Extremely Simple Neighbor Particle Search Tree

header-only C++ library.
Periodic boundary is supported.
Test (Demo) is shown in test_neighbor_particle_search_tree.cpp

Instalation

git clone https://github.com/StaticTaku/neighbor_particle_search_tree.git

Usage

Create an object, resize, copy particle positions, update tree, then you can find neighbor particles near any points!
If positions of particles change, then you need to resizse (if number of particles changes), copy particle positions that has changed its positions, update tree, then you can find neighbor particles near any points!

Example

    Tree::NeighborParticleSearchTree tree(DIM, reserved_size); //reserved_size is number of particles allocated inside tree in advance
    tree.Resize(num_of_particles); //change actual number of particles to be searched for. Note that num_of_particles <=  reserved_size.
    for(int i = 0;i<num_of_particles;++i) //Arrange particles in a cube diagonal. The size of cube: size_x, size_y, size_z = [0,100]
        for(int dim = 0;dim<DIM;++dim)
            tree.CopyPos(pos[i][dim], i, dim); //copy pos[i][dim] to ith_particle[dim] inside the tree 
        
    tree.UpdateTree(); //construct tree. Needs to be called after update particle positions
    tree.FindNeighborParticle(point_of_search, search_radius, interaction_list); //Store the index of the particle in the region of search_radius from point_of_search into interaction_list

Search Option

GATHER (Default)

Search radius is finite.
Particles within a radius search_radius centered on point_of_search are registered as neighboring particles in interaction_list.

tree.FindNeighborParticle(point_of_search, search_radius, interaction_list);

tree.FindNeighborParticleWithPeriodicBoundary(point_of_search, search_radius, periodic_boundary_length, interaction_list);

or

tree.FindNeighborParticle<Tree::SearchMode::GATHER>(point_of_search, search_radius, interaction_list);

tree.FindNeighborParticle<Tree::SearchMode::GATHER>(point_of_search, search_radius, periodic_boundary_length, interaction_list);

SYMMETRY

Search radius is finite.
Need to set search radius of all particles search_radius_list before tree.UpdateTree().

for(int i = 0;i<num_of_particles;++i)
    tree.CopySearchRadius(search_radius_list[i], i);

1. Particles within a radius search_radius centered on point_of_search and
2. Any particles j that covers the position point_of_search within a radius search_radius_list[j] centered on position[j]

are registered as neighboring particles in interaction_list.

tree.FindNeighborParticle<Tree::SearchMode::SYMMETRY>(point_of_search, search_radius, interaction_list);

tree.FindNeighborParticleWithPeriodicBoundary<Tree::SearchMode::SYMMETRY>(point_of_search, search_radius, periodic_boundary_length, interaction_list);

Macro

TREE_DEBUG

Print debug info.

how to run test (or demo)

g++ -std=c++17 -O3 test_neighbor_particle_search_tree.cpp && ./a.out