P3MFFTBackend< FloatType, FFTConfig > Struct Template Reference

Abstract interface for the P3M reciprocal-space FFT. More...

#include <P3MFFTBackend.hpp>

Inheritance diagram for P3MFFTBackend< FloatType, FFTConfig >:

Public Types
using	ComplexType = std::complex< FloatType >
using	RSpaceScalar = FloatType
	Real-space scalar type.

Public Member Functions
virtual	~P3MFFTBackend ()=default
virtual Utils::Vector3i	ks_local_ld_index () const =0
	Lower-left corner of this rank's k-space box (global coords).
virtual Utils::Vector3i	ks_local_ur_index () const =0
	Upper-right corner (exclusive) of this rank's k-space box.
virtual Utils::Vector3i	ks_local_size () const =0
	Extent of this rank's k-space box.
virtual Utils::Vector3i	rs_local_size () const =0
	Extent of this rank's real-space (no-halo) box.
virtual RSpaceScalar *	forward_input_buffer ()=0
	Persistent, transform-ready buffer for the caller to fill with the no-halo real-space input; holds product(rs_local_size()) elements.
virtual void	forward (RSpaceScalar const *in, ComplexType *out)=0
	Forward transform (real/complex charge density to k-space).
virtual void	backward (ComplexType *in, RSpaceScalar *out)=0
	Backward transform (k-space field to real space).

Detailed Description

template<typename FloatType, class FFTConfig>
struct P3MFFTBackend< FloatType, FFTConfig >

Abstract interface for the P3M reciprocal-space FFT.

P3M only ever touches the FFT through this handful of methods: the k-space box geometry accessors and the forward/backward transforms. Concrete backends (heFFTe for the general/distributed case, kokkos-fft for the single-rank case) implement it, so the solver is agnostic to which one is active. The transform buffers are flat, contiguous, no-halo arrays; halo exchange is handled outside the FFT.

Definition at line 37 of file P3MFFTBackend.hpp.

Member Typedef Documentation

ComplexType

template<typename FloatType , class FFTConfig >

using P3MFFTBackend< FloatType, FFTConfig >::ComplexType = std::complex<FloatType>

Definition at line 38 of file P3MFFTBackend.hpp.

RSpaceScalar

template<typename FloatType , class FFTConfig >

using P3MFFTBackend< FloatType, FFTConfig >::RSpaceScalar = FloatType

Real-space scalar type.

P3M's real-space buffers (charge density, E-field) are physically real in both configs, so this is always FloatType. For a c2c backend (use_r2c=false) the imaginary part is dropped on the backward transform via heFFTe's real-output convenience overload, matching the pre-backend-interface behaviour where the templated forward/backward transforms of P3MFFT accepted real pointers for either config.

Definition at line 47 of file P3MFFTBackend.hpp.

Constructor & Destructor Documentation

~P3MFFTBackend()

template<typename FloatType , class FFTConfig >

virtual P3MFFTBackend< FloatType, FFTConfig >::~P3MFFTBackend ( )

virtualdefault

Member Function Documentation

backward()

template<typename FloatType , class FFTConfig >

virtual void P3MFFTBackend< FloatType, FFTConfig >::backward ( ComplexType *  in, RSpaceScalar *  out  )

pure virtual

Backward transform (k-space field to real space).

The input buffer is non-const by contract: a backend may destroy it during the transform (FFTW's multi-dimensional c2r has no preserve-input mode, so the kokkos-fft backend runs it in place). Callers must recompute the k-space input before reading it again.

Implemented in P3MFFTHeffte< FloatType, FFTConfig >.

forward()

template<typename FloatType , class FFTConfig >

virtual void P3MFFTBackend< FloatType, FFTConfig >::forward ( RSpaceScalar const *  in, ComplexType *  out  )

pure virtual

Forward transform (real/complex charge density to k-space).

Implemented in P3MFFTHeffte< FloatType, FFTConfig >.

forward_input_buffer()

template<typename FloatType , class FFTConfig >

virtual RSpaceScalar * P3MFFTBackend< FloatType, FFTConfig >::forward_input_buffer ( )

pure virtual

Persistent, transform-ready buffer for the caller to fill with the no-halo real-space input; holds product(rs_local_size()) elements.

Passing it back as forward's in lets a backend transform it in place.

Implemented in P3MFFTHeffte< FloatType, FFTConfig >.

ks_local_ld_index()

template<typename FloatType , class FFTConfig >

virtual Utils::Vector3i P3MFFTBackend< FloatType, FFTConfig >::ks_local_ld_index ( ) const

pure virtual

Lower-left corner of this rank's k-space box (global coords).

Implemented in P3MFFTHeffte< FloatType, FFTConfig >.

ks_local_size()

template<typename FloatType , class FFTConfig >

virtual Utils::Vector3i P3MFFTBackend< FloatType, FFTConfig >::ks_local_size ( ) const

pure virtual

Extent of this rank's k-space box.

Implemented in P3MFFTHeffte< FloatType, FFTConfig >.

ks_local_ur_index()

template<typename FloatType , class FFTConfig >

virtual Utils::Vector3i P3MFFTBackend< FloatType, FFTConfig >::ks_local_ur_index ( ) const

pure virtual

Upper-right corner (exclusive) of this rank's k-space box.

Implemented in P3MFFTHeffte< FloatType, FFTConfig >.

rs_local_size()

template<typename FloatType , class FFTConfig >

virtual Utils::Vector3i P3MFFTBackend< FloatType, FFTConfig >::rs_local_size ( ) const

pure virtual

Extent of this rank's real-space (no-halo) box.

Implemented in P3MFFTHeffte< FloatType, FFTConfig >.

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The documentation for this struct was generated from the following file:

• P3MFFTBackend.hpp