Java tutorial
/** * Copyright (C) 2011 - present by OpenGamma Inc. and the OpenGamma group of companies * * Please see distribution for license. */ package com.opengamma.analytics.financial.model.interestrate.definition; import it.unimi.dsi.fastutil.doubles.DoubleArrayList; import java.util.Arrays; import org.apache.commons.lang.ObjectUtils; import com.opengamma.util.ArgumentChecker; /** * Parameters related to the G2++ model (equivalent to Hull-White two factors) with piecewise constant volatility. * Reference: Brigo D. anf Mercurio F. Interest Rate Models: Theory and practice. 2001 - Section 4.2. */ public class G2ppPiecewiseConstantParameters { /** * The mean reversion speed parameters (two parameters). */ private final double[] _meanReversion; /** * The volatility parameters. The volatility is constant between the volatility times. Volatility in t is _volatility[i] for t between _volatilityTime[i] and _volatilityTime[i+1]. * There are two volatility list, one for each factor. */ private final DoubleArrayList[] _volatility = new DoubleArrayList[2]; /** * The times separating the constant volatility periods. The time should be sorted by increasing order. The first time is 0 and the last time is 1000 (represents infinity). * The extra time are added in the constructor. */ private final DoubleArrayList _volatilityTime; /** * The model correlation. */ private final double _correlation; /** * The time used to represent infinity. */ private static final double VOLATILITY_TIME_INFINITY = 1000.0; /** * Constructor from the model parameters. * @param meanReversion The mean reversion speed (2) parameters. * @param volatility The volatility parameters. There are two volatility list, one for each factor. * @param volatilityTime The times separating the constant volatility periods. * @param correlation The model correlation. */ public G2ppPiecewiseConstantParameters(final double[] meanReversion, final double[][] volatility, final double[] volatilityTime, final double correlation) { ArgumentChecker.notNull(meanReversion, "mean reversion"); ArgumentChecker.notNull(volatility, "volatility"); ArgumentChecker.notNull(volatilityTime, "volatility time"); ArgumentChecker.isTrue(meanReversion.length == 2, "Two mean reversions required"); ArgumentChecker.isTrue(volatility.length == 2, "Two volatility arrays required"); ArgumentChecker.isTrue(volatility[0].length == volatility[1].length, "Volatility length"); ArgumentChecker.isTrue(volatility[0].length == volatilityTime.length + 1, "Number of times incorrect; had {}, need {}", volatilityTime.length + 1, volatility[0].length); _meanReversion = meanReversion; _volatility[0] = new DoubleArrayList(volatility[0]); _volatility[1] = new DoubleArrayList(volatility[1]); final double[] volatilityTimeArray = new double[volatilityTime.length + 2]; volatilityTimeArray[0] = 0.0; volatilityTimeArray[volatilityTime.length + 1] = VOLATILITY_TIME_INFINITY; System.arraycopy(volatilityTime, 0, volatilityTimeArray, 1, volatilityTime.length); _volatilityTime = new DoubleArrayList(volatilityTimeArray); // TODO: check that the time are increasing. _correlation = correlation; } /** * Gets the mean reversion speed parameters. * @return The mean reversion speed parameters. */ public double[] getMeanReversion() { return _meanReversion; } /** * Gets the volatility parameters. * @return The volatility parameters. */ public DoubleArrayList[] getVolatility() { return _volatility; } /** * Sets the volatility parameters. * @param volatility The volatility parameters. */ public void setVolatility(final double[][] volatility) { ArgumentChecker.isTrue(volatility.length == 2, "Two volatility arrays required"); ArgumentChecker.isTrue(volatility[0].length == volatility[1].length, "Volatility length"); ArgumentChecker.isTrue(volatility[0].length == _volatilityTime.size() - 1, "Volatility length"); _volatility[0] = new DoubleArrayList(volatility[0]); _volatility[1] = new DoubleArrayList(volatility[1]); } /** * Gets the correlation. * @return The correlation */ public double getCorrelation() { return _correlation; } /** * Gets the times separating the constant volatility periods. * @return The times. */ public double[] getVolatilityTime() { return _volatilityTime.toDoubleArray(); } /** * Gets the last volatility of the volatility list. * @return The last volatility. */ public double[] getLastVolatilities() { return new double[] { _volatility[0].get(_volatility[0].size() - 1), _volatility[1].get(_volatility[1].size() - 1) }; } /** * Sets the last volatilities of the volatility lists. * @param volatility The replacing volatility. */ public void setLastVolatilities(final double[] volatility) { ArgumentChecker.isTrue(volatility.length == 2, "Two volatilities required"); _volatility[0].set(_volatility[0].size() - 1, volatility[0]); _volatility[1].set(_volatility[1].size() - 1, volatility[1]); } /** * Add an extra volatilities and volatility time at the end of the lists. * @param volatility The volatilities. Array of dimension 2. * @param volatilityTime The times separating the constant volatility periods. Must be larger than the previous one. */ public void addVolatility(final double[] volatility, final double volatilityTime) { ArgumentChecker.isTrue(volatility.length == 2, "Two volatilities required"); ArgumentChecker.isTrue(volatilityTime > _volatilityTime.get(_volatilityTime.size() - 2), "Volatility times should be increasing"); _volatility[0].add(volatility[0]); _volatility[1].add(volatility[1]); _volatilityTime.set(_volatilityTime.size() - 1, volatilityTime); _volatilityTime.add(VOLATILITY_TIME_INFINITY); } @Override public int hashCode() { final int prime = 31; int result = 1; long temp; temp = Double.doubleToLongBits(_correlation); result = prime * result + (int) (temp ^ (temp >>> 32)); result = prime * result + Arrays.hashCode(_meanReversion); result = prime * result + Arrays.hashCode(_volatility); result = prime * result + _volatilityTime.hashCode(); return result; } @Override public boolean equals(final Object obj) { if (this == obj) { return true; } if (obj == null) { return false; } if (getClass() != obj.getClass()) { return false; } final G2ppPiecewiseConstantParameters other = (G2ppPiecewiseConstantParameters) obj; if (Double.doubleToLongBits(_correlation) != Double.doubleToLongBits(other._correlation)) { return false; } if (!Arrays.equals(_meanReversion, other._meanReversion)) { return false; } if (!Arrays.equals(_volatility, other._volatility)) { return false; } if (!ObjectUtils.equals(_volatilityTime, other._volatilityTime)) { return false; } return true; } }