/*******************************************************************************
* Copyright 2013 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.solvers.gibbs.samplers.conjugate;
import static com.analog.lyric.dimple.environment.DimpleEnvironment.*;
import static java.util.Objects.*;
import java.util.List;
import org.eclipse.jdt.annotation.Nullable;
import com.analog.lyric.dimple.data.IDatum;
import com.analog.lyric.dimple.factorfunctions.Gamma;
import com.analog.lyric.dimple.factorfunctions.core.IUnaryFactorFunction;
import com.analog.lyric.dimple.model.domains.RealDomain;
import com.analog.lyric.dimple.solvers.core.parameterizedMessages.GammaParameters;
import com.analog.lyric.dimple.solvers.core.parameterizedMessages.IParameterizedMessage;
import com.analog.lyric.dimple.solvers.interfaces.ISolverEdgeState;
public class GammaSampler implements IRealConjugateSampler
{
private final GammaParameters _parameters = new GammaParameters();
@Override
public final double nextSample(ISolverEdgeState[] edges, List<? extends IDatum> inputs)
{
aggregateParameters(_parameters, edges, inputs);
return nextSample(_parameters);
}
@Override
public final void aggregateParameters(IParameterizedMessage aggregateParameters, ISolverEdgeState[] edges,
List<? extends IDatum> inputs)
{
GammaParameters parameters = (GammaParameters)aggregateParameters;
parameters.setNull();
for (IDatum input : inputs)
{
GammaParameters gammaInput;
if (input instanceof GammaParameters)
{
gammaInput = (GammaParameters)input;
}
else if (input instanceof Gamma)
{
gammaInput = ((Gamma)input).getParameterizedMessage();
}
else
continue; // should be impossible
parameters.addFrom(gammaInput);
}
final int numEdges = edges.length;
for (int i = 0; i < numEdges; i++)
{
// The message from each neighboring factor is an array with elements (alpha, beta)
GammaParameters message = requireNonNull((GammaParameters)edges[i].getFactorToVarMsg());
parameters.addFrom(message);
}
}
public final double nextSample(GammaParameters parameters)
{
double alphaMinusOne = parameters.getAlphaMinusOne();
double beta = parameters.getBeta();
return activeRandom().nextGamma(alphaMinusOne + 1, beta);
}
@Override
public IParameterizedMessage createParameterMessage()
{
return new GammaParameters();
}
// A static factory that creates a sampler of this type
public static final IRealConjugateSamplerFactory factory = new IRealConjugateSamplerFactory()
{
@Override
public IRealConjugateSampler create() {return new GammaSampler();}
@Override
public boolean isCompatible(@Nullable IUnaryFactorFunction factorFunction)
{
if (factorFunction == null)
return true;
else if (factorFunction instanceof Gamma || factorFunction instanceof GammaParameters)
return true;
else
return false;
}
@Override
public boolean isCompatible(RealDomain domain)
{
return (domain.getLowerBound() <= 0) && (domain.getUpperBound() == Double.POSITIVE_INFINITY);
}
};
}