phase.F90

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!! Copyright (C) 2009 X. Andrade
!! Copyright (C) 2024 N. Tancogne-Dejean
!!
!! This program is free software; you can redistribute it and/or modify
!! it under the terms of the GNU General Public License as published by
!! the Free Software Foundation; either version 2, or (at your option)
!! any later version.
!!
!! This program is distributed in the hope that it will be useful,
!! but WITHOUT ANY WARRANTY; without even the implied warranty of
!! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
!! GNU General Public License for more details.
!!
!! You should have received a copy of the GNU General Public License
!! along with this program; if not, write to the Free Software
!! Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
!! 02110-1301, USA.
!!
 
#include "global.h"
 
module phase_oct_m
  use accel_oct_m
  use batch_oct_m
  use batch_ops_oct_m
  use comm_oct_m
  use debug_oct_m
  use derivatives_oct_m
  use distributed_oct_m
  use electron_space_oct_m
  use global_oct_m
  use grid_oct_m
  use hardware_oct_m
  use kpoints_oct_m
  use math_oct_m
  use mesh_oct_m
  use messages_oct_m
  use mpi_oct_m
  use profiling_oct_m
  use space_oct_m
  use states_elec_oct_m
  use states_elec_dim_oct_m
  use submesh_oct_m
  use types_oct_m
  use wfs_elec_oct_m
 
  implicit none
 
  private
 
  public ::                                         &
    phase_t
 
  type phase_t
    private
    complex(real64),         allocatable  :: phase(:, :)
    complex(real64), public,           allocatable  :: phase_corr(:,:)
    complex(real64),         allocatable  :: phase_spiral(:,:)
    type(accel_mem_t)                      :: buff_phase
    type(accel_mem_t)                      :: buff_phase_spiral
    type(accel_mem_t), public              :: buff_phase_corr
    integer                                :: buff_phase_qn_start
    real(real64), public,            pointer      :: spin(:,:,:) => null()
  contains
    procedure :: init => phase_init_phases
    
    procedure :: update => phase_update_phases
    
    procedure :: end => phase_end
    
    procedure :: set_phase_corr => phase_set_phase_corr
    
    procedure :: unset_phase_corr => phase_unset_phase_corr
    
    procedure :: apply_to => phase_apply_batch
    
    procedure :: apply_to_single => phase_apply_mf
    
    procedure :: apply_phase_spiral => phase_phase_spiral
    
    procedure :: is_allocated => phase_is_allocated
  end type phase_t
 
contains
 
  ! ---------------------------------------------------------
  subroutine phase_init_phases(phase, gr, kpt, kpoints, d, space)
    class(phase_t),          intent(inout) :: phase
    class(mesh_t),           intent(in)    :: gr
    type(distributed_t),     intent(in)    :: kpt
    type(kpoints_t),         intent(in)    :: kpoints
    type(states_elec_dim_t), intent(in)    :: d
    type(space_t),           intent(in)    :: space
 
    integer :: ip, ik, sp
    integer(int64) :: ip_inner_global
    real(real64)   :: kpoint(space%dim), x_global(space%dim)
 
    push_sub(phase_init_phases)
 
    ! no e^ik phase needed for Gamma-point-only periodic calculations
    ! unless for velocity-gauge for lasers
    if (accel_is_enabled()) then
      phase%buff_phase_qn_start = kpt%start
    end if
    if(kpoints%gamma_only()) then
      pop_sub(phase_init_phases)
      return
    end if
 
    safe_allocate(phase%phase(1:gr%np_part, kpt%start:kpt%end))
    safe_allocate(phase%phase_corr(gr%np+1:gr%np_part, kpt%start:kpt%end))
    !$omp parallel private(ip)
    do ik = kpt%start, kpt%end
      !$omp do
      do ip = gr%np + 1, gr%np_part
        phase%phase_corr(ip, ik) = m_one
      end do
      !$omp end do nowait
    end do
    !$omp end parallel
 
    ! Only when gr is a grid_t type, we can access gr%der
    select type(gr)
    class is(grid_t)
      if (gr%der%boundaries%spiralBC) then
        sp = gr%np
        if (gr%parallel_in_domains) sp = gr%np + gr%pv%np_ghost
 
        ! We decided to allocate the array from 1:np_part-sp as this is less error prone when passing
        ! the array to other routines, or in particular creating a C-style pointer from phase_spiral(1,1).
        ! We will also update phase_corr and possible other similar arrays.
 
        safe_allocate(phase%phase_spiral(1:gr%np_part-sp, 1:2))
 
        ! loop over boundary points
        do ip = sp + 1, gr%np_part
          ! get corresponding inner point
          ip_inner_global = mesh_periodic_point(gr, space, ip)
          x_global = mesh_x_global(gr, ip_inner_global)
          phase%phase_spiral(ip-sp, 1) = &
            exp(m_zi * sum((gr%x(ip, 1:space%dim)-x_global(1:space%dim)) * gr%der%boundaries%spiral_q(1:space%dim)))
          phase%phase_spiral(ip-sp, 2) = &
            exp(-m_zi * sum((gr%x(ip, 1:space%dim)-x_global(1:space%dim)) * gr%der%boundaries%spiral_q(1:space%dim)))
        end do
 
        if (accel_is_enabled()) then
          call accel_create_buffer(phase%buff_phase_spiral, accel_mem_read_only, type_cmplx, (gr%np_part-sp)*2)
          call accel_write_buffer(phase%buff_phase_spiral, gr%np_part-sp, 2, phase%phase_spiral)
        end if
      end if
    class default
      ! Do nothing
    end select
 
 
    kpoint(1:space%dim) = m_zero
 
    sp = gr%np
    if (gr%parallel_in_domains) sp = gr%np + gr%pv%np_ghost
 
    !$omp parallel private(ip, ip_inner_global, x_global, kpoint)
    do ik = kpt%start, kpt%end
      kpoint(1:space%dim) = kpoints%get_point(d%get_kpoint_index(ik))
      !$omp do
      do ip = 1, gr%np_part
        phase%phase(ip, ik) = exp(-m_zi * sum(gr%x(ip, 1:space%dim) * kpoint(1:space%dim)))
      end do
      !$omp end do
 
      ! loop over boundary points
      !$omp do
      do ip = sp + 1, gr%np_part
        ! get corresponding inner point
        ip_inner_global = mesh_periodic_point(gr, space, ip)
 
        ! compute phase correction from global coordinate (opposite sign!)
        x_global = mesh_x_global(gr, ip_inner_global)
        phase%phase_corr(ip, ik) = phase%phase(ip, ik)* &
          exp(m_zi * sum(x_global(1:space%dim) * kpoint(1:space%dim)))
      end do
      !$omp end do nowait
    end do
    !$omp end parallel
 
    if (accel_is_enabled()) then
      call accel_create_buffer(phase%buff_phase, accel_mem_read_write, type_cmplx, gr%np_part*kpt%nlocal)
      call accel_write_buffer(phase%buff_phase, gr%np_part, kpt%nlocal, phase%phase)
      call accel_create_buffer(phase%buff_phase_corr, accel_mem_read_write, type_cmplx, (gr%np_part - gr%np)*kpt%nlocal)
      call accel_write_buffer(phase%buff_phase_corr, gr%np_part - gr%np, kpt%nlocal, phase%phase_corr)
    end if
 
    pop_sub(phase_init_phases)
  end subroutine phase_init_phases
 
  ! ----------------------------------------------------------------------------------
  subroutine phase_update_phases(phase, mesh, kpt, kpoints, d, space, uniform_vector_potential)
    class(phase_t),      intent(inout) :: phase
    class(mesh_t),       intent(in)    :: mesh
    type(distributed_t), intent(in)    :: kpt
    type(kpoints_t),     intent(in)    :: kpoints
    type(states_elec_dim_t), intent(in)  :: d
    type(space_t),       intent(in)    :: space
    real(real64), allocatable,  intent(in)    :: uniform_vector_potential(:)
 
    integer :: ik, ip, sp, wgsize
    integer(int64) :: ip_inner_global
    real(real64)   :: kpoint(space%dim)
    real(real64), allocatable :: x_global(:,:), kpt_vec_pot(:,:), x(:,:)
    type(accel_mem_t) :: buff_vec_pot, buff_x_global, buff_x
    type(accel_kernel_t), save :: kernel
    real(real64) :: tmp_sum
 
    if (.not. allocated(uniform_vector_potential)) return
 
    push_sub_with_profile(phase_update_phases)
 
 
    if (.not. allocated(phase%phase)) then
      safe_allocate(phase%phase(1:mesh%np_part, kpt%start:kpt%end))
      if (accel_is_enabled()) then
        call accel_create_buffer(phase%buff_phase, accel_mem_read_write, type_cmplx, &
          mesh%np_part*kpt%nlocal)
      end if
    end if
 
    if (.not. allocated(phase%phase_corr)) then
      safe_allocate(phase%phase_corr(mesh%np+1:mesh%np_part, kpt%start:kpt%end))
      if (accel_is_enabled()) then
        call accel_create_buffer(phase%buff_phase_corr, accel_mem_read_write, type_cmplx, &
          (mesh%np_part - mesh%np)*kpt%nlocal)
      end if
    end if
 
    ! TODO: We should not recompute this every time-step. We should store it.
 
    ! loop over boundary points
    sp = mesh%np
    ! skip ghost points
    if (mesh%parallel_in_domains) sp = mesh%np + mesh%pv%np_ghost
 
    safe_allocate(x_global(1:space%dim,(sp + 1):mesh%np_part))
 
    ! TODO: Introduce a permanent value and start replacing mesh%x by mesh%x_trans
    safe_allocate(x(1:space%dim, 1:mesh%np_part))
    x = transpose(mesh%x)
 
    !$omp parallel do schedule(static) private(ip_inner_global)
    do ip = sp + 1, mesh%np_part
      ! get corresponding inner point
      ip_inner_global = mesh_periodic_point(mesh, space, ip)
      ! compute the difference between the global coordinate and the local coordinate
      x_global(:,ip) = mesh_x_global(mesh, ip_inner_global) - mesh%x(ip, 1:space%dim)
    end do
 
 
    if (.not. accel_is_enabled()) then
      !$omp parallel private(ik, ip, kpoint, tmp_sum)
      do ik = kpt%start, kpt%end
        kpoint(1:space%dim) = kpoints%get_point(d%get_kpoint_index(ik))
        !We add the vector potential
        kpoint(1:space%dim) = kpoint(1:space%dim) + uniform_vector_potential(1:space%dim)
 
        !$omp do schedule(static)
        do ip = 1, mesh%np_part
          tmp_sum = sum(x(1:space%dim, ip)*kpoint(1:space%dim))
          phase%phase(ip, ik) = cmplx(cos(tmp_sum), -sin(tmp_sum), real64)
        end do
        !$omp end do
 
        !$omp do schedule(static)
        do ip = sp + 1, mesh%np_part
          tmp_sum = sum(x_global(1:space%dim, ip)*kpoint(1:space%dim))
          phase%phase_corr(ip, ik) = cmplx(cos(tmp_sum), sin(tmp_sum), real64)
        end do
        !$omp end do nowait
      end do
      !$omp end parallel
 
    else !accel_is enabled
 
      call accel_create_buffer(buff_vec_pot, accel_mem_read_only, type_float, space%dim*kpt%nlocal)
      safe_allocate(kpt_vec_pot(1:space%dim,kpt%start:kpt%end))
      do ik = kpt%start, kpt%end
        kpoint(1:space%dim) = kpoints%get_point(d%get_kpoint_index(ik))
        kpt_vec_pot(1:space%dim, ik) = kpoint(1:space%dim) + uniform_vector_potential(1:space%dim)
      end do
      call accel_write_buffer(buff_vec_pot, space%dim, kpt%nlocal, kpt_vec_pot, async=.true.)
 
      ! Note: this should be globally stored
      call accel_create_buffer(buff_x, accel_mem_read_only, type_float, space%dim*(mesh%np_part))
      call accel_write_buffer(buff_x, space%dim, mesh%np_part, x, async=.true.)
 
      call accel_create_buffer(buff_x_global, accel_mem_read_only, type_float, space%dim*(mesh%np_part-sp))
      call accel_write_buffer(buff_x_global, space%dim, mesh%np_part-sp, x_global(1:space%dim,(sp + 1):mesh%np_part), async=.true.)
 
      call accel_kernel_start_call(kernel, 'phase.cl', 'update_phases')
 
      call accel_set_kernel_arg(kernel, 0, space%dim)
      call accel_set_kernel_arg(kernel, 1, mesh%np)
      call accel_set_kernel_arg(kernel, 2, mesh%np_part)
      call accel_set_kernel_arg(kernel, 3, kpt%start)
      call accel_set_kernel_arg(kernel, 4, kpt%end)
      call accel_set_kernel_arg(kernel, 5, sp)
      call accel_set_kernel_arg(kernel, 6, buff_vec_pot)
      call accel_set_kernel_arg(kernel, 7, buff_x)
      call accel_set_kernel_arg(kernel, 8, buff_x_global)
      call accel_set_kernel_arg(kernel, 9, phase%buff_phase)
      call accel_set_kernel_arg(kernel, 10, phase%buff_phase_corr)
 
      wgsize = accel_kernel_workgroup_size(kernel)
 
      call accel_kernel_run(kernel, (/pad(mesh%np_part, wgsize), kpt%nlocal/), (/wgsize, 1/))
 
      call accel_read_buffer(phase%buff_phase, mesh%np_part, kpt%nlocal, phase%phase, async=.true.)
      call accel_read_buffer(phase%buff_phase_corr, mesh%np_part - mesh%np, kpt%nlocal, phase%phase_corr)
 
      call accel_release_buffer(buff_vec_pot)
      call accel_release_buffer(buff_x)
      call accel_release_buffer(buff_x_global)
      safe_deallocate_a(kpt_vec_pot)
    end if
 
    safe_deallocate_a(x_global)
    safe_deallocate_a(x)
 
    pop_sub_with_profile(phase_update_phases)
  end subroutine phase_update_phases
 
  ! ----------------------------------------------------------------------------------
  subroutine phase_end(phase)
    class(phase_t),  intent(inout) :: phase
 
    push_sub(phase_end)
 
    if (phase%is_allocated() .and. accel_is_enabled()) then
      call accel_release_buffer(phase%buff_phase)
      call accel_release_buffer(phase%buff_phase_corr)
    end if
 
    if (allocated(phase%phase_spiral) .and. accel_is_enabled()) then
      call accel_release_buffer(phase%buff_phase_spiral)
    end if
 
    safe_deallocate_a(phase%phase)
    safe_deallocate_a(phase%phase_corr)
    safe_deallocate_a(phase%phase_spiral)
 
    pop_sub(phase_end)
  end subroutine phase_end
 
  ! ----------------------------------------------------------------------------------
  !
  subroutine phase_set_phase_corr(phase, mesh, psib, async)
    class(phase_t),                intent(in) :: phase
    class(mesh_t),                 intent(in) :: mesh
    type(wfs_elec_t),           intent(inout) :: psib
    logical, optional,             intent(in) :: async
 
 
    logical :: phase_correction
 
    push_sub(phase_set_phase_corr)
 
    ! check if we only want a phase correction for the boundary points
    phase_correction = phase%is_allocated()
 
    !We apply the phase only to np points, and the phase for the np+1 to np_part points
    !will be treated as a phase correction in the Hamiltonian
    if (phase_correction) then
      call phase%apply_to(mesh, mesh%np, .false., psib, async=async)
    end if
 
    pop_sub(phase_set_phase_corr)
  end subroutine phase_set_phase_corr
 
  ! ----------------------------------------------------------------------------------
  !
  subroutine phase_unset_phase_corr(phase, mesh, psib, async)
    class(phase_t),                intent(in) :: phase
    class(mesh_t),                 intent(in) :: mesh
    type(wfs_elec_t),           intent(inout) :: psib
    logical, optional,             intent(in) :: async
 
    logical :: phase_correction
 
    push_sub(phase_unset_phase_corr)
 
    ! check if we only want a phase correction for the boundary points
    phase_correction = phase%is_allocated()
 
    !We apply the phase only to np points, and the phase for the np+1 to np_part points
    !will be treated as a phase correction in the Hamiltonian
    if (phase_correction) then
      call phase%apply_to(mesh, mesh%np, .true., psib, async=async)
    end if
 
    pop_sub(phase_unset_phase_corr)
  end subroutine phase_unset_phase_corr
 
  ! ---------------------------------------------------------------------------------------
  !
  subroutine phase_apply_batch(this, mesh, np, conjugate, psib, src, async)
    class(phase_t),                        intent(in)    :: this
    class(mesh_t),                         intent(in)    :: mesh
    integer,                               intent(in)    :: np
    logical,                               intent(in)    :: conjugate
    type(wfs_elec_t),              target, intent(inout) :: psib
    type(wfs_elec_t),    optional, target, intent(in)    :: src
    logical, optional,                     intent(in)    :: async
 
    integer :: ip, ii, sp
    type(wfs_elec_t), pointer :: src_
    complex(real64) :: phase
    integer(int64) :: wgsize, dim2, dim3
    type(accel_kernel_t), save :: ker_phase
 
    push_sub(phase_apply_batch)
    call profiling_in("PHASE_APPLY_BATCH")
 
    call profiling_count_operations(6*np*psib%nst_linear)
 
    assert(np <= mesh%np_part)
    assert(psib%type() == type_cmplx)
    assert(psib%ik >= lbound(this%phase, dim=2))
    assert(psib%ik <= ubound(this%phase, dim=2))
 
    src_ => psib
    if (present(src)) src_ => src
 
    assert(src_%has_phase .eqv. conjugate)
    assert(src_%ik == psib%ik)
    assert(src_%type() == type_cmplx)
 
    ! We want to skip the ghost points for setting the phase
    sp = min(np, mesh%np)
    if (np > mesh%np .and. mesh%parallel_in_domains) sp = mesh%np + mesh%pv%np_ghost
 
    select case (psib%status())
    case (batch_packed)
 
      if (conjugate) then
 
        !$omp parallel private(ii, phase)
        !$omp do
        do ip = 1, min(mesh%np, np)
          phase = conjg(this%phase(ip, psib%ik))
          !$omp simd
          do ii = 1, psib%nst_linear
            psib%zff_pack(ii, ip) = phase*src_%zff_pack(ii, ip)
          end do
        end do
        !$omp end do nowait
 
        ! Boundary points, if requested
        !$omp do
        do ip = sp+1, np
          phase = conjg(this%phase(ip, psib%ik))
          !$omp simd
          do ii = 1, psib%nst_linear
            psib%zff_pack(ii, ip) = phase*src_%zff_pack(ii, ip)
          end do
        end do
        !$omp end parallel
 
      else
 
        !$omp parallel private(ii, phase)
        !$omp do
        do ip = 1, min(mesh%np, np)
          phase = this%phase(ip, psib%ik)
          !$omp simd
          do ii = 1, psib%nst_linear
            psib%zff_pack(ii, ip) = phase*src_%zff_pack(ii, ip)
          end do
        end do
        !$omp end do nowait
 
        ! Boundary points, if requested
        !$omp do
        do ip = sp+1, np
          phase = this%phase(ip, psib%ik)
          !$omp simd
          do ii = 1, psib%nst_linear
            psib%zff_pack(ii, ip) = phase*src_%zff_pack(ii, ip)
          end do
        end do
        !$omp end parallel
 
      end if
 
    case (batch_not_packed)
 
      if (conjugate) then
 
        !$omp parallel private(ii, ip)
        do ii = 1, psib%nst_linear
          !$omp do simd
          do ip = 1, min(mesh%np, np)
            psib%zff_linear(ip, ii) = conjg(this%phase(ip, psib%ik))*src_%zff_linear(ip, ii)
          end do
          !$omp end do simd nowait
 
          ! Boundary points, if requested
          !$omp do simd
          do ip = sp+1, np
            psib%zff_linear(ip, ii) = conjg(this%phase(ip, psib%ik))*src_%zff_linear(ip, ii)
          end do
          !$omp end do simd nowait
        end do
        !$omp end parallel
 
      else
        !$omp parallel private(ii, ip)
        do ii = 1, psib%nst_linear
          !$omp do simd
          do ip = 1, min(mesh%np, np)
            psib%zff_linear(ip, ii) = this%phase(ip, psib%ik)*src_%zff_linear(ip, ii)
          end do
          !$omp end do simd nowait
 
          ! Boundary points, if requested
          !$omp do simd
          do ip = sp+1, np
            psib%zff_linear(ip, ii) = this%phase(ip, psib%ik)*src_%zff_linear(ip, ii)
          end do
          !$omp end do simd nowait
 
        end do
        !$omp end parallel
 
      end if
 
    case (batch_device_packed)
      call accel_kernel_start_call(ker_phase, 'phase.cl', 'phase_hamiltonian')
 
      if (conjugate) then
        call accel_set_kernel_arg(ker_phase, 0, 1_4)
      else
        call accel_set_kernel_arg(ker_phase, 0, 0_4)
      end if
 
      call accel_set_kernel_arg(ker_phase, 1, (psib%ik - this%buff_phase_qn_start)*mesh%np_part)
      call accel_set_kernel_arg(ker_phase, 2, np)
      call accel_set_kernel_arg(ker_phase, 3, this%buff_phase)
      call accel_set_kernel_arg(ker_phase, 4, src_%ff_device)
      call accel_set_kernel_arg(ker_phase, 5, log2(int(src_%pack_size(1), int32)))
      call accel_set_kernel_arg(ker_phase, 6, psib%ff_device)
      call accel_set_kernel_arg(ker_phase, 7, log2(int(psib%pack_size(1), int32)))
 
      wgsize = accel_kernel_workgroup_size(ker_phase)/psib%pack_size(1)
 
      dim3 = np/(accel_max_size_per_dim(2)*wgsize) + 1
      dim2 = min(accel_max_size_per_dim(2)*wgsize, pad(np, wgsize))
 
      call accel_kernel_run(ker_phase, (/psib%pack_size(1), dim2, dim3/), (/psib%pack_size(1), wgsize, 1_int64/))
 
      if(.not. optional_default(async, .false.)) call accel_finish()
    end select
 
    psib%has_phase = .not. conjugate
 
    call profiling_out("PHASE_APPLY_BATCH")
    pop_sub(phase_apply_batch)
  end subroutine phase_apply_batch
 
  !
  subroutine phase_apply_mf(this, psi, np, dim, ik, conjugate)
    class(phase_t),         intent(in)    :: this
    complex(real64),     intent(inout)    :: psi(:, :)
    integer,                intent(in)    :: np
    integer,                intent(in)    :: dim
    integer,                intent(in)    :: ik
    logical,                intent(in)    :: conjugate
 
    integer :: idim, ip
 
    push_sub(phase_apply_mf)
 
    assert(ik >= lbound(this%phase, dim=2))
    assert(ik <= ubound(this%phase, dim=2))
 
    call profiling_in("PHASE_APPLY_SINGLE")
 
    if (conjugate) then
      ! Apply the phase that contains both the k-point and vector-potential terms.
      do idim = 1, dim
        !$omp parallel do
        do ip = 1, np
          psi(ip, idim) = conjg(this%phase(ip, ik))*psi(ip, idim)
        end do
        !$omp end parallel do
      end do
    else
      ! Apply the conjugate of (i.e. remove) the phase that contains both the k-point and vector-potential terms.
      do idim = 1, dim
        !$omp parallel do
        do ip = 1, np
          psi(ip, idim) = this%phase(ip, ik)*psi(ip, idim)
        end do
        !$omp end parallel do
      end do
    end if
 
    call profiling_out("PHASE_APPLY_SINGLE")
 
    pop_sub(phase_apply_mf)
  end subroutine phase_apply_mf
 
 
  ! ---------------------------------------------------------------------------------------
  !
  subroutine phase_phase_spiral(this, der, psib)
    class(phase_t),         intent(in)    :: this
    type(derivatives_t),    intent(in)    :: der
    class(wfs_elec_t),      intent(inout) :: psib
 
    integer               :: ip, ii, sp
    integer, allocatable  :: spin_label(:)
    type(accel_mem_t)     :: spin_label_buffer
    integer(int64) :: wgsize
 
    push_sub(phase_phase_spiral)
    call profiling_in("PBC_PHASE_SPIRAL")
 
    call profiling_count_operations(6*(der%mesh%np_part-der%mesh%np)*psib%nst_linear)
 
    assert(der%boundaries%spiral)
    assert(psib%type() == type_cmplx)
 
    sp = der%mesh%np
    if (der%mesh%parallel_in_domains) sp = der%mesh%np + der%mesh%pv%np_ghost
 
 
    select case (psib%status())
    case (batch_packed)
 
      !$omp parallel do private(ip, ii)
      do ip = sp + 1, der%mesh%np_part
        do ii = 1, psib%nst_linear, 2
          if (this%spin(3,psib%linear_to_ist(ii), psib%ik)>0) then
            psib%zff_pack(ii+1, ip) = psib%zff_pack(ii+1, ip)*this%phase_spiral(ip-sp, 1)
          else
            psib%zff_pack(ii, ip) = psib%zff_pack(ii, ip)*this%phase_spiral(ip-sp, 2)
          end if
        end do
      end do
      !$omp end parallel do
 
    case (batch_not_packed)
 
      !$omp parallel private(ii, ip)
      do ii = 1, psib%nst_linear, 2
        if (this%spin(3,psib%linear_to_ist(ii), psib%ik)>0) then
          !$omp do
          do ip = sp + 1, der%mesh%np_part
            psib%zff_linear(ip, ii+1) = psib%zff_linear(ip, ii+1)*this%phase_spiral(ip-sp, 1)
          end do
          !$omp end do nowait
        else
          !$omp do
          do ip = sp + 1, der%mesh%np_part
            psib%zff_linear(ip, ii) = psib%zff_linear(ip, ii)*this%phase_spiral(ip-sp, 2)
          end do
          !$omp end do nowait
        end if
      end do
      !$omp end parallel
 
    case (batch_device_packed)
 
      assert(accel_is_enabled())
 
      ! generate array of offsets for access of psib and phase_spiral:
      ! TODO: Move this to the routine where spin(:,:,:) is generated
      !       and also move the buffer to the GPU at this point to
      !       avoid unecessary latency here!
 
      safe_allocate(spin_label(1:psib%nst_linear))
      spin_label = 0
      do ii = 1, psib%nst_linear, 2
        if (this%spin(3, psib%linear_to_ist(ii), psib%ik) > 0) spin_label(ii)=1
      end do
 
      call accel_create_buffer(spin_label_buffer, accel_mem_read_only, type_integer, psib%nst_linear)
      call accel_write_buffer(spin_label_buffer, psib%nst_linear, spin_label)
 
      call accel_kernel_start_call(kernel_phase_spiral, 'phase_spiral.cl', 'phase_spiral_apply')
 
      call accel_set_kernel_arg(kernel_phase_spiral, 0, psib%nst)
      call accel_set_kernel_arg(kernel_phase_spiral, 1, sp)
      call accel_set_kernel_arg(kernel_phase_spiral, 2, der%mesh%np_part)
      call accel_set_kernel_arg(kernel_phase_spiral, 3, psib%ff_device)
      call accel_set_kernel_arg(kernel_phase_spiral, 4, log2(psib%pack_size(1)))
      call accel_set_kernel_arg(kernel_phase_spiral, 5, this%buff_phase_spiral)
      call accel_set_kernel_arg(kernel_phase_spiral, 6, spin_label_buffer)
 
      wgsize = accel_kernel_workgroup_size(kernel_phase_spiral)/psib%pack_size(1)
 
      call accel_kernel_run(kernel_phase_spiral, &
        (/psib%pack_size(1)/2, pad(der%mesh%np_part - sp, 2*wgsize)/), &
        (/psib%pack_size(1)/2, 2*wgsize/))
 
      call accel_finish()
 
      call accel_release_buffer(spin_label_buffer)
 
      safe_deallocate_a(spin_label)
 
    end select
 
    call profiling_out("PBC_PHASE_SPIRAL")
    pop_sub(phase_phase_spiral)
  end subroutine phase_phase_spiral
 
 
  ! ---------------------------------------------------------------------------------------
  logical pure function phase_is_allocated(this)
    class(phase_t), intent(in) :: this
 
    phase_is_allocated = allocated(this%phase)
  end function phase_is_allocated
 
end module phase_oct_m
 
!! Local Variables:
!! mode: f90
!! coding: utf-8
!! End: