sinc(b)
    1458             :          END DO
    1459             :          END DO
    1460             :       END DO
    1461       39723 :       CALL dbcsr_iterator_stop(iter)
    1462             : 
    1463       39723 :       CALL dbcsr_copy(qs_ot_env%matrix_sinp_b, qs_ot_env%matrix_sinp)
    1464       39723 :       CALL dbcsr_iterator_start(iter, qs_ot_env%matrix_sinp_b)
    1465       69684 :       DO WHILE (dbcsr_iterator_blocks_left(iter))
    1466             :          CALL dbcsr_iterator_next_block(iter, row, col, DATA, &
    1467             :                                         block_number=blk, row_size=row_size, col_size=col_size, &
    1468       29961 :                                         row_offset=row_offset, col_offset=col_offset)
    1469      478674 :          DO j = 1, col_size
    1470     9633716 :          DO i = 1, row_size
    1471     9194765 :             a = SQRT(qs_ot_env%evals(row_offset + i - 1))
    1472     9194765 :             b = SQRT(qs_ot_env%evals(col_offset + j - 1))
    1473     9603755 :             DATA(i, j) = qs_ot_sincf(a, b)
    1474             :          END DO
    1475             :          END DO
    1476             :       END DO
    1477       39723 :       CALL dbcsr_iterator_stop(iter)
    1478             : 
    1479       39723 :       CALL timestop(handle)
    1480             : 
    1481       39723 :    END SUBROUTINE qs_ot_p2m_diag
    1482             : 
    1483             :    ! computes sin(x)/x for all values of the argument
    1484             : ! **************************************************************************************************
    1485             : !> \brief ...
    1486             : !> \param x ...
    1487             : !> \return ...
    1488             : ! **************************************************************************************************
    1489    25238106 :    FUNCTION qs_ot_sinc(x)
    1490             : 
    1491             :       REAL(KIND=dp), INTENT(IN)                          :: x
    1492             :       REAL(KIND=dp)                                      :: qs_ot_sinc
    1493             : 
    1494             :       REAL(KIND=dp), PARAMETER :: q1 = 1.0_dp, q2 = -q1/(2.0_dp*3.0_dp), q3 = -q2/(4.0_dp*5.0_dp), &
    1495             :          q4 = -q3/(6.0_dp*7.0_dp), q5 = -q4/(8.0_dp*9.0_dp), q6 = -q5/(10.0_dp*11.0_dp), &
    1496             :          q7 = -q6/(12.0_dp*13.0_dp), q8 = -q7/(14.0_dp*15.0_dp), q9 = -q8/(16.0_dp*17.0_dp), &
    1497             :          q10 = -q9/(18.0_dp*19.0_dp)
    1498             : 
    1499             :       REAL(KIND=dp)                                      :: y
    1500             : 
    1501    25238106 :       IF (ABS(x) > 0.5_dp) THEN
    1502     7251797 :          qs_ot_sinc = SIN(x)/x
    1503             :       ELSE
    1504    17986309 :          y = x*x
    1505    17986309 :          qs_ot_sinc = q1 + y*(q2 + y*(q3 + y*(q4 + y*(q5 + y*(q6 + y*(q7 + y*(q8 + y*(q9 + y*(q10)))))))))
    1506             :       END IF
    1507    25238106 :    END FUNCTION qs_ot_sinc
    1508             :    ! computes (1/(x^2-y^2))*(sinc(x)-sinc(y)) for all positive values of the arguments
    1509             : ! **************************************************************************************************
    1510             : !> \brief ...
    1511             : !> \param xa ...
    1512             : !> \param ya ...
    1513             : !> \return ...
    1514             : ! **************************************************************************************************
    1515     9194765 :    FUNCTION qs_ot_sincf(xa, ya)
    1516             : 
    1517             :       REAL(KIND=dp), INTENT(IN)                          :: xa, ya
    1518             :       REAL(KIND=dp)                                      :: qs_ot_sincf
    1519             : 
    1520             :       INTEGER                                            :: i
    1521             :       REAL(KIND=dp)                                      :: a, b, rs, sf, x, xs, y, ybx, ybxs
    1522             : 
    1523             : ! this is currently a limit of the routine, could be removed rather easily
    1524             : 
    1525     9194765 :       IF (xa .LT. 0) CPABORT("x is negative")
    1526     9194765 :       IF (ya .LT. 0) CPABORT("y is negative")
    1527             : 
    1528     9194765 :       IF (xa .LT. ya) THEN
    1529     4429293 :          x = ya
    1530     4429293 :          y = xa
    1531             :       ELSE
    1532     4765472 :          x = xa
    1533     4765472 :          y = ya
    1534             :       END IF
    1535             : 
    1536     9194765 :       IF (x .LT. 0.5_dp) THEN ! use series, keeping in mind that x,y,x+y,x-y can all be zero
    1537             : 
    1538     5971916 :          qs_ot_sincf = 0.0_dp
    1539     5971916 :          IF (x .GT. 0.0_dp) THEN
    1540     5823232 :             ybx = y/x
    1541             :          ELSE ! should be irrelevant  !?
    1542             :             ybx = 0.0_dp
    1543             :          END IF
    1544             : 
    1545     5971916 :          sf = -1.0_dp/((1.0_dp + ybx)*6.0_dp)
    1546     5971916 :          rs = 1.0_dp
    1547     5971916 :          ybxs = ybx
    1548     5971916 :          xs = 1.0_dp
    1549             : 
    1550    65691076 :          DO i = 1, 10
    1551    59719160 :             qs_ot_sincf = qs_ot_sincf + sf*rs*xs*(1.0_dp + ybxs)
    1552    59719160 :             sf = -sf/(REAL((2*i + 2), dp)*REAL((2*i + 3), dp))
    1553    59719160 :             rs = rs + ybxs
    1554    59719160 :             ybxs = ybxs*ybx
    1555    65691076 :             xs = xs*x*x
    1556             :          END DO
    1557             : 
    1558             :       ELSE ! no series expansion
    1559     3222849 :          IF (x - y .GT. 0.1_dp) THEN ! safe to use the normal form
    1560     2978542 :             qs_ot_sincf = (qs_ot_sinc(x) - qs_ot_sinc(y))/((x + y)*(x - y))
    1561             :          ELSE
    1562      244307 :             a = (x + y)/2.0_dp
    1563      244307 :             b = (x - y)/2.0_dp ! might be close to zero
    1564             :             ! y (=(a-b)) can not be close to zero since it is close to x>0.5
    1565      244307 :             qs_ot_sincf = (qs_ot_sinc(b)*COS(a) - qs_ot_sinc(a)*COS(b))/(2*x*y)
    1566             :          END IF
    1567             :       END IF
    1568             : 
    1569     9194765 :    END FUNCTION qs_ot_sincf
    1570             : 
    1571             : END MODULE qs_ot

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