/*******************************************************************************
* Copyright 2012 Analog Devices, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
********************************************************************************/
package com.analog.lyric.dimple.factorfunctions;
import java.util.Map;
import org.eclipse.jdt.annotation.Nullable;
import com.analog.lyric.dimple.exceptions.DimpleException;
import com.analog.lyric.dimple.factorfunctions.core.FactorFunctionUtilities;
import com.analog.lyric.dimple.factorfunctions.core.IParametricFactorFunction;
import com.analog.lyric.dimple.factorfunctions.core.UnaryFactorFunction;
import com.analog.lyric.dimple.model.values.Value;
/**
* Rayleigh distribution.
* <p>
* The variables in the argument list are ordered as follows:
* <ol>
* <li>Sigma parameter (non-negative)
* <li>An arbitrary number of real variables
* </ol>
* The sigma parameter may optionally be specified as constant in the constructor.
* In this case, it is not included in the list of arguments.
*/
public class Rayleigh extends UnaryFactorFunction implements IParametricFactorFunction
{
private static final long serialVersionUID = 1L;
protected double _sigma;
protected double _inverseSigmaSquared;
protected double _halfInverseSigmaSquared;
protected boolean _parametersConstant = false;
protected int _firstDirectedToIndex = 1;
/*--------------
* Construction
*/
public Rayleigh() {super((String)null);}
public Rayleigh(double sigma)
{
this();
_sigma = sigma;
_inverseSigmaSquared = 1/(_sigma*_sigma);
_halfInverseSigmaSquared = _inverseSigmaSquared * 0.5;
_parametersConstant = true;
_firstDirectedToIndex = 0;
if (_sigma < 0) throw new DimpleException("Negative sigma value. This must be a non-negative value.");
}
/**
* Constructs Rayleigh distribution with fixed sigma parameter.
* @param parameters If this contains an entry under the key "sigma", that will be used for the
* corresponding parameter, otherwise it will default to 1.0.
* @since 0.07
*/
public Rayleigh(Map<String,Object> parameters)
{
this((double)getOrDefault(parameters, "sigma", 1.0));
}
protected Rayleigh(Rayleigh other)
{
super(other);
_sigma = other._sigma;
_inverseSigmaSquared = other._inverseSigmaSquared;
_halfInverseSigmaSquared = other._halfInverseSigmaSquared;
_parametersConstant = other._parametersConstant;
_firstDirectedToIndex = other._firstDirectedToIndex;
}
@Override
public Rayleigh clone()
{
return new Rayleigh(this);
}
/*----------------
* IDatum methods
*/
@Override
public boolean objectEquals(@Nullable Object other)
{
if (this == other)
{
return true;
}
if (other instanceof Rayleigh)
{
Rayleigh that = (Rayleigh)other;
return _parametersConstant == that._parametersConstant &&
_sigma == that._sigma &&
_firstDirectedToIndex == that._firstDirectedToIndex; }
return false;
}
/*------------------------
* FactorFunction methods
*/
@Override
public final double evalEnergy(Value[] arguments)
{
int index = 0;
if (!_parametersConstant)
{
_sigma = arguments[index++].getDouble(); // First variable is sigma
_inverseSigmaSquared = 1/(_sigma*_sigma);
_halfInverseSigmaSquared = _inverseSigmaSquared * 0.5;
if (_sigma < 0) return Double.POSITIVE_INFINITY;
}
final int length = arguments.length;
double sum = 0;
for (; index < length; index++)
{
final double x = arguments[index].getDouble(); // Remaining inputs are Rayleigh variables
if (x < 0)
return Double.POSITIVE_INFINITY;
else
sum += x*x*_halfInverseSigmaSquared - Math.log(x*_inverseSigmaSquared);
}
return sum;
}
@Override
public final boolean isDirected() {return true;}
@Override
public final int[] getDirectedToIndices(int numEdges)
{
// All edges except the parameter edges (if present) are directed-to edges
return FactorFunctionUtilities.getListOfIndices(_firstDirectedToIndex, numEdges-1);
}
/*-----------------------------------
* IParametricFactorFunction methods
*/
@Override
public int copyParametersInto(Map<String, Object> parameters)
{
if (_parametersConstant)
{
parameters.put("sigma", _sigma);
return 1;
}
return 0;
}
@Override
public @Nullable Object getParameter(String parameterName)
{
if (_parametersConstant)
{
switch (parameterName)
{
case "sigma":
return _sigma;
}
}
return null;
}
@Override
public boolean hasConstantParameters()
{
return _parametersConstant;
}
}