!--------------------------------------------------------------------------------------------------!
!   CP2K: A general program to perform molecular dynamics simulations                              !
!   Copyright (C) 2000 - 2017  CP2K developers group                                               !
!--------------------------------------------------------------------------------------------------!

! **************************************************************************************************
!> \brief function that builds the hartree fock exchange section of the input
!> \par History
!>      09.2007 created
!> \author Manuel Guidon
! **************************************************************************************************
MODULE input_cp2k_hfx
   USE bibliography,                    ONLY: Guidon2008,&
                                              Guidon2009
   USE cp_output_handling,              ONLY: add_last_numeric,&
                                              cp_print_key_section_create,&
                                              medium_print_level
   USE input_constants,                 ONLY: &
        do_hfx_potential_coulomb, do_hfx_potential_gaussian, do_hfx_potential_id, &
        do_hfx_potential_long, do_hfx_potential_mix_cl, do_hfx_potential_mix_cl_trunc, &
        do_hfx_potential_mix_lg, do_hfx_potential_short, do_hfx_potential_truncated, ehrenfest, &
        gaussian
   USE input_keyword_types,             ONLY: keyword_create,&
                                              keyword_release,&
                                              keyword_type
   USE input_section_types,             ONLY: section_add_keyword,&
                                              section_add_subsection,&
                                              section_create,&
                                              section_release,&
                                              section_type
   USE input_val_types,                 ONLY: real_t
   USE kinds,                           ONLY: dp
   USE string_utilities,                ONLY: s2a
#include "./base/base_uses.f90"

   IMPLICIT NONE
   PRIVATE

   LOGICAL, PRIVATE, PARAMETER :: debug_this_module = .FALSE.
   CHARACTER(len=*), PARAMETER, PRIVATE :: moduleN = 'input_cp2k_hfx'

   PUBLIC :: create_hfx_section

CONTAINS

! **************************************************************************************************
!> \brief creates the input section for the hf part
!> \param section the section to create
!> \author Manuel Guidon
! **************************************************************************************************
   SUBROUTINE create_hfx_section(section)
      TYPE(section_type), POINTER                        :: section

      CHARACTER(len=*), PARAMETER :: routineN = 'create_hfx_section', &
         routineP = moduleN//':'//routineN

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: print_key, subsection

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, "HF", &
                          description="Sets up the Hartree-Fock parameters if requested ", &
                          n_keywords=5, n_subsections=2, repeats=.TRUE., &
                          citations=(/Guidon2008, Guidon2009/))

      NULLIFY (keyword, print_key, subsection)

      CALL keyword_create(keyword, name="FRACTION", &
                          description="The fraction of Hartree-Fock to add to the total energy. "// &
                          "1.0 implies standard Hartree-Fock if used with XC_FUNCTIONAL NONE. "// &
                          "NOTE: In a mixed potential calculation this should be set to 1.0, otherwise "// &
                          "all parts are multiplied with this factor. ", &
                          usage="FRACTION 1.0", default_r_val=1.0_dp)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, name="TREAT_LSD_IN_CORE", &
                          description="Determines how spin denisities are taken into account. "// &
                          "If true, the beta spin density is included via a second in core call. "// &
                          "If false, alpha and beta spins are done in one shot ", &
                          usage="TREAT_LSD_IN_CORE TRUE", default_l_val=.FALSE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, name="PW_HFX", &
                          description="Compute the Hartree-Fock energy also in the plane wave basis."// &
                          "The value is ignored, and intended for debugging only.", &
                          usage="PW_HFX FALSE", default_l_val=.FALSE., lone_keyword_l_val=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, name="PW_HFX_BLOCKSIZE", &
                          description="Improve the performance of pw_hfx at the cost of some additional memory "// &
                          "by storing the realspace representation of PW_HFX_BLOCKSIZE states.", &
                          usage="PW_HFX_BLOCKSIZE 20", default_i_val=20)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      NULLIFY (print_key)
      CALL cp_print_key_section_create(print_key, "HF_INFO", &
                                       description="Controls the printing basic info about hf method", &
                                       print_level=medium_print_level, add_last=add_last_numeric, filename="__STD_OUT__")
      CALL section_add_subsection(section, print_key)
      CALL section_release(print_key)

      CALL create_hf_pbc_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_hf_screening_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_hf_potential_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_hf_load_balance_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

      CALL create_hf_memory_section(subsection)
      CALL section_add_subsection(section, subsection)
      CALL section_release(subsection)

   END SUBROUTINE create_hfx_section

! **************************************************************************************************
!> \brief !****f* input_cp2k_dft/create_hf_load_balance_section [1.0] *
!>
!>      creates the input section for the hf potential part
!> \param section the section to create
!> \author Manuel Guidon
! **************************************************************************************************
   SUBROUTINE create_hf_load_balance_section(section)
      TYPE(section_type), POINTER                        :: section

      CHARACTER(len=*), PARAMETER :: routineN = 'create_hf_load_balance_section', &
         routineP = moduleN//':'//routineN

      TYPE(keyword_type), POINTER                        :: keyword
      TYPE(section_type), POINTER                        :: print_key

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, "LOAD_BALANCE", &
                          description="Parameters influencing the load balancing of the HF", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE., &
                          citations=(/guidon2008/))

      NULLIFY (keyword)
      CALL keyword_create( &
         keyword=keyword, &
         name="NBINS", &
         description="Number of bins per process used to group atom quartets.", &
         usage="NBINS 32", &
         default_i_val=64)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create( &
         keyword=keyword, &
         name="BLOCK_SIZE", &
         description="Determines the blocking used for the atomic quartet loops. "// &
         "A proper choice can speedup the calculation. The default (-1) is automatic.", &
         usage="BLOCK_SIZE 4", &
         default_i_val=-1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      NULLIFY (keyword)
      CALL keyword_create( &
         keyword=keyword, &
         name="RANDOMIZE", &
         description="This flag controls the randomization of the bin assignment to processes. "// &
         "For highly ordered input structures with a bad load balance, setting "// &
         "this flag to TRUE might improve.", &
         usage="RANDOMIZE TRUE", &
         default_l_val=.FALSE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      NULLIFY (print_key)
      CALL cp_print_key_section_create(print_key, "PRINT", &
                                       description="Controls the printing of info about load balance", &
                                       print_level=medium_print_level, add_last=add_last_numeric, filename="__STD_OUT__")
      CALL section_add_subsection(section, print_key)

      CALL keyword_release(keyword)
      CALL keyword_create(keyword=keyword, &
                          name="LOAD_BALANCE_INFO", &
                          description="Activates the printing of load balance information ", &
                          default_l_val=.FALSE., &
                          lone_keyword_l_val=.TRUE.)
      CALL section_add_keyword(print_key, keyword)
      CALL keyword_release(keyword)
      CALL section_release(print_key)

   END SUBROUTINE create_hf_load_balance_section

! **************************************************************************************************
!> \brief !****f* input_cp2k_dft/create_hf_potential_section [1.0] *
!>
!>      creates the input section for the hf potential part
!> \param section the section to create
!> \author Manuel Guidon
! **************************************************************************************************
   SUBROUTINE create_hf_potential_section(section)
      TYPE(section_type), POINTER                        :: section

      CHARACTER(len=*), PARAMETER :: routineN = 'create_hf_potential_section', &
         routineP = moduleN//':'//routineN

      TYPE(keyword_type), POINTER                        :: keyword

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, "INTERACTION_POTENTIAL", &
                          description="Sets up interaction potential if requested ", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE., &
                          citations=(/guidon2008, guidon2009/))

      NULLIFY (keyword)
      CALL keyword_create( &
         keyword=keyword, &
         name="POTENTIAL_TYPE", &
         description="Which interaction potential should be used "// &
         "(Coulomb, longrange or shortrange).", &
         usage="POTENTIAL_TYPE SHORTRANGE", &
         enum_c_vals=s2a("COULOMB", "SHORTRANGE", "LONGRANGE", "MIX_CL", "GAUSSIAN", &
                         "MIX_LG", "IDENTITY", "TRUNCATED", "MIX_CL_TRUNC"), &
         enum_i_vals=(/do_hfx_potential_coulomb, do_hfx_potential_short, do_hfx_potential_long, &
                       do_hfx_potential_mix_cl, do_hfx_potential_gaussian, do_hfx_potential_mix_lg, &
                       do_hfx_potential_id, do_hfx_potential_truncated, do_hfx_potential_mix_cl_trunc/), &
         enum_desc=s2a("Coulomb potential: 1/r", &
                       "Shortrange potential: erfc(omega*r)/r", &
                       "Longrange potential: erf(omega*r)/r", &
                       "Mix coulomb and longrange potential: 1/r + erf(omega*r)/r", &
                       "Damped Gaussian potential: exp(-omega^2*r^2)", &
                       "Mix Gaussian and longrange potential: erf(omega*r)/r + exp(-omega^2*r^2)", &
                       "Overlap", &
                       "Truncated coulomb potential: if (r &lt; R_c) 1/r else 0", &
                       "Truncated Mix coulomb and longrange potential, assumes/requires that the erf has fully decayed at R_c"), &
         default_i_val=do_hfx_potential_coulomb)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      NULLIFY (keyword)
      CALL keyword_create( &
         keyword=keyword, &
         name="OMEGA", &
         description="Parameter for short/longrange interaction", &
         usage="OMEGA 0.5", &
         default_r_val=0.0_dp)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, name="SCALE_COULOMB", &
                          description="Scales Hartree-Fock contribution arising from a coulomb potential. "// &
                          "Only valid when doing a mixed potential calculation", &
                          usage="SCALE_COULOMB 1.0", default_r_val=1.0_dp)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, name="SCALE_LONGRANGE", &
                          description="Scales Hartree-Fock contribution arising from a longrange potential. "// &
                          "Only valid when doing a mixed potential calculation", &
                          usage="SCALE_LONGRANGE 1.0", default_r_val=1.0_dp)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, name="SCALE_GAUSSIAN", &
                          description="Scales Hartree-Fock contribution arising from a gaussian potential. "// &
                          "Only valid when doing a mixed potential calculation", &
                          usage="SCALE_GAUSSIAN 1.0", default_r_val=1.0_dp)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, name="CUTOFF_RADIUS", &
                          description="Determines cutoff radius for the truncated 1/r potential. "// &
                          "Only valid when doing truncated calculation", &
                          usage="CUTOFF_RADIUS 10.0", type_of_var=real_t, & ! default_r_val=10.0_dp,&
                          unit_str="angstrom")
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create( &
         keyword=keyword, &
         name="T_C_G_DATA", &
         description="Location of the file t_c_g.dat that contains the data for the "// &
         "evaluation of the truncated gamma function ", &
         usage="T_C_G_DATA /data/t_c_g.dat", &
         default_c_val="t_c_g.dat")
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

   END SUBROUTINE create_hf_potential_section

!****f* input_cp2k_dft/create_hf_screening_section [1.0] *

! **************************************************************************************************
!> \brief creates the input section for the hf screening part
!> \param section the section to create
!> \author Manuel Guidon
! **************************************************************************************************
   SUBROUTINE create_hf_screening_section(section)
      TYPE(section_type), POINTER                        :: section

      CHARACTER(len=*), PARAMETER :: routineN = 'create_hf_screening_section', &
         routineP = moduleN//':'//routineN

      TYPE(keyword_type), POINTER                        :: keyword

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, "SCREENING", &
                          description="Sets up screening parameters if requested ", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE., &
                          citations=(/guidon2008, guidon2009/))

      NULLIFY (keyword)
      CALL keyword_create( &
         keyword=keyword, &
         name="EPS_SCHWARZ", &
         description="Screens the near field part of the electronic repulsion "// &
         "integrals using the Schwarz inequality for the given "// &
         "threshold.", &
         usage="EPS_SCHWARZ 1.0E-6", &
         default_r_val=1.0E-10_dp)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      NULLIFY (keyword)
      CALL keyword_create( &
         keyword=keyword, &
         name="EPS_SCHWARZ_FORCES", &
         description="Screens the near field part of the electronic repulsion "// &
         "integrals using the Schwarz inequality for the given "// &
         "threshold. This will be approximately the accuracy of the forces, "// &
         " and should normally be similar to EPS_SCF", &
         usage="EPS_SCHWARZ_FORCES 1.0E-5", &
         default_r_val=1.0E-6_dp)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      NULLIFY (keyword)
      CALL keyword_create( &
         keyword=keyword, &
         name="SCREEN_P_FORCES", &
         description="Screens the electronic repulsion integrals for the forces "// &
         "using the density matrix. "// &
         "This results in a significant speedup for large systems, "// &
         "but might require a somewhat tigher EPS_SCHWARZ_FORCES.", &
         usage="SCREEN_P_FORCES TRUE", &
         default_l_val=.TRUE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      NULLIFY (keyword)
      CALL keyword_create(keyword, name="SCREEN_ON_INITIAL_P", &
                          description="Screen on an initial density matrix. For the first MD step"// &
                          " this matrix must be provided by a Restart File.", &
                          usage="SCREEN_ON_INITIAL_P  TRUE", default_l_val=.FALSE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      NULLIFY (keyword)
      CALL keyword_create(keyword, name="P_SCREEN_CORRECTION_FACTOR", &
                          description="Recalculates integrals on the fly if the actual density matrix is"// &
                          " larger by a given factor than the initial one. If the factor is set"// &
                          " to 0.0_dp, this feature is disabled.", &
                          usage="P_SCREEN_CORRECTION_FACTOR  0.0_dp", default_r_val=0.0_dp)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

   END SUBROUTINE create_hf_screening_section

! **************************************************************************************************
!> \brief creates the input section for the hf-pbc part
!> \param section the section to create
!> \author Manuel Guidon
! **************************************************************************************************
   SUBROUTINE create_hf_pbc_section(section)
      TYPE(section_type), POINTER                        :: section

      CHARACTER(len=*), PARAMETER :: routineN = 'create_hf_pbc_section', &
         routineP = moduleN//':'//routineN

      TYPE(keyword_type), POINTER                        :: keyword

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, "PERIODIC", &
                          description="Sets up periodic boundary condition parameters if requested ", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE., &
                          citations=(/guidon2008, guidon2009/))
      NULLIFY (keyword)
      CALL keyword_create( &
         keyword=keyword, &
         name="NUMBER_OF_SHELLS", &
         description="Number of shells taken into account for periodicity. "// &
         "By default, cp2k tries to automatically evaluate this number. "// &
         "This algorithm might be to conservative, resulting in some overhead. "// &
         "You can try to adjust this number in order to make a calculation cheaper. ", &
         usage="NUMBER_OF_SHELLS 2", &
         default_i_val=-1)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

   END SUBROUTINE create_hf_pbc_section

! **************************************************************************************************
!> \brief creates the input section for the hf-memory part
!> \param section the section to create
!> \author Manuel Guidon
! **************************************************************************************************
   SUBROUTINE create_hf_memory_section(section)
      TYPE(section_type), POINTER                        :: section

      CHARACTER(len=*), PARAMETER :: routineN = 'create_hf_memory_section', &
         routineP = moduleN//':'//routineN

      TYPE(keyword_type), POINTER                        :: keyword

      CPASSERT(.NOT. ASSOCIATED(section))
      CALL section_create(section, "MEMORY", &
                          description="Sets up memory parameters for the storage of the ERI's if requested ", &
                          n_keywords=1, n_subsections=0, repeats=.FALSE., &
                          citations=(/guidon2008/))
      NULLIFY (keyword)
      CALL keyword_create( &
         keyword=keyword, &
         name="EPS_STORAGE_SCALING", &
         variants=(/"EPS_STORAGE"/), &
         description="Scaling factor to scale eps_schwarz. Storage threshold for compression "// &
         "will be EPS_SCHWARZ*EPS_STORAGE_SCALING.", &
         usage="EPS_STORAGE 1.0E-2", &
         default_r_val=1.0E0_dp)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create( &
         keyword=keyword, &
         name="MAX_MEMORY", &
         description="Defines the maximum amount of memory [MiB] to be consumed by the full HFX module. "// &
         "All temporary buffers and helper arrays are subtracted from this number. "// &
         "What remains will be used for storage of integrals. NOTE: This number "// &
         "is assumed to represent the memory available to one MPI process. "// &
         "When running a threaded version, cp2k automatically takes care of "// &
         "distributing the memory among all the threads within a process.", &
         usage="MAX_MEMORY 256", &
         default_i_val=512)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create( &
         keyword=keyword, &
         name="STORAGE_LOCATION", &
         description="Loaction where ERI's are stored if MAX_DISK_SPACE /=0 "// &
         "Expects a path to a directory. ", &
         usage="STORAGE_LOCATION /data/scratch", &
         default_c_val=".")
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create( &
         keyword=keyword, &
         name="MAX_DISK_SPACE", &
         description="Defines the maximum amount of disk space [MiB] used to store precomputed "// &
         "compressed four-center integrals. If 0, nothing is stored to disk", &
         usage="MAX_DISK_SPACE 256", &
         default_i_val=0)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

      CALL keyword_create(keyword, name="TREAT_FORCES_IN_CORE", &
                          description="Determines whether the derivative ERI's should be stored to RAM or not. "// &
                          "Only meaningful when performing Ehrenfest MD. "// &
                          "Memory usage is defined via MAX_MEMORY, i.e. the memory is shared wit the energy ERI's.", &
                          usage="TREAT_FORCES_IN_CORE TRUE", default_l_val=.FALSE.)
      CALL section_add_keyword(section, keyword)
      CALL keyword_release(keyword)

   END SUBROUTINE create_hf_memory_section

END MODULE input_cp2k_hfx
