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Java example source code file (LutherIntegrator.java)

This example Java source code file (LutherIntegrator.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

lutherintegrator, lutherstepinterpolator, rungekuttaintegrator, static_a, static_b, static_c

The LutherIntegrator.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.util.FastMath;


/**
 * This class implements the Luther sixth order Runge-Kutta
 * integrator for Ordinary Differential Equations.

 * <p>
 * This method is described in H. A. Luther 1968 paper <a
 * href="http://www.ams.org/journals/mcom/1968-22-102/S0025-5718-68-99876-1/S0025-5718-68-99876-1.pdf">
 * An explicit Sixth-Order Runge-Kutta Formula</a>.
 * </p>

 * <p>This method is an explicit Runge-Kutta method, its Butcher-array
 * is the following one :
 * <pre>
 *        0   |               0                     0                     0                     0                     0                     0
 *        1   |               1                     0                     0                     0                     0                     0
 *       1/2  |              3/8                   1/8                    0                     0                     0                     0
 *       2/3  |              8/27                  2/27                  8/27                   0                     0                     0
 *   (7-q)/14 | (  -21 +   9q)/392    (  -56 +   8q)/392    (  336 -  48q)/392    (  -63 +   3q)/392                  0                     0
 *   (7+q)/14 | (-1155 - 255q)/1960   ( -280 -  40q)/1960   (    0 - 320q)/1960   (   63 + 363q)/1960   ( 2352 + 392q)/1960                 0
 *        1   | (  330 + 105q)/180    (  120 +   0q)/180    ( -200 + 280q)/180    (  126 - 189q)/180    ( -686 - 126q)/180     ( 490 -  70q)/180
 *            |--------------------------------------------------------------------------------------------------------------------------------------------------
 *            |              1/20                   0                   16/45                  0                   49/180                 49/180         1/20
 * </pre>
 * where q = √21</p>
 *
 * @see EulerIntegrator
 * @see ClassicalRungeKuttaIntegrator
 * @see GillIntegrator
 * @see MidpointIntegrator
 * @see ThreeEighthesIntegrator
 * @since 3.3
 */

public class LutherIntegrator extends RungeKuttaIntegrator {

    /** Square root. */
    private static final double Q = FastMath.sqrt(21);

    /** Time steps Butcher array. */
    private static final double[] STATIC_C = {
        1.0, 1.0 / 2.0, 2.0 / 3.0, (7.0 - Q) / 14.0, (7.0 + Q) / 14.0, 1.0
    };

    /** Internal weights Butcher array. */
    private static final double[][] STATIC_A = {
        {                      1.0        },
        {                   3.0 /   8.0,                  1.0 /   8.0  },
        {                   8.0 /   27.0,                 2.0 /   27.0,                  8.0 /   27.0  },
        { (  -21.0 +   9.0 * Q) /  392.0, ( -56.0 +  8.0 * Q) /  392.0, ( 336.0 -  48.0 * Q) /  392.0, (-63.0 +   3.0 * Q) /  392.0 },
        { (-1155.0 - 255.0 * Q) / 1960.0, (-280.0 - 40.0 * Q) / 1960.0, (   0.0 - 320.0 * Q) / 1960.0, ( 63.0 + 363.0 * Q) / 1960.0,   (2352.0 + 392.0 * Q) / 1960.0 },
        { (  330.0 + 105.0 * Q) /  180.0, ( 120.0 +  0.0 * Q) /  180.0, (-200.0 + 280.0 * Q) /  180.0, (126.0 - 189.0 * Q) /  180.0,   (-686.0 - 126.0 * Q) /  180.0,   (490.0 -  70.0 * Q) / 180.0 }
    };

    /** Propagation weights Butcher array. */
    private static final double[] STATIC_B = {
        1.0 / 20.0, 0, 16.0 / 45.0, 0, 49.0 / 180.0, 49.0 / 180.0, 1.0 / 20.0
    };

    /** Simple constructor.
     * Build a fourth-order Luther integrator with the given step.
     * @param step integration step
     */
    public LutherIntegrator(final double step) {
        super("Luther", STATIC_C, STATIC_A, STATIC_B, new LutherStepInterpolator(), step);
    }

}

Other Java examples (source code examples)

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