Class for create a galaxy cellular automata model. More...

#include <galaxydatatypes.h>

Public Member Functions
	Galaxy ()
	Construct a new Galaxy object using the following default parameters: min_mass = 1; max_mass = 100; density = 0.3; boundary_radius = 3; axis1_dim = 1; axis2_dim = 6; axis3_dim = 6; boundary_radius = 1;. More...

	Galaxy (double time_step, int min_mass, int max_mass, double density, int boundary_radius, int axis1_dim, int axis2_dim, int axis3_dim)
	Create a Galaxy model instance using the provided values. More...

	~Galaxy ()=default
	Destroy the Galaxy object. More...

int	init_galaxy ()
	Sets up the galaxy CA instance. More...

int	simulation (int steps)
	Runs the simulation for the specified amount of steps. More...

Static Public Member Functions
static void	galaxy_formation_rule (int cell_index, const int index_size, GalaxyCell neighborhood_cells, const int neighborhood_size, GalaxyCell &new_cell_state)
	Custom CA rule for simulating the motion of star systems. More...

static void	set_new_position (int *cell_index, GalaxyCell &new_cell_state, const std::vector< double > &displacement_vector)
	Set the new_cell_state's new position. More...

static bool	did_galaxies_collide (int *cell_index, const std::vector< int > &offset_index, GalaxyCell &new_cell_state)
	Determines if the new_cell_state collides with a cell at the current position: cell_index + offset_index. More...

static void	update_velocity_after_collision (GalaxyCell &new_cell, GalaxyCell collied_cell)
	compute the velocity after an inelastic collision https://www.plasmaphysics.org.uk/collision3d.htm More...

static GalaxyCell &	get_cell_state (int *cell_index, const std::vector< int > &offset_index)
	Get the cell state object at position cell_index + offset_index from the CellularAutomata instance. More...

static std::vector< int >	get_periodic_vector (int *cell_index, const std::vector< int > &offset_index)
	Get the periodic vector. More...

static int	round_int (double dbl)
	Rounds a double to an int. More...

static std::vector< double >	compute_gravitational_force (const GalaxyCell &cell_of_interest, const GalaxyCell &neighbor_cell, const std::vector< int > &neighbor_index)
	Computes the force between cell of interest and neighbor_index Note: cell of interest is at (0, 0, 0) More...

static std::vector< double >	compute_accel (const std::vector< double > &total_force, double mass)
	Computes the acceleration vector A = F/M. More...

static std::vector< double >	compute_velocity (const std::vector< double > &accel, const GalaxyCell &cell_of_interest, double time_step)
	Computes the velocity vector. More...

static std::vector< double >	compute_displacement (const std::vector< double > &velocity, const GalaxyCell &cell_of_interest, double time_step)
	Computes the displacement vector. More...

static double	compute_vector_norm (const std::vector< int > &vector)
	Computes the norm of a vector. More...

static std::vector< double >	compute_vector_difference (const std::vector< double > &vec1, const std::vector< double > &vec2)
	Computes the difference in vector for determining the direction and magnitude of the force vector. More...

Public Attributes
int	min_mass
	minimum cell mass (int required for rand)

int	max_mass
	maximum cell mass (int required for rand)

double	density
	density of galaxy

int	boundary_radius
	cutoff radius above which forces are not considered

int	axis1_dim
	cellular automata axis1 dimension

int	axis2_dim
	cellular automata axis2 dimension

int	axis3_dim
	cellular automata axis3 dimension

Static Public Attributes
static double	time_step
	time_step for computing forces during each simulation step

static CellularAutomata< GalaxyCell >	CA
	the CA the simulation utilizes to model the formation of a galaxy

Detailed Description

Class for create a galaxy cellular automata model.

Only one instance should be created since the CellularAutomata instance is static and will be shared among all instances. CellularAutomata accepts a free function and not a member function thus galaxy_formation_rule needs to be static. In order for galaxy_formation_rule to access the CellularAutomata and other class variable, they need to be static.

Constructor & Destructor Documentation

◆ Galaxy() [1/2]

Galaxy::Galaxy ( )

Construct a new Galaxy object using the following default parameters:
min_mass = 1;
max_mass = 100;
density = 0.3;
boundary_radius = 3;
axis1_dim = 1;
axis2_dim = 6;
axis3_dim = 6;
boundary_radius = 1;.

◆ Galaxy() [2/2]

Galaxy::Galaxy	(	double	time_step,
		int	min_mass,
		int	max_mass,
		double	density,
		int	boundary_radius,
		int	axis1_dim,
		int	axis2_dim,
		int	axis3_dim
	)

Create a Galaxy model instance using the provided values.

If given values are invalid then the default values are used.

Parameters

time_step	simulation time step for computing forces and physical quantities
min_mass	minimum cell mass
max_mass	maximum cell mass
density	density of occupied cell states
boundary_radius	cutoff radius above which forces are not considered
axis1_dim	cellular automata axis1 dimension
axis2_dim	cellular automata axis2 dimension
axis3_dim	cellular automata axis3 dimension

◆ ~Galaxy()

Galaxy::~Galaxy ( )

default

Destroy the Galaxy object.

Member Function Documentation

◆ compute_accel()

static std::vector< double > Galaxy::compute_accel	(	const std::vector< double > &	total_force,
		double	mass
	)

static

Computes the acceleration vector A = F/M.

Parameters

total_force	Sum of all forces in component form
mass	cell of interet's mass

Returns: std::vector<double>

◆ compute_displacement()

static std::vector< double > Galaxy::compute_displacement	(	const std::vector< double > &	velocity,
		const GalaxyCell &	cell_of_interest,
		double	time_step
	)

static

Computes the displacement vector.

D = 1/2 * (velocity_i + velocity_f) * time_step

Parameters

velocity	current step velocity
cell_of_interest	contains initial velocity
time_step	simulation time step

Returns: std::vector<double>

◆ compute_gravitational_force()

static std::vector< double > Galaxy::compute_gravitational_force	(	const GalaxyCell &	cell_of_interest,
		const GalaxyCell &	neighbor_cell,
		const std::vector< int > &	neighbor_index
	)

static

Computes the force between cell of interest and neighbor_index Note: cell of interest is at (0, 0, 0)

F = - m_1 * m_2 / | r_12 | * r_hat
r_hat = r_12 / | r_12 |

Parameters

cell_of_interest
neighbor_cell
neighbor_index

Returns: std::vector<double>

◆ compute_vector_difference()

static std::vector< double > Galaxy::compute_vector_difference	(	const std::vector< double > &	vec1,
		const std::vector< double > &	vec2
	)

static

Computes the difference in vector for determining the direction and magnitude of the force vector.

Parameters

vec1	Initial vector
vec2	Final vector

Returns: std::vector<double>

◆ compute_vector_norm()

static double Galaxy::compute_vector_norm ( const std::vector< int > & vector )

static

Computes the norm of a vector.

Used by compute_gravitational_force.

Parameters

vector

Returns: double

◆ compute_velocity()

static std::vector< double > Galaxy::compute_velocity	(	const std::vector< double > &	accel,
		const GalaxyCell &	cell_of_interest,
		double	time_step
	)

static

Computes the velocity vector.

V = velocity_i + acceleration_i * time_step

Parameters

accel	current step acceleration
cell_of_interest	contains initial velocity
time_step	simulation time step

Returns: std::vector<double>

◆ did_galaxies_collide()

static bool Galaxy::did_galaxies_collide	(	int *	cell_index,
		const std::vector< int > &	offset_index,
		GalaxyCell &	new_cell_state
	)

static

Determines if the new_cell_state collides with a cell at the current position: cell_index + offset_index.

If there is a collision then we set the new_cell_state index to the current position. And also increases the cell state by one to represent the number of collision. The mass and velocity properties are also updated using the laws of physics. Else return false.

Parameters

cell_index	new_cell_state position
offset_index	keep track of path the cell takes
new_cell_state	cell of interests

Returns: true : collision occurred; false : collision didn't occur

◆ galaxy_formation_rule()

static void Galaxy::galaxy_formation_rule	(	int *	cell_index,
		const int	index_size,
		GalaxyCell *	neighborhood_cells,
		const int	neighborhood_size,
		GalaxyCell &	new_cell_state
	)

static

Custom CA rule for simulating the motion of star systems.

Parameters

cell_index	new_cell_state position
index_size	size of cell_index
neighborhood_cells	array of neighboring cells for computing gravitational force
neighborhood_size	size of neighborhood_cells array
new_cell_state	reference to cell state that will be inserted into next state

◆ get_cell_state()

static GalaxyCell & Galaxy::get_cell_state	(	int *	cell_index,
		const std::vector< int > &	offset_index
	)

static

Get the cell state object at position cell_index + offset_index from the CellularAutomata instance.

Parameters

cell_index	current new_cell_state position
offset_index	used to compute the neighboring cell position

Returns: const GalaxyCell&

◆ get_periodic_vector()

static std::vector< int > Galaxy::get_periodic_vector	(	int *	cell_index,
		const std::vector< int > &	offset_index
	)

static

Get the periodic vector.

Parameters

cell_index	current new_cell_state position
offset_index	used to compute the neighboring cell position

Returns: std::vector<int>

◆ init_galaxy()

int Galaxy::init_galaxy ( )

Sets up the galaxy CA instance.

This can be called multiple times if the user wants to restart the simulation using different parameters.

Returns: int - error code
Error codes returned by CellularAutomata instance
0: no error

◆ round_int()

static int Galaxy::round_int ( double dbl )

static

Rounds a double to an int.

Parameters

dbl

Returns: int

◆ set_new_position()

static void Galaxy::set_new_position	(	int *	cell_index,
		GalaxyCell &	new_cell_state,
		const std::vector< double > &	displacement_vector
	)

static

Set the new_cell_state's new position.

This function uses the Bresenham's line algorithm for computing the path from cell_index to cell_index + displacement_vector. This method accounts for the possibility that cells might collied.

Public domain algorithm and open source 3d implementation reference: https://antofthy.gitlab.io/info/graphics/bresenham.procs

Parameters

cell_index	new_cell_state position
new_cell_state	cell that contains mass and velocity
displacement_vector	vector to the new desired position

◆ simulation()

int Galaxy::simulation ( int steps )

Runs the simulation for the specified amount of steps.

Parameters

steps

Returns: int - error code
Error codes returned by CellularAutomata instance
0: no error

◆ update_velocity_after_collision()

static void Galaxy::update_velocity_after_collision	(	GalaxyCell &	new_cell,
		GalaxyCell	collied_cell
	)

static

compute the velocity after an inelastic collision https://www.plasmaphysics.org.uk/collision3d.htm

Parameters

new_cell
collied_cell

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

Include/galaxydatatypes.h

Public Member Functions

Static Public Member Functions

Public Attributes

Static Public Attributes

Detailed Description

Constructor & Destructor Documentation

◆ Galaxy() [1/2]

◆ Galaxy() [2/2]

◆ ~Galaxy()

Member Function Documentation

◆ compute_accel()

◆ compute_displacement()

◆ compute_gravitational_force()

◆ compute_vector_difference()

◆ compute_vector_norm()

◆ compute_velocity()

◆ did_galaxies_collide()

◆ galaxy_formation_rule()

◆ get_cell_state()

◆ get_periodic_vector()

◆ init_galaxy()

◆ round_int()

◆ set_new_position()

◆ simulation()

◆ update_velocity_after_collision()