StepNormalizer.java

  1. /*
  2.  * Licensed to the Apache Software Foundation (ASF) under one or more
  3.  * contributor license agreements.  See the NOTICE file distributed with
  4.  * this work for additional information regarding copyright ownership.
  5.  * The ASF licenses this file to You under the Apache License, Version 2.0
  6.  * (the "License"); you may not use this file except in compliance with
  7.  * the License.  You may obtain a copy of the License at
  8.  *
  9.  *      https://www.apache.org/licenses/LICENSE-2.0
  10.  *
  11.  * Unless required by applicable law or agreed to in writing, software
  12.  * distributed under the License is distributed on an "AS IS" BASIS,
  13.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14.  * See the License for the specific language governing permissions and
  15.  * limitations under the License.
  16.  */

  18. /*
  19.  * This is not the original file distributed by the Apache Software Foundation
  20.  * It has been modified by the Hipparchus project
  21.  */

  23. package org.hipparchus.ode.sampling;

  25. import org.hipparchus.ode.ODEStateAndDerivative;
  26. import org.hipparchus.util.FastMath;
  27. import org.hipparchus.util.Precision;

  29. /**
  30.  * This class wraps an object implementing {@link ODEFixedStepHandler}
  31.  * into a {@link ODEStepHandler}.

  33.  * <p>This wrapper allows to use fixed step handlers with general
  34.  * integrators which cannot guaranty their integration steps will
  35.  * remain constant and therefore only accept general step
  36.  * handlers.</p>
  37.  *
  38.  * <p>The stepsize used is selected at construction time. The {@link
  39.  * ODEFixedStepHandler#handleStep handleStep} method of the underlying
  40.  * {@link ODEFixedStepHandler} object is called at normalized times. The
  41.  * normalized times can be influenced by the {@link StepNormalizerMode} and
  42.  * {@link StepNormalizerBounds}.</p>
  43.  *
  44.  * <p>There is no constraint on the integrator, it can use any time step
  45.  * it needs (time steps longer or shorter than the fixed time step and
  46.  * non-integer ratios are all allowed).</p>
  47.  *
  48.  * <table border="">
  49.  * <caption>Examples (step size = 0.5)</caption>
  50.  * <tr ><td>Start time</td><td>End time</td>
  51.  *  <td>Direction</td><td>{@link StepNormalizerMode Mode}</td>
  52.  *  <td>{@link StepNormalizerBounds Bounds}</td><td>Output</td></tr>
  53.  * <tr><td>0.3</td><td>3.1</td><td>forward</td><td>{@link StepNormalizerMode#INCREMENT INCREMENT}</td><td>{@link StepNormalizerBounds#NEITHER NEITHER}</td><td>0.8, 1.3, 1.8, 2.3, 2.8</td></tr>
  54.  * <tr><td>0.3</td><td>3.1</td><td>forward</td><td>{@link StepNormalizerMode#INCREMENT INCREMENT}</td><td>{@link StepNormalizerBounds#FIRST FIRST}</td><td>0.3, 0.8, 1.3, 1.8, 2.3, 2.8</td></tr>
  55.  * <tr><td>0.3</td><td>3.1</td><td>forward</td><td>{@link StepNormalizerMode#INCREMENT INCREMENT}</td><td>{@link StepNormalizerBounds#LAST LAST}</td><td>0.8, 1.3, 1.8, 2.3, 2.8, 3.1</td></tr>
  56.  * <tr><td>0.3</td><td>3.1</td><td>forward</td><td>{@link StepNormalizerMode#INCREMENT INCREMENT}</td><td>{@link StepNormalizerBounds#BOTH BOTH}</td><td>0.3, 0.8, 1.3, 1.8, 2.3, 2.8, 3.1</td></tr>
  57.  * <tr><td>0.3</td><td>3.1</td><td>forward</td><td>{@link StepNormalizerMode#MULTIPLES MULTIPLES}</td><td>{@link StepNormalizerBounds#NEITHER NEITHER}</td><td>0.5, 1.0, 1.5, 2.0, 2.5, 3.0</td></tr>
  58.  * <tr><td>0.3</td><td>3.1</td><td>forward</td><td>{@link StepNormalizerMode#MULTIPLES MULTIPLES}</td><td>{@link StepNormalizerBounds#FIRST FIRST}</td><td>0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0</td></tr>
  59.  * <tr><td>0.3</td><td>3.1</td><td>forward</td><td>{@link StepNormalizerMode#MULTIPLES MULTIPLES}</td><td>{@link StepNormalizerBounds#LAST LAST}</td><td>0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.1</td></tr>
  60.  * <tr><td>0.3</td><td>3.1</td><td>forward</td><td>{@link StepNormalizerMode#MULTIPLES MULTIPLES}</td><td>{@link StepNormalizerBounds#BOTH BOTH}</td><td>0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.1</td></tr>
  61.  * <tr><td>0.0</td><td>3.0</td><td>forward</td><td>{@link StepNormalizerMode#INCREMENT INCREMENT}</td><td>{@link StepNormalizerBounds#NEITHER NEITHER}</td><td>0.5, 1.0, 1.5, 2.0, 2.5, 3.0</td></tr>
  62.  * <tr><td>0.0</td><td>3.0</td><td>forward</td><td>{@link StepNormalizerMode#INCREMENT INCREMENT}</td><td>{@link StepNormalizerBounds#FIRST FIRST}</td><td>0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0</td></tr>
  63.  * <tr><td>0.0</td><td>3.0</td><td>forward</td><td>{@link StepNormalizerMode#INCREMENT INCREMENT}</td><td>{@link StepNormalizerBounds#LAST LAST}</td><td>0.5, 1.0, 1.5, 2.0, 2.5, 3.0</td></tr>
  64.  * <tr><td>0.0</td><td>3.0</td><td>forward</td><td>{@link StepNormalizerMode#INCREMENT INCREMENT}</td><td>{@link StepNormalizerBounds#BOTH BOTH}</td><td>0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0</td></tr>
  65.  * <tr><td>0.0</td><td>3.0</td><td>forward</td><td>{@link StepNormalizerMode#MULTIPLES MULTIPLES}</td><td>{@link StepNormalizerBounds#NEITHER NEITHER}</td><td>0.5, 1.0, 1.5, 2.0, 2.5, 3.0</td></tr>
  66.  * <tr><td>0.0</td><td>3.0</td><td>forward</td><td>{@link StepNormalizerMode#MULTIPLES MULTIPLES}</td><td>{@link StepNormalizerBounds#FIRST FIRST}</td><td>0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0</td></tr>
  67.  * <tr><td>0.0</td><td>3.0</td><td>forward</td><td>{@link StepNormalizerMode#MULTIPLES MULTIPLES}</td><td>{@link StepNormalizerBounds#LAST LAST}</td><td>0.5, 1.0, 1.5, 2.0, 2.5, 3.0</td></tr>
  68.  * <tr><td>0.0</td><td>3.0</td><td>forward</td><td>{@link StepNormalizerMode#MULTIPLES MULTIPLES}</td><td>{@link StepNormalizerBounds#BOTH BOTH}</td><td>0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0</td></tr>
  69.  * <tr><td>3.1</td><td>0.3</td><td>backward</td><td>{@link StepNormalizerMode#INCREMENT INCREMENT}</td><td>{@link StepNormalizerBounds#NEITHER NEITHER}</td><td>2.6, 2.1, 1.6, 1.1, 0.6</td></tr>
  70.  * <tr><td>3.1</td><td>0.3</td><td>backward</td><td>{@link StepNormalizerMode#INCREMENT INCREMENT}</td><td>{@link StepNormalizerBounds#FIRST FIRST}</td><td>3.1, 2.6, 2.1, 1.6, 1.1, 0.6</td></tr>
  71.  * <tr><td>3.1</td><td>0.3</td><td>backward</td><td>{@link StepNormalizerMode#INCREMENT INCREMENT}</td><td>{@link StepNormalizerBounds#LAST LAST}</td><td>2.6, 2.1, 1.6, 1.1, 0.6, 0.3</td></tr>
  72.  * <tr><td>3.1</td><td>0.3</td><td>backward</td><td>{@link StepNormalizerMode#INCREMENT INCREMENT}</td><td>{@link StepNormalizerBounds#BOTH BOTH}</td><td>3.1, 2.6, 2.1, 1.6, 1.1, 0.6, 0.3</td></tr>
  73.  * <tr><td>3.1</td><td>0.3</td><td>backward</td><td>{@link StepNormalizerMode#MULTIPLES MULTIPLES}</td><td>{@link StepNormalizerBounds#NEITHER NEITHER}</td><td>3.0, 2.5, 2.0, 1.5, 1.0, 0.5</td></tr>
  74.  * <tr><td>3.1</td><td>0.3</td><td>backward</td><td>{@link StepNormalizerMode#MULTIPLES MULTIPLES}</td><td>{@link StepNormalizerBounds#FIRST FIRST}</td><td>3.1, 3.0, 2.5, 2.0, 1.5, 1.0, 0.5</td></tr>
  75.  * <tr><td>3.1</td><td>0.3</td><td>backward</td><td>{@link StepNormalizerMode#MULTIPLES MULTIPLES}</td><td>{@link StepNormalizerBounds#LAST LAST}</td><td>3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.3</td></tr>
  76.  * <tr><td>3.1</td><td>0.3</td><td>backward</td><td>{@link StepNormalizerMode#MULTIPLES MULTIPLES}</td><td>{@link StepNormalizerBounds#BOTH BOTH}</td><td>3.1, 3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.3</td></tr>
  77.  * <tr><td>3.0</td><td>0.0</td><td>backward</td><td>{@link StepNormalizerMode#INCREMENT INCREMENT}</td><td>{@link StepNormalizerBounds#NEITHER NEITHER}</td><td>2.5, 2.0, 1.5, 1.0, 0.5, 0.0</td></tr>
  78.  * <tr><td>3.0</td><td>0.0</td><td>backward</td><td>{@link StepNormalizerMode#INCREMENT INCREMENT}</td><td>{@link StepNormalizerBounds#FIRST FIRST}</td><td>3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.0</td></tr>
  79.  * <tr><td>3.0</td><td>0.0</td><td>backward</td><td>{@link StepNormalizerMode#INCREMENT INCREMENT}</td><td>{@link StepNormalizerBounds#LAST LAST}</td><td>2.5, 2.0, 1.5, 1.0, 0.5, 0.0</td></tr>
  80.  * <tr><td>3.0</td><td>0.0</td><td>backward</td><td>{@link StepNormalizerMode#INCREMENT INCREMENT}</td><td>{@link StepNormalizerBounds#BOTH BOTH}</td><td>3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.0</td></tr>
  81.  * <tr><td>3.0</td><td>0.0</td><td>backward</td><td>{@link StepNormalizerMode#MULTIPLES MULTIPLES}</td><td>{@link StepNormalizerBounds#NEITHER NEITHER}</td><td>2.5, 2.0, 1.5, 1.0, 0.5, 0.0</td></tr>
  82.  * <tr><td>3.0</td><td>0.0</td><td>backward</td><td>{@link StepNormalizerMode#MULTIPLES MULTIPLES}</td><td>{@link StepNormalizerBounds#FIRST FIRST}</td><td>3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.0</td></tr>
  83.  * <tr><td>3.0</td><td>0.0</td><td>backward</td><td>{@link StepNormalizerMode#MULTIPLES MULTIPLES}</td><td>{@link StepNormalizerBounds#LAST LAST}</td><td>2.5, 2.0, 1.5, 1.0, 0.5, 0.0</td></tr>
  84.  * <tr><td>3.0</td><td>0.0</td><td>backward</td><td>{@link StepNormalizerMode#MULTIPLES MULTIPLES}</td><td>{@link StepNormalizerBounds#BOTH BOTH}</td><td>3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.0</td></tr>
  85.  * </table>
  86.  *
  87.  * @see ODEStepHandler
  88.  * @see ODEFixedStepHandler
  89.  * @see StepNormalizerMode
  90.  * @see StepNormalizerBounds
  91.  */

  93. public class StepNormalizer implements ODEStepHandler {

  95.     /** Fixed time step. */
  96.     private double h;

  98.     /** Underlying step handler. */
  99.     private final ODEFixedStepHandler handler;

  101.     /** First step state. */
  102.     private ODEStateAndDerivative first;

  104.     /** Last step step. */
  105.     private ODEStateAndDerivative last;

  107.     /** Integration direction indicator. */
  108.     private boolean forward;

  110.     /** The step normalizer bounds settings to use. */
  111.     private final StepNormalizerBounds bounds;

  113.     /** The step normalizer mode to use. */
  114.     private final StepNormalizerMode mode;

  116.     /** Simple constructor. Uses {@link StepNormalizerMode#INCREMENT INCREMENT}
  117.      * mode, and {@link StepNormalizerBounds#FIRST FIRST} bounds setting, for
  118.      * backwards compatibility.
  119.      * @param h fixed time step (sign is not used)
  120.      * @param handler fixed time step handler to wrap
  121.      */
  122.     public StepNormalizer(final double h, final ODEFixedStepHandler handler) {
  123.         this(h, handler, StepNormalizerMode.INCREMENT,
  124.              StepNormalizerBounds.FIRST);
  125.     }

  127.     /** Simple constructor. Uses {@link StepNormalizerBounds#FIRST FIRST}
  128.      * bounds setting.
  129.      * @param h fixed time step (sign is not used)
  130.      * @param handler fixed time step handler to wrap
  131.      * @param mode step normalizer mode to use
  132.      */
  133.     public StepNormalizer(final double h, final ODEFixedStepHandler handler,
  134.                           final StepNormalizerMode mode) {
  135.         this(h, handler, mode, StepNormalizerBounds.FIRST);
  136.     }

  138.     /** Simple constructor. Uses {@link StepNormalizerMode#INCREMENT INCREMENT}
  139.      * mode.
  140.      * @param h fixed time step (sign is not used)
  141.      * @param handler fixed time step handler to wrap
  142.      * @param bounds step normalizer bounds setting to use
  143.      */
  144.     public StepNormalizer(final double h, final ODEFixedStepHandler handler,
  145.                           final StepNormalizerBounds bounds) {
  146.         this(h, handler, StepNormalizerMode.INCREMENT, bounds);
  147.     }

  149.     /** Simple constructor.
  150.      * @param h fixed time step (sign is not used)
  151.      * @param handler fixed time step handler to wrap
  152.      * @param mode step normalizer mode to use
  153.      * @param bounds step normalizer bounds setting to use
  154.      */
  155.     public StepNormalizer(final double h, final ODEFixedStepHandler handler,
  156.                           final StepNormalizerMode mode,
  157.                           final StepNormalizerBounds bounds) {
  158.         this.h          = FastMath.abs(h);
  159.         this.handler    = handler;
  160.         this.mode       = mode;
  161.         this.bounds     = bounds;
  162.         first           = null;
  163.         last            = null;
  164.         forward         = true;
  165.     }

  167.     /** {@inheritDoc} */
  168.     @Override
  169.     public void init(final ODEStateAndDerivative initialState, final double finalTime) {

  171.         first           = null;
  172.         last            = null;
  173.         forward         = true;

  175.         // initialize the underlying handler
  176.         handler.init(initialState, finalTime);

  178.     }

  180.     /** {@inheritDoc} */
  181.     @Override
  182.     public void handleStep(final ODEStateInterpolator interpolator) {
  183.         // The first time, update the last state with the start information.
  184.         if (last == null) {

  186.             first   = interpolator.getPreviousState();
  187.             last    = first;

  189.             // Take the integration direction into account.
  190.             forward = interpolator.isForward();
  191.             if (!forward) {
  192.                 h = -h;
  193.             }
  194.         }

  196.         // Calculate next normalized step time.
  197.         double nextTime = (mode == StepNormalizerMode.INCREMENT) ?
  198.                           last.getTime() + h :
  199.                           (FastMath.floor(last.getTime() / h) + 1) * h;
  200.         if (mode == StepNormalizerMode.MULTIPLES &&
  201.             Precision.equals(nextTime, last.getTime(), 1)) {
  202.             nextTime += h;
  203.         }

  205.         // Process normalized steps as long as they are in the current step.
  206.         boolean nextInStep = isNextInStep(nextTime, interpolator);
  207.         while (nextInStep) {
  208.             // Output the stored previous step.
  209.             doNormalizedStep(false);

  211.             // Store the next step as last step.
  212.             last = interpolator.getInterpolatedState(nextTime);

  214.             // Move on to the next step.
  215.             nextTime += h;
  216.             nextInStep = isNextInStep(nextTime, interpolator);
  217.         }
  218.     }

  220.     /** {@inheritDoc} */
  221.     @Override
  222.     public void finish(ODEStateAndDerivative finalState) {
  223.             // There will be no more steps. The stored one should be given to
  224.             // the handler. We may have to output one more step. Only the last
  225.             // one of those should be flagged as being the last.
  226.             boolean addLast = bounds.lastIncluded() &&
  227.                               last.getTime() != finalState.getTime();
  228.             doNormalizedStep(!addLast);
  229.             if (addLast) {
  230.                 last = finalState;
  231.                 doNormalizedStep(true);
  232.             }
  233.     }

  235.     /**
  236.      * Returns a value indicating whether the next normalized time is in the
  237.      * current step.
  238.      * @param nextTime the next normalized time
  239.      * @param interpolator interpolator for the last accepted step, to use to
  240.      * get the end time of the current step
  241.      * @return value indicating whether the next normalized time is in the
  242.      * current step
  243.      */
  244.     private boolean isNextInStep(double nextTime,
  245.                                  ODEStateInterpolator interpolator) {
  246.         return forward ?
  247.                nextTime <= interpolator.getCurrentState().getTime() :
  248.                nextTime >= interpolator.getCurrentState().getTime();
  249.     }

  251.     /**
  252.      * Invokes the underlying step handler for the current normalized step.
  253.      * @param isLast true if the step is the last one
  254.      */
  255.     private void doNormalizedStep(boolean isLast) {
  256.         if (!bounds.firstIncluded() && first.getTime() == last.getTime()) {
  257.             return;
  258.         }
  259.         handler.handleStep(last, isLast);
  260.     }

  262. }
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