/*******************************************************************************
* 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.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;
import com.analog.lyric.dimple.solvers.core.parameterizedMessages.GammaParameters;
/**
* Gamma distribution. The variables in the argument list are ordered as follows:
*
* 1) Alpha: Alpha parameter of the Gamma distribution (non-negative)
* 2) Beta: Beta parameter of the Gamma distribution (non-negative)
* 3...) An arbitrary number of real variables
*
* Alpha and Beta parameters may optionally be specified as constants in the constructor.
* In this case, they are not included in the list of arguments.
*
*/
public class Gamma extends UnaryFactorFunction implements IParametricFactorFunction
{
private static final long serialVersionUID = 1L;
protected GammaParameters _parameters;
protected boolean _parametersConstant = false;
protected int _firstDirectedToIndex = 2;
/*--------------
* Construction
*/
private Gamma(GammaParameters parameters, boolean constant)
{
super((String)null);
_parameters = parameters;
_parametersConstant = constant;
_firstDirectedToIndex = constant? 0 : 2;
}
public Gamma()
{
this(new GammaParameters(0.0, 0.0), false);
}
/**
*
* @param parameters
* @since 0.08
*/
public Gamma(GammaParameters parameters)
{
this(parameters, true);
}
public Gamma(double alpha, double beta)
{
this(new GammaParameters(alpha-1,beta));
}
/**
* Construct from specified parameters
* @param parameters the following values are supported
* <ul>
* <li>alpha (default 1.0)
* <li>beta (default 1.0)
* </ul>
* @since 0.07
*/
public Gamma(Map<String,Object> parameters)
{
this((double)getOrDefault(parameters, "alpha", 1.0), (double)getOrDefault(parameters, "beta", 1.0));
}
protected Gamma(Gamma other)
{
super(other);
_parameters = other._parameters.clone();
_firstDirectedToIndex = other._firstDirectedToIndex;
_parametersConstant = other._parametersConstant;
}
@Override
public Gamma clone()
{
return new Gamma(this);
}
/*----------------
* IDatum methods
*/
@Override
public boolean objectEquals(@Nullable Object other)
{
if (this == other)
{
return true;
}
if (other instanceof Gamma)
{
Gamma that = (Gamma)other;
return _parametersConstant == that._parametersConstant &&
_parameters.objectEquals(that._parameters) &&
_firstDirectedToIndex == that._firstDirectedToIndex;
}
return false;
}
/*------------------------
* FactorFunction methods
*/
@Override
public final double evalEnergy(Value[] arguments)
{
int index = 0;
if (!_parametersConstant)
{
double alpha = arguments[index++].getDouble();
if (alpha <= 0)
return Double.POSITIVE_INFINITY;
_parameters.setAlpha(alpha);
double beta = arguments[index++].getDouble();
if (beta <= 0)
return Double.POSITIVE_INFINITY;
_parameters.setBeta(beta);
}
return _parameters.evalNormalizedEnergy(arguments, index);
}
@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("alpha", _parameters.getAlpha());
parameters.put("beta", _parameters.getBeta());
return 2;
}
return 0;
}
@Override
public @Nullable Object getParameter(String parameterName)
{
if (_parametersConstant)
{
switch (parameterName)
{
case "alpha":
return _parameters.getAlpha();
case "beta":
return _parameters.getBeta();
}
}
return null;
}
@Override
public GammaParameters getParameterizedMessage()
{
return _parameters;
}
@Override
public final boolean hasConstantParameters()
{
return _parametersConstant;
}
/*-------------------------
* Factor-specific methods
*/
public final double getAlphaMinusOne()
{
return _parameters.getAlphaMinusOne();
}
public final double getBeta()
{
return _parameters.getBeta();
}
}