/*******************************************************************************
* 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 com.analog.lyric.dimple.exceptions.DimpleException;
import com.analog.lyric.dimple.factorfunctions.core.FactorFunction;
import com.analog.lyric.dimple.model.values.Value;
/**
* Deterministic negation real-joint variables. This is a deterministic directed factor (if smoothing is
* not enabled).
*
* Optional smoothing may be applied, by providing a smoothing value in the
* constructor. If smoothing is enabled, the distribution is smoothed by
* exp(-difference^2/smoothing), where difference is the distance between the
* output value and the deterministic output value for the corresponding inputs.
*
* The variables are ordered as follows in the argument list:
*
* 1) Output (negative of input)
* 2) Input (RealJoint)
*
* @since 0.05
*/
public class RealJointNegate extends FactorFunction
{
protected double _beta = 0;
protected boolean _smoothingSpecified = false;
public RealJointNegate() {this(0);}
public RealJointNegate(double smoothing)
{
super();
if (smoothing > 0)
{
_beta = 1 / smoothing;
_smoothingSpecified = true;
}
}
@Override
public final double evalEnergy(Value[] arguments)
{
// Output variable
final double[] out = arguments[0].getDoubleArray();
final int dimension = out.length;
// Input variable
final double[] in = arguments[1].getDoubleArray();
if (dimension != in.length) throw new DimpleException("Argument variables must all have the same dimension");
if (_smoothingSpecified)
{
double potential = 0;
for (int d = 0; d < dimension; d++)
{
final double diff = in[d] + out[d];
potential += diff*diff;
}
return potential*_beta;
}
else
{
boolean equal = true;
for (int d = 0; d < dimension; d++)
if (-in[d] != out[d])
equal = false;
return (equal) ? 0 : Double.POSITIVE_INFINITY;
}
}
@Override
public final boolean isDirected() {return true;}
@Override
public final int[] getDirectedToIndices() {return new int[]{0};}
@Override
public final boolean isDeterministicDirected() {return !_smoothingSpecified;}
@Override
public final void evalDeterministic(Value[] arguments)
{
// Output variable
final double[] out = arguments[0].getDoubleArray();
final int dimension = out.length;
// Input variable
final double[] in = arguments[1].getDoubleArray();
if (dimension != in.length) throw new DimpleException("Argument variables must all have the same dimension");
for (int d = 0; d < dimension; d++)
out[d] = -in[d];
}
}