autopas::VerletListsCellsHelpers Namespace Reference

Helper functions and type aliases for verlet lists cells. More...

Classes
struct	BaseStepOffsets
	Helper Struct to bundle all information about base step offsets. More...

Typedefs
template<class Particle_T >
using	AllCellsNeighborListsType = std::vector< std::vector< std::pair< Particle_T *, std::vector< Particle_T * > > > >
	Cell wise verlet lists for neighbors from all adjacent cells: For every cell, a vector of pairs.
template<class Particle_T >
using	PairwiseNeighborListsType = std::vector< std::vector< std::vector< std::pair< Particle_T *, std::vector< Particle_T * > > > > >
	Pairwise verlet lists: For every cell a vector, for every neighboring cell a vector of particle-neighborlist pairs.

Enumerations
enum class	VLCBuildType { aosBuild , soaBuild }
	Indicates which build functor should be used for the generation of the neighbor list. More...

Functions
size_t	estimateListLength (size_t numParticles, const std::array< double, 3 > &boxSize, double interactionLength, double correctionFactor)
	Simple heuristic to calculate the average number of particles per verlet list assuming particles are evenly distributed in the domain box.
std::vector< BaseStepOffsets >	buildC08BaseStep (const std::array< int, 3 > &cellsPerDim)
	Builds the list of offsets from the base cell for the c08 base step.
template<class Cells >
size_t	estimateNumLists (size_t baseCellIndex, bool useNewton3, const Cells &cells, const std::vector< BaseStepOffsets > &offsetsC08)
	Function to estimate the number of neighbor lists for one base step.

Detailed Description

Helper functions and type aliases for verlet lists cells.

Typedef Documentation

AllCellsNeighborListsType

template<class Particle_T >

using autopas::VerletListsCellsHelpers::AllCellsNeighborListsType = typedef std::vector<std::vector<std::pair<Particle_T *, std::vector<Particle_T *> >> >

Cell wise verlet lists for neighbors from all adjacent cells: For every cell, a vector of pairs.

Each pair maps a particle to a vector of its neighbors.

Note

From a content view, this is similar to an vector<unstructured_map<Particle_T*, std::vector<Particle *>>>. However since we need to access all keys sequentially during the force computation this is faster, even when the lookup of keys is slower.

Template Parameters

Particle_T

PairwiseNeighborListsType

template<class Particle_T >

using autopas::VerletListsCellsHelpers::PairwiseNeighborListsType = typedef std::vector<std::vector<std::vector<std::pair<Particle_T *, std::vector<Particle_T *> >> >>

Pairwise verlet lists: For every cell a vector, for every neighboring cell a vector of particle-neighborlist pairs.

Each pair maps a particle to a vector of its neighbor particles. Cells<NeighboringCells<Particle,NeighborParticles>>

Template Parameters

Particle_T

Enumeration Type Documentation

VLCBuildType

enum class autopas::VerletListsCellsHelpers::VLCBuildType

strong

Indicates which build functor should be used for the generation of the neighbor list.

To be passed to the generator functors in the neighbor lists.

Function Documentation

buildC08BaseStep()

std::vector< BaseStepOffsets > autopas::VerletListsCellsHelpers::buildC08BaseStep

(

const std::array< int, 3 > &

cellsPerDim

)

Builds the list of offsets from the base cell for the c08 base step.

A offset pair are two cell indices relative to the base cell index that have to interact.

The third tuple entry is an estimation factor on the fraction of particles that will end up needing a neighbor list in the base cell. This depends on the relative position of the two cells: Whether they are the same, or share a face, edge, or corner.

Note

This function is implemented for CSF==1, meaning preallocation weight factors are intended for CSF==1. For CSF > 1 the implementation works but the factors might be suboptimal. For CSF < 1 more factors (and different) are needed if more neighbor cells interact with the base cell.

Parameters

cellsPerDim

Number of cells per dimension including halo.

Returns

Vector of tuples<offset1, offset2, listEstimateFactor>

estimateListLength()

size_t autopas::VerletListsCellsHelpers::estimateListLength	(	size_t	numParticles,
		const std::array< double, 3 > &	boxSize,
		double	interactionLength,
		double	correctionFactor
	)

Simple heuristic to calculate the average number of particles per verlet list assuming particles are evenly distributed in the domain box.

Parameters

numParticles
boxSize	Size of the simulation box.
interactionLength	Cutoff + skin.
correctionFactor	Correction factor multiplied with the result.

Returns

numParticles * (list volume as fraction of box volume) * correctionFactor.

estimateNumLists()

template<class Cells >

size_t autopas::VerletListsCellsHelpers::estimateNumLists	(	size_t	baseCellIndex,
		bool	useNewton3,
		const Cells &	cells,
		const std::vector< BaseStepOffsets > &	offsetsC08
	)

Function to estimate the number of neighbor lists for one base step.

Template Parameters

Cells

Parameters

baseCellIndex	Cell index for which the estimate is made.
useNewton3	Whether or not the traversal that uses the lists employs Newton3.
cells	Reference to the vector of cells.
offsetsC08	Vector of BaseStepOffsets.

Returns

An estimate of the number of lists that will be needed in the base cell.