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Java example source code file (HighamHall54StepInterpolator.java)

This example Java source code file (HighamHall54StepInterpolator.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

highamhall54stepinterpolator, override, rungekuttastepinterpolator, stepinterpolator

The HighamHall54StepInterpolator.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.ode.sampling.StepInterpolator;

/**
 * This class represents an interpolator over the last step during an
 * ODE integration for the 5(4) Higham and Hall integrator.
 *
 * @see HighamHall54Integrator
 *
 * @since 1.2
 */

class HighamHall54StepInterpolator
  extends RungeKuttaStepInterpolator {

  /** Serializable version identifier */
  private static final long serialVersionUID = 20111120L;

  /** Simple constructor.
   * This constructor builds an instance that is not usable yet, the
   * {@link
   * org.apache.commons.math3.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
   * EmbeddedRungeKuttaIntegrator} uses the prototyping design pattern
   * to create the step interpolators by cloning an uninitialized model
   * and later initializing the copy.
   */
  // CHECKSTYLE: stop RedundantModifier
  // the public modifier here is needed for serialization
  public HighamHall54StepInterpolator() {
    super();
  }
  // CHECKSTYLE: resume RedundantModifier

  /** 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
   */
  HighamHall54StepInterpolator(final HighamHall54StepInterpolator interpolator) {
    super(interpolator);
  }

  /** {@inheritDoc} */
  @Override
  protected StepInterpolator doCopy() {
    return new HighamHall54StepInterpolator(this);
  }


  /** {@inheritDoc} */
  @Override
  protected void computeInterpolatedStateAndDerivatives(final double theta,
                                          final double oneMinusThetaH) {

    final double bDot0 = 1 + theta * (-15.0/2.0 + theta * (16.0 - 10.0 * theta));
    final double bDot2 = theta * (459.0/16.0 + theta * (-729.0/8.0 + 135.0/2.0 * theta));
    final double bDot3 = theta * (-44.0 + theta * (152.0 - 120.0 * theta));
    final double bDot4 = theta * (375.0/16.0 + theta * (-625.0/8.0 + 125.0/2.0 * theta));
    final double bDot5 = theta * 5.0/8.0 * (2 * theta - 1);

    if ((previousState != null) && (theta <= 0.5)) {
        final double hTheta = h * theta;
        final double b0 = hTheta * (1.0 + theta * (-15.0/4.0  + theta * (16.0/3.0 - 5.0/2.0 * theta)));
        final double b2 = hTheta * (      theta * (459.0/32.0 + theta * (-243.0/8.0 + theta * 135.0/8.0)));
        final double b3 = hTheta * (      theta * (-22.0      + theta * (152.0/3.0  + theta * -30.0)));
        final double b4 = hTheta * (      theta * (375.0/32.0 + theta * (-625.0/24.0 + theta * 125.0/8.0)));
        final double b5 = hTheta * (      theta * (-5.0/16.0  + theta *  5.0/12.0));
        for (int i = 0; i < interpolatedState.length; ++i) {
            final double yDot0 = yDotK[0][i];
            final double yDot2 = yDotK[2][i];
            final double yDot3 = yDotK[3][i];
            final double yDot4 = yDotK[4][i];
            final double yDot5 = yDotK[5][i];
            interpolatedState[i] =
                    previousState[i] + b0 * yDot0 + b2 * yDot2 + b3 * yDot3 + b4 * yDot4 + b5 * yDot5;
            interpolatedDerivatives[i] =
                    bDot0 * yDot0 + bDot2 * yDot2 + bDot3 * yDot3 + bDot4 * yDot4 + bDot5 * yDot5;
        }
    } else {
        final double theta2 = theta * theta;
        final double b0 = h * (-1.0/12.0 + theta * (1.0 + theta * (-15.0/4.0 + theta * (16.0/3.0 + theta * -5.0/2.0))));
        final double b2 = h * (-27.0/32.0 + theta2 * (459.0/32.0 + theta * (-243.0/8.0 + theta * 135.0/8.0)));
        final double b3 = h * (4.0/3.0 + theta2 * (-22.0 + theta * (152.0/3.0  + theta * -30.0)));
        final double b4 = h * (-125.0/96.0 + theta2 * (375.0/32.0 + theta * (-625.0/24.0 + theta * 125.0/8.0)));
        final double b5 = h * (-5.0/48.0 + theta2 * (-5.0/16.0 + theta * 5.0/12.0));
        for (int i = 0; i < interpolatedState.length; ++i) {
            final double yDot0 = yDotK[0][i];
            final double yDot2 = yDotK[2][i];
            final double yDot3 = yDotK[3][i];
            final double yDot4 = yDotK[4][i];
            final double yDot5 = yDotK[5][i];
            interpolatedState[i] =
                    currentState[i] + b0 * yDot0 + b2 * yDot2 + b3 * yDot3 + b4 * yDot4 + b5 * yDot5;
            interpolatedDerivatives[i] =
                    bDot0 * yDot0 + bDot2 * yDot2 + bDot3 * yDot3 + bDot4 * yDot4 + bDot5 * yDot5;
        }
    }

  }

}

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