Batched lattice Fourier transforms on regular k-point grids. More...

Data Types
type	k_grid_to_cell_work_type

Functions/Subroutines
logical function, public	regular_kpoint_grid (xkp, nkp_grid, grid_index, k_offset, allow_incomplete)
	Test and map a uniformly shifted reciprocal grid or an explicitly allowed subset.
logical function, public	lattice_fft_shape (n, nfft, allow_arbitrary)
	Find backend-supported FFT dimensions that preserve the original lattice grid. Sample the padded transform at integer multiples of the original cell indices.
subroutine, public	cell_to_k_grid_fft (values_rs, index_to_cell, xkp, nkp_grid, values_k, used_fft, deriv_direction, hmat, selected_kpoints)
	Transform a batch of real matrices from image cells to every supplied k point.
subroutine, public	k_grid_to_cell_fft (values_k, xkp, nkp_grid, index_to_cell, values_rs, used_fft, weights, allow_incomplete)
	Transform reciprocal-grid data back to image-cell values.
subroutine, public	k_grid_to_cell_prepare (work, xkp, nkp_grid, index_to_cell, weights, allow_incomplete)
	Prepare one inverse lattice transform for repeated matrix batches.
subroutine, public	k_grid_to_cell_execute (work, values_k, values_rs, used_fft)
	Execute a matrix batch using the prepared inverse lattice transform. Call outside OpenMP worker regions: fft_tools owns its shared pool and planner.
subroutine, public	k_grid_to_cell_release (work)
	Release call-scoped inverse lattice maps and FFT buffers.

Detailed Description

Batched lattice Fourier transforms on regular k-point grids.

  Image cells are folded modulo the reciprocal grid; shifted meshes use a phase twist.
  Forward transforms require a complete grid. The inverse transform can also embed
  an explicitly allowed subset with its supplied weights and zero missing points.
  Unsupported grids retain the direct phase-sum fallback.

Function/Subroutine Documentation

◆ regular_kpoint_grid()

logical function, public kpoint_lattice_fft::regular_kpoint_grid	(	real(kind=dp), dimension(:, :), intent(in)	xkp,
		integer, dimension(3), intent(in)	nkp_grid,
		integer, dimension(:, :), intent(out), optional	grid_index,
		real(kind=dp), dimension(3), intent(out), optional	k_offset,
		logical, intent(in), optional	allow_incomplete )

Test and map a uniformly shifted reciprocal grid or an explicitly allowed subset.

Parameters

xkp	reciprocal coordinates, in units of reciprocal lattice vectors
nkp_grid	regular-grid dimensions
grid_index	FFT-grid index for every k point
k_offset	common reciprocal-coordinate offset
allow_incomplete	accept a subset of a regular grid (missing points are zero)

Returns: true for a regular grid, complete unless allow_incomplete is set

Definition at line 66 of file kpoint_lattice_fft.F.

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◆ lattice_fft_shape()

logical function, public kpoint_lattice_fft::lattice_fft_shape	(	integer, dimension(3), intent(in)	n,
		integer, dimension(3), intent(out)	nfft,
		logical, intent(in), optional	allow_arbitrary )

Find backend-supported FFT dimensions that preserve the original lattice grid. Sample the padded transform at integer multiples of the original cell indices.

Parameters

n	original grid dimensions
nfft	supported integer multiples, if available
allow_arbitrary	use exact dimensions when supported by the active FFT backend

Returns: whether all dimensions have a supported multiple

Definition at line 125 of file kpoint_lattice_fft.F.

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◆ cell_to_k_grid_fft()

subroutine, public kpoint_lattice_fft::cell_to_k_grid_fft	(	real(kind=dp), dimension(:, :, :), intent(in)	values_rs,
		integer, dimension(:, :), intent(in)	index_to_cell,
		real(kind=dp), dimension(:, :), intent(in)	xkp,
		integer, dimension(3), intent(in)	nkp_grid,
		complex(kind=dp), dimension(:, :, :), intent(out)	values_k,
		logical, intent(out), optional	used_fft,
		integer, intent(in), optional	deriv_direction,
		real(kind=dp), dimension(3, 3), intent(in), optional	hmat,
		integer, dimension(:), intent(in), optional	selected_kpoints )

Transform a batch of real matrices from image cells to every supplied k point.

Parameters

values_rs	real-space matrices; the last dimension enumerates image cells
index_to_cell	integer lattice vector for every image cell
xkp	reciprocal coordinates of all requested k points
nkp_grid	dimensions of the candidate regular reciprocal grid
values_k	complex matrices at every k point
used_fft	reports whether the regular-grid FFT path was used
deriv_direction	optional Cartesian k derivative (1, 2, or 3)
hmat	direct-lattice cell matrix, required for a derivative
selected_kpoints	optional indices of k points to retain in values_k

Definition at line 169 of file kpoint_lattice_fft.F.

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◆ k_grid_to_cell_fft()

subroutine, public kpoint_lattice_fft::k_grid_to_cell_fft	(	complex(kind=dp), dimension(:, :, :), intent(in)	values_k,
		real(kind=dp), dimension(:, :), intent(in)	xkp,
		integer, dimension(3), intent(in)	nkp_grid,
		integer, dimension(:, :), intent(in)	index_to_cell,
		complex(kind=dp), dimension(:, :, :), intent(out)	values_rs,
		logical, intent(out), optional	used_fft,
		real(kind=dp), dimension(:), intent(in), optional	weights,
		logical, intent(in), optional	allow_incomplete )

Transform reciprocal-grid data back to image-cell values.

Parameters

values_k	complex matrices on the supplied reciprocal points
xkp	reciprocal coordinates, in units of reciprocal lattice vectors
nkp_grid	dimensions of the reciprocal grid
index_to_cell	integer lattice vector for every requested image cell
values_rs	reconstructed complex matrices in the requested image cells
used_fft	reports whether the regular-grid FFT path was used
weights	optional k weights; otherwise use the existing 1/number-of-points normalization
allow_incomplete	embed a unique regular-grid subset, zero-filling missing points

Definition at line 296 of file kpoint_lattice_fft.F.

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◆ k_grid_to_cell_prepare()

subroutine, public kpoint_lattice_fft::k_grid_to_cell_prepare	(	type(k_grid_to_cell_work_type), intent(inout)	work,
		real(kind=dp), dimension(:, :), intent(in)	xkp,
		integer, dimension(3), intent(in)	nkp_grid,
		integer, dimension(:, :), intent(in)	index_to_cell,
		real(kind=dp), dimension(:), intent(in), optional	weights,
		logical, intent(in), optional	allow_incomplete )

Prepare one inverse lattice transform for repeated matrix batches.

Parameters

work	call-scoped maps, weights and buffers; no backend plan ownership
xkp	reciprocal coordinates
nkp_grid	candidate reciprocal-grid dimensions
index_to_cell	requested lattice translations
weights	final k weights, otherwise 1/number-of-points
allow_incomplete	allow missing grid points, with zero values

Definition at line 325 of file kpoint_lattice_fft.F.

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◆ k_grid_to_cell_execute()

subroutine, public kpoint_lattice_fft::k_grid_to_cell_execute	(	type(k_grid_to_cell_work_type), intent(inout)	work,
		complex(kind=dp), dimension(:, :, :), intent(in)	values_k,
		complex(kind=dp), dimension(:, :, :), intent(out)	values_rs,
		logical, intent(out), optional	used_fft )

Execute a matrix batch using the prepared inverse lattice transform. Call outside OpenMP worker regions: fft_tools owns its shared pool and planner.

Parameters

work	prepared transform; scratch is reused, never shared between concurrent callers
values_k	matrices at the prepared reciprocal points
values_rs	matrices at the prepared lattice translations
used_fft	whether this batch used FFT, including execution failure fallback

Definition at line 376 of file kpoint_lattice_fft.F.

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◆ k_grid_to_cell_release()

subroutine, public kpoint_lattice_fft::k_grid_to_cell_release ( type(k_grid_to_cell_work_type), intent(inout) work )

Release call-scoped inverse lattice maps and FFT buffers.

Parameters

work ...

Definition at line 428 of file kpoint_lattice_fft.F.

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Data Types

Functions/Subroutines

Detailed Description

Function/Subroutine Documentation

◆ regular_kpoint_grid()

◆ lattice_fft_shape()

◆ cell_to_k_grid_fft()

◆ k_grid_to_cell_fft()

◆ k_grid_to_cell_prepare()

◆ k_grid_to_cell_execute()

◆ k_grid_to_cell_release()