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Java example source code file (MidpointFieldStepInterpolator.java)

This example Java source code file (MidpointFieldStepInterpolator.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

fieldequationsmapper, fieldodestateandderivative, midpointfieldstepinterpolator, override, realfieldelement, rungekuttafieldstepinterpolator, suppresswarnings

The MidpointFieldStepInterpolator.java Java example 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,
 * See the License for the specific language governing permissions and
 * limitations under the License.

package org.apache.commons.math3.ode.nonstiff;

import org.apache.commons.math3.Field;
import org.apache.commons.math3.RealFieldElement;
import org.apache.commons.math3.ode.FieldEquationsMapper;
import org.apache.commons.math3.ode.FieldODEStateAndDerivative;

 * This class implements a step interpolator for second order
 * Runge-Kutta integrator.
 * <p>This interpolator computes dense output inside the last
 * step computed. The interpolation equation is consistent with the
 * integration scheme :
 * <ul>
 *   <li>Using reference point at step start:
* y(t<sub>n + θ h) = y (tn) + θ h [(1 - θ) y'1 + θ y'2] * </li> * <li>Using reference point at step end:
* y(t<sub>n + θ h) = y (tn + h) + (1-θ) h [θ y'1 - (1+θ) y'2] * </li> * </ul> * </p> * * where θ belongs to [0 ; 1] and where y'<sub>1 and y'2 are the two * evaluations of the derivatives already computed during the * step.</p> * * @see MidpointFieldIntegrator * @param <T> the type of the field elements * @since 3.6 */ class MidpointFieldStepInterpolator<T extends RealFieldElement extends RungeKuttaFieldStepInterpolator<T> { /** Simple constructor. * @param field field to which the time and state vector elements belong * @param forward integration direction indicator * @param yDotK slopes at the intermediate points * @param globalPreviousState start of the global step * @param globalCurrentState end of the global step * @param softPreviousState start of the restricted step * @param softCurrentState end of the restricted step * @param mapper equations mapper for the all equations */ MidpointFieldStepInterpolator(final Field<T> field, final boolean forward, final T[][] yDotK, final FieldODEStateAndDerivative<T> globalPreviousState, final FieldODEStateAndDerivative<T> globalCurrentState, final FieldODEStateAndDerivative<T> softPreviousState, final FieldODEStateAndDerivative<T> softCurrentState, final FieldEquationsMapper<T> mapper) { super(field, forward, yDotK, globalPreviousState, globalCurrentState, softPreviousState, softCurrentState, mapper); } /** {@inheritDoc} */ @Override protected MidpointFieldStepInterpolator<T> create(final Field newField, final boolean newForward, final T[][] newYDotK, final FieldODEStateAndDerivative<T> newGlobalPreviousState, final FieldODEStateAndDerivative<T> newGlobalCurrentState, final FieldODEStateAndDerivative<T> newSoftPreviousState, final FieldODEStateAndDerivative<T> newSoftCurrentState, final FieldEquationsMapper<T> newMapper) { return new MidpointFieldStepInterpolator<T>(newField, newForward, newYDotK, newGlobalPreviousState, newGlobalCurrentState, newSoftPreviousState, newSoftCurrentState, newMapper); } /** {@inheritDoc} */ @SuppressWarnings("unchecked") @Override protected FieldODEStateAndDerivative<T> computeInterpolatedStateAndDerivatives(final FieldEquationsMapper mapper, final T time, final T theta, final T thetaH, final T oneMinusThetaH) { final T coeffDot2 = theta.multiply(2); final T coeffDot1 = time.getField().getOne().subtract(coeffDot2); final T[] interpolatedState; final T[] interpolatedDerivatives; if (getGlobalPreviousState() != null && theta.getReal() <= 0.5) { final T coeff1 = theta.multiply(oneMinusThetaH); final T coeff2 = theta.multiply(thetaH); interpolatedState = previousStateLinearCombination(coeff1, coeff2); interpolatedDerivatives = derivativeLinearCombination(coeffDot1, coeffDot2); } else { final T coeff1 = oneMinusThetaH.multiply(theta); final T coeff2 = oneMinusThetaH.multiply(theta.add(1)).negate(); interpolatedState = currentStateLinearCombination(coeff1, coeff2); interpolatedDerivatives = derivativeLinearCombination(coeffDot1, coeffDot2); } return new FieldODEStateAndDerivative<T>(time, interpolatedState, interpolatedDerivatives); } }

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