|
Commons Math example source code file (GillStepInterpolator.java)
The Commons Math GillStepInterpolator.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 Gill 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) [ (1 - theta) (1 - 4 theta) y'_1 * + (1 - theta) (1 + 2 theta) ((2-q) y'_2 + (2+q) y'_3) * + (1 + theta + 4 theta^2) y'_4 * ] * </pre> * where theta belongs to [0 ; 1], q = sqrt(2) and where y'_1 to y'_4 * are the four evaluations of the derivatives already computed during * the step.</p> * * @see GillIntegrator * @version $Revision: 811827 $ $Date: 2009-09-06 11:32:50 -0400 (Sun, 06 Sep 2009) $ * @since 1.2 */ class GillStepInterpolator extends RungeKuttaStepInterpolator { /** First Gill coefficient. */ private static final double TWO_MINUS_SQRT_2 = 2 - Math.sqrt(2.0); /** Second Gill coefficient. */ private static final double TWO_PLUS_SQRT_2 = 2 + Math.sqrt(2.0); /** Serializable version identifier */ private static final long serialVersionUID = -107804074496313322L; /** Simple constructor. * This constructor builds an instance that is not usable yet, the * {@link * org.apache.commons.math.ode.sampling.AbstractStepInterpolator#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 later initializing the copy. */ public GillStepInterpolator() { } /** 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 GillStepInterpolator(final GillStepInterpolator interpolator) { super(interpolator); } /** {@inheritDoc} */ @Override protected StepInterpolator doCopy() { return new GillStepInterpolator(this); } /** {@inheritDoc} */ @Override protected void computeInterpolatedStateAndDerivatives(final double theta, final double oneMinusThetaH) throws DerivativeException { final double twoTheta = 2 * theta; final double fourTheta = 4 * theta; final double s = oneMinusThetaH / 6.0; final double oMt = 1 - theta; final double soMt = s * oMt; final double c23 = soMt * (1 + twoTheta); final double coeff1 = soMt * (1 - fourTheta); final double coeff2 = c23 * TWO_MINUS_SQRT_2; final double coeff3 = c23 * TWO_PLUS_SQRT_2; final double coeff4 = s * (1 + theta * (1 + fourTheta)); final double coeffDot1 = theta * (twoTheta - 3) + 1; final double cDot23 = theta * oMt; final double coeffDot2 = cDot23 * TWO_MINUS_SQRT_2; final double coeffDot3 = cDot23 * TWO_PLUS_SQRT_2; final double coeffDot4 = theta * (twoTheta - 1); for (int i = 0; i < interpolatedState.length; ++i) { final double yDot1 = yDotK[0][i]; final double yDot2 = yDotK[1][i]; final double yDot3 = yDotK[2][i]; final double yDot4 = yDotK[3][i]; interpolatedState[i] = currentState[i] - coeff1 * yDot1 - coeff2 * yDot2 - coeff3 * yDot3 - coeff4 * yDot4; interpolatedDerivatives[i] = coeffDot1 * yDot1 + coeffDot2 * yDot2 + coeffDot3 * yDot3 + coeffDot4 * yDot4; } } } Other Commons Math examples (source code examples)Here is a short list of links related to this Commons Math GillStepInterpolator.java source code file: |
... this post is sponsored by my books ... | |
#1 New Release! |
FP Best Seller |
Copyright 1998-2024 Alvin Alexander, alvinalexander.com
All Rights Reserved.
A percentage of advertising revenue from
pages under the /java/jwarehouse
URI on this website is
paid back to open source projects.