Miscellaneous helpers

Collaboration diagram for Miscellaneous helpers:

Enumerations
enum class	heffte::direction { heffte::forward , heffte::backward }
	Indicates the direction of the FFT (internal use only). More...

Functions
template<typename index >
std::ostream &	heffte::operator<< (std::ostream &os, box3d< index > const box)
	Debugging info, writes out the box to a stream.
int	heffte::get_area (std::array< int, 2 > const &dims)
	Get the surface area of a processor grid. More...
std::array< int, 2 >	heffte::make_procgrid (int const num_procs)
	Factorize the MPI ranks into a 2D grid. More...
template<typename index >
std::array< int, 3 >	heffte::make_procgrid2d (box3d< index > const world, int direction_1d, std::array< int, 2 > const candidate_grid)
	Factorize the MPI ranks into a 2D grid with specific constraints. More...
template<class T , class U = T>
T	heffte::c11_exchange (T &obj, U &&new_value)
	Replace with the C++ 2014 std::exchange later.
template<typename some_class >
int	heffte::get_last_active (std::array< std::unique_ptr< some_class >, 4 > const &shaper)
	Return the index of the last active (non-null) unique_ptr. More...
template<typename some_class >
int	heffte::count_active (std::array< std::unique_ptr< some_class >, 4 > const &shaper)
	Return the number of active (non-null) unique_ptr.
template<typename some_class >
size_t	heffte::get_max_box_size (std::array< some_class, 3 > const &executors)
	Returns the max of the box_size() for each of the executors.
template<typename some_class >
size_t	heffte::get_max_box_size_r2c (std::array< some_class, 3 > const &executors)
	Returns the max of the box_size() for each of the executors.
template<typename some_class >
size_t	heffte::get_max_work_size (std::array< some_class, 3 > const &executors)
	Returns the max of the workspace_size() for each of the executors.
template<typename some_class_r2c , typename some_class >
size_t	heffte::get_max_work_size (some_class_r2c const &executors_r2c, std::array< some_class, 2 > const &executors)
	Returns the max of the workspace_size() for each of the executors.

Detailed Description

Simple helper templates.

Enumeration Type Documentation

direction

enum heffte::direction

strong

Indicates the direction of the FFT (internal use only).

Enumerator
forward	Forward DFT transform.
backward	Inverse DFT transform.

Function Documentation

get_area()

int heffte::get_area ( std::array< int, 2 > const &  dims )

inline

Get the surface area of a processor grid.

For a three dimensional grid with size dims[0] by dims[1] by 1, returns the surface area. Useful for optimizing average communication cost.

make_procgrid()

std::array<int, 2> heffte::make_procgrid ( int const  num_procs )

inline

Factorize the MPI ranks into a 2D grid.

Considers all possible factorizations of the total number of processors and select the one with the lowest area which heuristically reduces the number of ranks that need to communicate in each of the all-to-all operations.

Parameters

num_procs

is the total number of processors to factorize

Returns

the two dimensions of the grid

make_procgrid2d()

template<typename index >

std::array<int, 3> heffte::make_procgrid2d ( box3d< index > const  world, int  direction_1d, std::array< int, 2 > const  candidate_grid  )

inline

Factorize the MPI ranks into a 2D grid with specific constraints.

The constraints satisfied by the grid will be as follow:

• result[i] <= world.size[i], i.e., we don't use more processors than there are indexes
• result[direction_1d] == 1, i.e., the grid is one-dimensional in the given direction_1d
• the product of result[i] will be equal to the product of candidate_grid[0] * candidate_grid[1]
• if possible, the candidate_grid factorization will be used with the implicit assumption that it will be best or optimal except when the fist constraint is violated

get_last_active()

template<typename some_class >

int heffte::get_last_active

(

std::array< std::unique_ptr< some_class >, 4 > const &

shaper

)

Return the index of the last active (non-null) unique_ptr.

The method returns -1 if all shapers are null.