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Commons Math example source code file (ClassicalRungeKuttaStepInterpolator.java)
The Commons Math ClassicalRungeKuttaStepInterpolator.java source code/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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 org.apache.commons.math.ode.nonstiff; import org.apache.commons.math.ode.DerivativeException; import org.apache.commons.math.ode.sampling.StepInterpolator; /** * This class implements a step interpolator for the classical fourth * order Runge-Kutta integrator. * * <p>This interpolator allows to compute dense output inside the last * step computed. The interpolation equation is consistent with the * integration scheme : * <pre> * y(t_n + theta h) = y (t_n + h) * + (1 - theta) (h/6) [ (-4 theta^2 + 5 theta - 1) y'_1 * +(4 theta^2 - 2 theta - 2) (y'_2 + y'_3) * -(4 theta^2 + theta + 1) y'_4 * ] * </pre> * * where theta belongs to [0 ; 1] and where y'_1 to y'_4 are the four * evaluations of the derivatives already computed during the * step.</p> * * @see ClassicalRungeKuttaIntegrator * @version $Revision: 782432 $ $Date: 2009-06-07 15:08:26 -0400 (Sun, 07 Jun 2009) $ * @since 1.2 */ class ClassicalRungeKuttaStepInterpolator extends RungeKuttaStepInterpolator { /** Serializable version identifier */ private static final long serialVersionUID = -6576285612589783992L; /** Simple constructor. * This constructor builds an instance that is not usable yet, the * {@link RungeKuttaStepInterpolator#reinitialize} method should be * called before using the instance in order to initialize the * internal arrays. This constructor is used only in order to delay * the initialization in some cases. The {@link RungeKuttaIntegrator} * class uses the prototyping design pattern to create the step * interpolators by cloning an uninitialized model and latter initializing * the copy. */ public ClassicalRungeKuttaStepInterpolator() { } /** Copy constructor. * @param interpolator interpolator to copy from. The copy is a deep * copy: its arrays are separated from the original arrays of the * instance */ public ClassicalRungeKuttaStepInterpolator(final ClassicalRungeKuttaStepInterpolator interpolator) { super(interpolator); } /** {@inheritDoc} */ @Override protected StepInterpolator doCopy() { return new ClassicalRungeKuttaStepInterpolator(this); } /** {@inheritDoc} */ @Override protected void computeInterpolatedStateAndDerivatives(final double theta, final double oneMinusThetaH) throws DerivativeException { final double fourTheta = 4 * theta; final double oneMinusTheta = 1 - theta; final double oneMinus2Theta = 1 - 2 * theta; final double s = oneMinusThetaH / 6.0; final double coeff1 = s * ((-fourTheta + 5) * theta - 1); final double coeff23 = s * (( fourTheta - 2) * theta - 2); final double coeff4 = s * ((-fourTheta - 1) * theta - 1); final double coeffDot1 = oneMinusTheta * oneMinus2Theta; final double coeffDot23 = 2 * theta * oneMinusTheta; final double coeffDot4 = -theta * oneMinus2Theta; for (int i = 0; i < interpolatedState.length; ++i) { final double yDot1 = yDotK[0][i]; final double yDot23 = yDotK[1][i] + yDotK[2][i]; final double yDot4 = yDotK[3][i]; interpolatedState[i] = currentState[i] + coeff1 * yDot1 + coeff23 * yDot23 + coeff4 * yDot4; interpolatedDerivatives[i] = coeffDot1 * yDot1 + coeffDot23 * yDot23 + coeffDot4 * yDot4; } } } Other Commons Math examples (source code examples)Here is a short list of links related to this Commons Math ClassicalRungeKuttaStepInterpolator.java source code file: |
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