import PersistenceConstraint from 'Artistoo/src/hamiltonian/PersistenceConstraint.js'

public class | source

PersistenceConstraint

Extends:

Constraint → SoftConstraint → PersistenceConstraint

This is a constraint in which each cell has a preferred direction of migration. This direction is only dependent on the cell, not on the specific pixel of a cell.

This constraint works with torus as long as the field size is large enough.

Test:

Constructor Summary

Public Constructor
public	constructor(conf: object) The constructor of the PersistenceConstraint requires a conf object with parameters.

Member Summary

Public Members
public set	CPM(C: CPM) Set the CPM attached to this constraint.
public	cellcentroidlists: CellObject Cache centroids over the previous conf.DELTA_T MCS to determine directions.
public	celldirections: CellObject Target direction of movement of each cell.

Method Summary

Public Methods
public	confChecker() This method checks that all required parameters are present in the object supplied to the constructor, and that they are of the right format.
public	deltaH(sourcei: IndexCoordinate, targeti: IndexCoordinate, src_type: CellId, tgt_type: CellId): number Method to compute the Hamiltonian for this constraint.
public	postMCSListener() After each MCS, update the target direction of each cell based on its actual direction over the last {conf.DELTA_T[cellkind]} steps, and some angular noise depending on {conf.PERSIST[cellkind]}.
public	randDir(n: number): number[] This function samples a random direction vector with length 1
public	setDirection(t: CellId, dx: number[]) Change the target direction of a cell to a given vector.

Private Methods
private	normalize(a: number[]): number[] Normalize a vector a by its length.
private	sampleNorm(mu: number, sigma: number): number this function samples a random number from a normal distribution

Inherited Summary

From class Constraint
public get abstract	CONSTRAINT_TYPE This method is actually implemented in the subclass.
public set	CPM(C: CPM) This function attaches the relevant CPM to this constraint, so that information about this cpm can be requested from the constraint.
public get	parameters: object: * Get the parameters of this constraint from the conf object.
public	C: CPM CPM on which this constraint acts.
public	conf: object Configuration object for this constraint.
public abstract	cellParameter(param: string, cid: CellId): any Get a cellid or cellkind-specific parameter for a constraint.
public abstract	confChecker() The optional confChecker method should verify that all the required conf parameters are actually present in the conf object and have the right format.
public	paramOfCell(param: string, cid: CellId): any Get a cellId specific parameter, only used if CPMEvol is used: looks whether the requested parameter is overwritten in an @object Cell and otherwise returns @function paramOfKind
public	paramOfKind(param: string, cid: CellId): any Returns a cellKind specfic variable: Assumes that the parameter is indexable by cellkind.

From class SoftConstraint
public get	CONSTRAINT_TYPE: string: string Let the CPM know that this is a soft constraint, so return 'soft'.
public abstract	deltaH(src_i: IndexCoordinate, tgt_i: IndexCoordinate, src_type: CellId, tgt_type: CellId): number Soft constraints must have a deltaH method to compute the Hamiltonian.

Public Constructors

public constructor(conf: object) source

The constructor of the PersistenceConstraint requires a conf object with parameters.

Override:

Constraint#constructor

Params:

Name	Type	Attribute	Description
conf	object		parameter object for this constraint
conf.LAMBDA_DIR	PerKindNonNegative		strength of the persistenceconstraint per cellkind.
conf.DELTA_T	PerKindNonNegative	optional default: [10,10,...]	the number of MCS over which the current direction is determined. Eg if DELTA_T = 10 for a cellkind, then its current direction is given by the vector from its centroid 10 MCS ago to its centroid now.
conf.PERSIST	PerKindProb		persistence per cellkind. If this is 1, its new target direction is exactly equal to its current direction. If it is lower than 1, angular noise is added accordingly.

Public Members

public set CPM(C: CPM) source

Set the CPM attached to this constraint.

Override:

Constraint#CPM

public cellcentroidlists: CellObject source

Cache centroids over the previous conf.DELTA_T MCS to determine directions.

public celldirections: CellObject source

Target direction of movement of each cell.

Public Methods

public confChecker() source

This method checks that all required parameters are present in the object supplied to the constructor, and that they are of the right format. It throws an error when this is not the case.

Override:

Constraint#confChecker

public deltaH(sourcei: IndexCoordinate, targeti: IndexCoordinate, src_type: CellId, tgt_type: CellId): number source

Method to compute the Hamiltonian for this constraint.

Override:

SoftConstraint#deltaH

Params:

Name	Type	Attribute	Description
sourcei	IndexCoordinate		coordinate of the source pixel that tries to copy.
targeti	IndexCoordinate		coordinate of the target pixel the source is trying to copy into.
src_type	CellId		cellid of the source pixel.
tgt_type	CellId		cellid of the target pixel. This argument is not used by this method, but is supplied for consistency with other SoftConstraints. The CPM will always call this method supplying the tgt_type as fourth argument.

Return:

number

the change in Hamiltonian for this copy attempt and this constraint.

public postMCSListener() source

After each MCS, update the target direction of each cell based on its actual direction over the last {conf.DELTA_T[cellkind]} steps, and some angular noise depending on {conf.PERSIST[cellkind]}.

Listen:

timeStep

because when the CPM has finished an MCS, cells have new centroids and their direction must be updated.

public randDir(n: number): number[] source

This function samples a random direction vector with length 1

Params:

Name	Type	Attribute	Description
n	number	optional default: 3	number of dimensions of the space to make the vector in.

Return:

number[]

a normalized direction vector.

public setDirection(t: CellId, dx: number[]) source

Change the target direction of a cell to a given vector.

Params:

Name	Type	Attribute	Description
t	CellId		the cellid of the cell to change the direction of.
dx	number[]		the new direction this cell should get.

Private Methods

private normalize(a: number[]): number[] source

Normalize a vector a by its length.

Params:

Name	Type	Attribute	Description
a	number[]		vector to normalize.

Return:

number[]

normalized version of this vector.

private sampleNorm(mu: number, sigma: number): number source

this function samples a random number from a normal distribution

Params:

Name	Type	Attribute	Description
mu	number	optional default: 0	mean of the normal distribution.
sigma	number	optional default: 1	SD of the normal distribution.

Return:

number

the random number generated.