Package etomica.math.numerical

Class CalcGradientDifferentiable

java.lang.Object

etomica.math.numerical.CalcGradientDifferentiable

All Implemented Interfaces:

FunctionMultiDimensional, FunctionMultiDimensionalDifferentiable

public class CalcGradientDifferentiable
extends java.lang.Object
implements FunctionMultiDimensionalDifferentiable

Uses finite difference methods to determine the second order differential of the potential (i.e. dF/dx). Part of a larger scheme, a user may employ this to fill a two-dimensional array of changes in molecule A's Force with respect to the movement of other molecules.

Field Summary

Fields

Modifier and Type	Field	Description
IteratorDirective	allAtoms
Box	box
double	forceConstant
PotentialMaster	potentialMaster

Constructor Summary

Constructors

Constructor	Description
CalcGradientDifferentiable(Box aBox, PotentialMaster aPotentialMaster, IMoleculeList movableSet, Space _space)

Method Summary

Modifier and Type	Method	Description
double	df(int[] d, double[] position)	Returns the derivative indicated by the array d evaluated at the given point x.
double[]	df2(int[] d, double[] position)	Uses the potential's force calculation at different displacements of a molecule in X, Y and Z to determine the second derivative of the potential.
double	f(double[] position)
int	getDimension()	The dimension of the space of independent variables.
void	setComponent(int aGradDcomponent)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

box

public Box box

potentialMaster

public PotentialMaster potentialMaster

forceConstant

public double forceConstant

allAtoms

public IteratorDirective allAtoms

Constructor Detail

CalcGradientDifferentiable

public CalcGradientDifferentiable(Box aBox,
                                  PotentialMaster aPotentialMaster,
                                  IMoleculeList movableSet,
                                  Space _space)

Method Detail

setComponent

public void setComponent(int aGradDcomponent)

f

public double f(double[] position)

Specified by:

f in interface FunctionMultiDimensional

df

public double df(int[] d,
                 double[] position)

Description copied from interface: FunctionMultiDimensionalDifferentiable

Returns the derivative indicated by the array d evaluated at the given point x. The array d should be the same length as x. Each entry of d specifies the order of the derivative taken with respect to the corresponding variable in x. For example, for a function on a 2-dimensional space, d = {2,0}, indicates d2f/dx[0]^2, while d = {1,1}, indicates d2f/dx[0]dx[1]; d = {2,1} indicates d3f/dx[0]^2dx[1]; etc.

Specified by:

df in interface FunctionMultiDimensionalDifferentiable

df2

public double[] df2(int[] d,
                    double[] position)

Uses the potential's force calculation at different displacements of a molecule in X, Y and Z to determine the second derivative of the potential. Here, H (our displacement distance) is equal to 0.0001.

Parameters:

d - A one-dimensional array describing what column of our larger, global dF/dx array we are working with.

position - A one dimensional array of doubles describing the molecules positions.

Returns:

getDimension

public int getDimension()

Description copied from interface: FunctionMultiDimensional

The dimension of the space of independent variables. The length of the array passed to the f should be equal to this quantity.

Specified by:

getDimension in interface FunctionMultiDimensional