/*******************************************************************************
* Copyright 2012-2015 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.minsum;
public class MessageConverter
{
public static final double maxPotential = 1000; // Clip the potential (-log(P)) to this value
public static double clipEnergy(double energy)
{
return Math.min(energy, maxPotential);
}
public static void clipEnergies(double[] energies)
{
for (int i = energies.length; --i>=0;)
if (energies[i] > maxPotential)
energies[i] = maxPotential;
}
public static double[] fromProb(double[] in)
{
int numValue = in.length;
double[] out = new double[numValue];
for (int i = 0; i < numValue; i++)
out[i] = Math.min(-Math.log(in[i]),maxPotential);
return out;
}
public static double[] toProb(double[] in)
{
int numValue = in.length;
double[] out = new double[numValue];
double minPotential = Double.POSITIVE_INFINITY;
double sum = 0;
for (int i = 0; i < numValue; i++)
if (in[i] < minPotential) minPotential = in[i];
for (int i = 0; i < numValue; i++)
{
out[i] = Math.exp(-(in[i] - minPotential));
sum += out[i];
}
for (int i = 0; i < numValue; i++) out[i] /= sum; // Normalize to probability values
return out;
}
public static double[] initialValue(int numValue)
{
return new double[numValue];
}
}