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Java example source code file (RungeKuttaFieldStepInterpolator.java)

This example Java source code file (RungeKuttaFieldStepInterpolator.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.

Learn more about this Java project at its project page.

Java - Java tags/keywords

abstractfieldstepinterpolator, fieldequationsmapper, fieldodestateandderivative, override, realfieldelement, rungekuttafieldstepinterpolator

The RungeKuttaFieldStepInterpolator.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,
 * 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.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;
import org.apache.commons.math3.ode.sampling.AbstractFieldStepInterpolator;
import org.apache.commons.math3.util.MathArrays;

/** This class represents an interpolator over the last step during an
 * ODE integration for Runge-Kutta and embedded Runge-Kutta integrators.
 *
 * @see RungeKuttaFieldIntegrator
 * @see EmbeddedRungeKuttaFieldIntegrator
 *
 * @param <T> the type of the field elements
 * @since 3.6
 */

abstract class RungeKuttaFieldStepInterpolator<T extends RealFieldElement
    extends AbstractFieldStepInterpolator<T> {

    /** Field to which the time and state vector elements belong. */
    private final Field<T> field;

    /** Slopes at the intermediate points. */
    private final T[][] yDotK;

    /** 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
     */
    protected RungeKuttaFieldStepInterpolator(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(forward, globalPreviousState, globalCurrentState, softPreviousState, softCurrentState, mapper);
        this.field = field;
        this.yDotK = MathArrays.buildArray(field, yDotK.length, -1);
        for (int i = 0; i < yDotK.length; ++i) {
            this.yDotK[i] = yDotK[i].clone();
        }
    }

    /** {@inheritDoc} */
    @Override
    protected RungeKuttaFieldStepInterpolator<T> create(boolean newForward,
                                                        FieldODEStateAndDerivative<T> newGlobalPreviousState,
                                                        FieldODEStateAndDerivative<T> newGlobalCurrentState,
                                                        FieldODEStateAndDerivative<T> newSoftPreviousState,
                                                        FieldODEStateAndDerivative<T> newSoftCurrentState,
                                                        FieldEquationsMapper<T> newMapper) {
        return create(field, newForward, yDotK,
                      newGlobalPreviousState, newGlobalCurrentState,
                      newSoftPreviousState, newSoftCurrentState,
                      newMapper);
    }

    /** Create a new instance.
     * @param newField field to which the time and state vector elements belong
     * @param newForward integration direction indicator
     * @param newYDotK slopes at the intermediate points
     * @param newGlobalPreviousState start of the global step
     * @param newGlobalCurrentState end of the global step
     * @param newSoftPreviousState start of the restricted step
     * @param newSoftCurrentState end of the restricted step
     * @param newMapper equations mapper for the all equations
     * @return a new instance
     */
    protected abstract RungeKuttaFieldStepInterpolator<T> create(Field newField, boolean newForward, T[][] newYDotK,
                                                                 FieldODEStateAndDerivative<T> newGlobalPreviousState,
                                                                 FieldODEStateAndDerivative<T> newGlobalCurrentState,
                                                                 FieldODEStateAndDerivative<T> newSoftPreviousState,
                                                                 FieldODEStateAndDerivative<T> newSoftCurrentState,
                                                                 FieldEquationsMapper<T> newMapper);

    /** Compute a state by linear combination added to previous state.
     * @param coefficients coefficients to apply to the method staged derivatives
     * @return combined state
     */
    protected final T[] previousStateLinearCombination(final T ... coefficients) {
        return combine(getPreviousState().getState(),
                       coefficients);
    }

    /** Compute a state by linear combination added to current state.
     * @param coefficients coefficients to apply to the method staged derivatives
     * @return combined state
     */
    protected T[] currentStateLinearCombination(final T ... coefficients) {
        return combine(getCurrentState().getState(),
                       coefficients);
    }

    /** Compute a state derivative by linear combination.
     * @param coefficients coefficients to apply to the method staged derivatives
     * @return combined state
     */
    protected T[] derivativeLinearCombination(final T ... coefficients) {
        return combine(MathArrays.buildArray(field, yDotK[0].length), coefficients);
    }

    /** Linearly combine arrays.
     * @param a array to add to
     * @param coefficients coefficients to apply to the method staged derivatives
     * @return a itself, as a convenience for fluent API
     */
    private T[] combine(final T[] a, final T ... coefficients) {
        for (int i = 0; i < a.length; ++i) {
            for (int k = 0; k < coefficients.length; ++k) {
                a[i] = a[i].add(coefficients[k].multiply(yDotK[k][i]));
            }
        }
        return a;
    }

}

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