amrex::FFT Namespace Reference

Classes
class	CrossProj
	FFT-based projection of a cell-centered velocity field onto the space of fields that are divergence free with respect to the node-centered cross-stencil divergence. More...
struct	Info
struct	Plan
class	LocalR2C
	Local Discrete Fourier Transform. More...
class	OpenBCSolver
	Convolution-based solver for open boundary conditions using Green's functions. More...
class	Poisson
	Poisson solver for periodic, Dirichlet & Neumann boundaries using FFT. More...
class	PoissonOpenBC
	Poisson solve for Open BC using FFT. More...
class	PoissonHybrid
	3D Poisson solver for periodic, Dirichlet & Neumann boundaries in the first two dimensions, and Dirichlet & Neumann in the last dimension. The last dimension could have non-uniform mesh. More...
class	R2C
	Parallel Discrete Fourier Transform. More...
class	R2X
	Discrete Fourier Transform. More...
class	Stokes
	Stokes solver for periodic domains using FFT. More...

Typedefs
template<typename T = Real, FFT::Direction D = FFT::Direction::both>
using	C2C = R2C<T, D, true>
	FFT between complex data.

Enumerations
enum struct	Direction { forward , backward , both , none }
enum struct	DomainStrategy { automatic , slab , pencil }
enum class	Boundary : int { periodic , even , odd }
enum struct	Kind {   none , r2c_f , r2c_b , c2c_f ,   c2c_b , r2r_ee_f , r2r_ee_b , r2r_oo_f ,   r2r_oo_b , r2r_eo , r2r_oe }

Functions
Boundary_EnumTraits	amrex_get_enum_traits (Boundary)
constexpr int	FastNumPrimeFactors () noexcept
	Return the default factor count used for selecting fast FFT lengths.
int	nextFastLen (int target, int nfactors=FastNumPrimeFactors())
	Return the smallest fast FFT length greater than or equal to target.

Typedef Documentation

C2C

template<typename T = Real, FFT::Direction D = FFT::Direction::both>

using amrex::FFT::C2C = R2C<T, D, true>

FFT between complex data.

Enumeration Type Documentation

Boundary

enum class amrex::FFT::Boundary : int

strong

Enumerator
periodic
even
odd

Direction

enum struct amrex::FFT::Direction

strong

Enumerator
forward
backward
both
none

DomainStrategy

enum struct amrex::FFT::DomainStrategy

strong

Enumerator
automatic
slab
pencil

Kind

enum struct amrex::FFT::Kind

strong

Enumerator
none
r2c_f
r2c_b
c2c_f
c2c_b
r2r_ee_f
r2r_ee_b
r2r_oo_f
r2r_oo_b
r2r_eo
r2r_oe

Function Documentation

amrex_get_enum_traits()

Boundary_EnumTraits amrex::FFT::amrex_get_enum_traits

(

Boundary

)

FastNumPrimeFactors()

int amrex::FFT::FastNumPrimeFactors ( )

nodiscardconstexprnoexcept

Return the default factor count used for selecting fast FFT lengths.

The default is platform dependent. CUDA currently uses 5; other backends currently use 6. This tuning default may change in the future.

Returns

Default number of prime factors used by FFT::nextFastLen.

nextFastLen()

int amrex::FFT::nextFastLen ( int target, int nfactors = FastNumPrimeFactors() )

inlinenodiscard

Return the smallest fast FFT length greater than or equal to target.

The allowed factors are the first nfactors values from {2, 3, 5, 7, 11, 13}. When nfactors is omitted, FFT::FastNumPrimeFactors() provides a platform-dependent default.

Parameters

target	Minimum requested FFT length. It must be positive.
nfactors	Number of supported prime factors. It must be between 3 and 6.

Returns

A fast FFT length no smaller than target.