/*
* DeltaExchangeOperator.java
*
* Copyright (c) 2002-2015 Alexei Drummond, Andrew Rambaut and Marc Suchard
*
* This file is part of BEAST.
* See the NOTICE file distributed with this work for additional
* information regarding copyright ownership and licensing.
*
* BEAST is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* BEAST is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with BEAST; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301 USA
*/
package dr.inference.operators;
import dr.inference.model.Bounds;
import dr.inference.model.Parameter;
import dr.math.MathUtils;
/**
* A generic operator for use with a sum-constrained (possibly weighted) vector parameter.
*
* @author Alexei Drummond
* @author Andrew Rambaut
* @version $Id: DeltaExchangeOperator.java,v 1.18 2005/06/14 10:40:34 rambaut Exp $
*/
public class DeltaExchangeOperator extends AbstractCoercableOperator {
public DeltaExchangeOperator(Parameter parameter, double delta) {
super(CoercionMode.COERCION_ON);
this.parameter = parameter;
this.delta = delta;
setWeight(1.0);
this.isIntegerOperator = false;
parameterWeights = new int[parameter.getDimension()];
for (int i = 0; i < parameterWeights.length; i++) {
parameterWeights[i] = 1;
}
}
public DeltaExchangeOperator(Parameter parameter, int[] parameterWeights, double delta, double weight, boolean isIntegerOperator, CoercionMode mode) {
super(mode);
this.parameter = parameter;
this.delta = delta;
setWeight(weight);
this.isIntegerOperator = isIntegerOperator;
this.parameterWeights = parameterWeights;
if (isIntegerOperator && delta != Math.round(delta)) {
throw new IllegalArgumentException("Can't be an integer operator if delta is not integer");
}
}
/**
* @return the parameter this operator acts on.
*/
public Parameter getParameter() {
return parameter;
}
/**
* change the parameter and return the hastings ratio.
* performs a delta exchange operation between two scalars in the vector
* and return the hastings ratio.
*/
public final double doOperation() {
// get two dimensions
final int dim = parameter.getDimension();
final int dim1 = MathUtils.nextInt(dim);
int dim2 = dim1;
while (dim1 == dim2) {
dim2 = MathUtils.nextInt(dim);
}
double scalar1 = parameter.getParameterValue(dim1);
double scalar2 = parameter.getParameterValue(dim2);
if (isIntegerOperator) {
int d = MathUtils.nextInt((int) Math.round(delta)) + 1;
if (parameterWeights[dim1] != parameterWeights[dim2]) throw new RuntimeException();
scalar1 = Math.round(scalar1 - d);
scalar2 = Math.round(scalar2 + d);
} else {
// exchange a random delta
final double d = MathUtils.nextDouble() * delta;
scalar1 -= d;
if (parameterWeights[dim1] != parameterWeights[dim2]) {
scalar2 += d * (double) parameterWeights[dim1] / (double) parameterWeights[dim2];
} else {
scalar2 += d;
}
}
Bounds<Double> bounds = parameter.getBounds();
if (scalar1 < bounds.getLowerLimit(dim1) ||
scalar1 > bounds.getUpperLimit(dim1) ||
scalar2 < bounds.getLowerLimit(dim2) ||
scalar2 > bounds.getUpperLimit(dim2)) {
return Double.NEGATIVE_INFINITY;
}
parameter.setParameterValue(dim1, scalar1);
parameter.setParameterValue(dim2, scalar2);
// symmetrical move so return a zero hasting ratio
return 0.0;
}
// Interface MCMCOperator
public final String getOperatorName() {
return parameter.getParameterName();
}
public double getCoercableParameter() {
return Math.log(delta);
}
public void setCoercableParameter(double value) {
delta = Math.exp(value);
}
public double getRawParameter() {
return delta;
}
public double getTargetAcceptanceProbability() {
return 0.234;
}
public final String getPerformanceSuggestion() {
double prob = MCMCOperator.Utils.getAcceptanceProbability(this);
double targetProb = getTargetAcceptanceProbability();
double d = OperatorUtils.optimizeWindowSize(delta, parameter.getParameterValue(0) * 2.0, prob, targetProb);
if (prob < getMinimumGoodAcceptanceLevel()) {
return "Try decreasing delta to about " + d;
} else if (prob > getMaximumGoodAcceptanceLevel()) {
return "Try increasing delta to about " + d;
} else return "";
}
public String toString() {
return getOperatorName() + "(windowsize=" + delta + ")";
}
// Private instance variables
private Parameter parameter = null;
private final int[] parameterWeights;
private double delta = 0.02;
private boolean isIntegerOperator = false;
}