FieldStepNormalizer.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.CalculusFieldElement;
  26. import org.hipparchus.ode.FieldODEStateAndDerivative;
  27. import org.hipparchus.util.FastMath;
  28. import org.hipparchus.util.Precision;

  30. /**
  31.  * This class wraps an object implementing {@link FieldODEFixedStepHandler}
  32.  * into a {@link FieldODEStepHandler}.

  34.  * <p>This wrapper allows to use fixed step handlers with general
  35.  * integrators which cannot guaranty their integration steps will
  36.  * remain constant and therefore only accept general step
  37.  * handlers.</p>
  38.  *
  39.  * <p>The stepsize used is selected at construction time. The {@link
  40.  * FieldODEFixedStepHandler#handleStep handleStep} method of the underlying
  41.  * {@link FieldODEFixedStepHandler} object is called at normalized times. The
  42.  * normalized times can be influenced by the {@link StepNormalizerMode} and
  43.  * {@link StepNormalizerBounds}.</p>
  44.  *
  45.  * <p>There is no constraint on the integrator, it can use any time step
  46.  * it needs (time steps longer or shorter than the fixed time step and
  47.  * non-integer ratios are all allowed).</p>
  48.  *
  49.  * <table border="">
  50.  * <caption>Examples (step size = 0.5)</caption>
  51.  * <tr ><td>Start time</td><td>End time</td>
  52.  *  <td>Direction</td><td>{@link StepNormalizerMode Mode}</td>
  53.  *  <td>{@link StepNormalizerBounds Bounds}</td><td>Output</td></tr>
  54.  * <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>
  55.  * <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>
  56.  * <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>
  57.  * <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>
  58.  * <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>
  59.  * <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>
  60.  * <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>
  61.  * <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>
  62.  * <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>
  63.  * <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>
  64.  * <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>
  65.  * <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>
  66.  * <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>
  67.  * <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>
  68.  * <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>
  69.  * <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>
  70.  * <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>
  71.  * <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>
  72.  * <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>
  73.  * <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>
  74.  * <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>
  75.  * <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>
  76.  * <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>
  77.  * <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>
  78.  * <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>
  79.  * <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>
  80.  * <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>
  81.  * <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>
  82.  * <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>
  83.  * <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>
  84.  * <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>
  85.  * <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>
  86.  * </table>
  87.  *
  88.  * @param <T> the type of the field elements
  89.  * @see FieldODEStepHandler
  90.  * @see FieldODEFixedStepHandler
  91.  * @see StepNormalizerMode
  92.  * @see StepNormalizerBounds
  93.  */

  95. public class FieldStepNormalizer<T extends CalculusFieldElement<T>> implements FieldODEStepHandler<T> {

  97.     /** Fixed time step. */
  98.     private double h;

  100.     /** Underlying step handler. */
  101.     private final FieldODEFixedStepHandler<T> handler;

  103.     /** First step state. */
  104.     private FieldODEStateAndDerivative<T> first;

  106.     /** Last step step. */
  107.     private FieldODEStateAndDerivative<T> last;

  109.     /** Integration direction indicator. */
  110.     private boolean forward;

  112.     /** The step normalizer bounds settings to use. */
  113.     private final StepNormalizerBounds bounds;

  115.     /** The step normalizer mode to use. */
  116.     private final StepNormalizerMode mode;

  118.     /** Simple constructor. Uses {@link StepNormalizerMode#INCREMENT INCREMENT}
  119.      * mode, and {@link StepNormalizerBounds#FIRST FIRST} bounds setting, for
  120.      * backwards compatibility.
  121.      * @param h fixed time step (sign is not used)
  122.      * @param handler fixed time step handler to wrap
  123.      */
  124.     public FieldStepNormalizer(final double h, final FieldODEFixedStepHandler<T> handler) {
  125.         this(h, handler, StepNormalizerMode.INCREMENT,
  126.              StepNormalizerBounds.FIRST);
  127.     }

  129.     /** Simple constructor. Uses {@link StepNormalizerBounds#FIRST FIRST}
  130.      * bounds setting.
  131.      * @param h fixed time step (sign is not used)
  132.      * @param handler fixed time step handler to wrap
  133.      * @param mode step normalizer mode to use
  134.      */
  135.     public FieldStepNormalizer(final double h, final FieldODEFixedStepHandler<T> handler,
  136.                                final StepNormalizerMode mode) {
  137.         this(h, handler, mode, StepNormalizerBounds.FIRST);
  138.     }

  140.     /** Simple constructor. Uses {@link StepNormalizerMode#INCREMENT INCREMENT}
  141.      * mode.
  142.      * @param h fixed time step (sign is not used)
  143.      * @param handler fixed time step handler to wrap
  144.      * @param bounds step normalizer bounds setting to use
  145.      */
  146.     public FieldStepNormalizer(final double h, final FieldODEFixedStepHandler<T> handler,
  147.                                final StepNormalizerBounds bounds) {
  148.         this(h, handler, StepNormalizerMode.INCREMENT, bounds);
  149.     }

  151.     /** Simple constructor.
  152.      * @param h fixed time step (sign is not used)
  153.      * @param handler fixed time step handler to wrap
  154.      * @param mode step normalizer mode to use
  155.      * @param bounds step normalizer bounds setting to use
  156.      */
  157.     public FieldStepNormalizer(final double h, final FieldODEFixedStepHandler<T> handler,
  158.                                final StepNormalizerMode mode, final StepNormalizerBounds bounds) {
  159.         this.h       = FastMath.abs(h);
  160.         this.handler = handler;
  161.         this.mode    = mode;
  162.         this.bounds  = bounds;
  163.         first        = null;
  164.         last         = null;
  165.         forward      = true;
  166.     }

  168.     /** {@inheritDoc} */
  169.     @Override
  170.     public void init(final FieldODEStateAndDerivative<T> initialState, final T finalTime) {

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

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

  179.     }

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

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

  190.             // Take the integration direction into account.
  191.             forward = interpolator.isForward();
  192.             if (!forward) {
  193.                 h = -h;
  194.             }
  195.         }

  197.         // Calculate next normalized step time.
  198.         T nextTime = (mode == StepNormalizerMode.INCREMENT) ?
  199.                      last.getTime().add(h) :
  200.                      last.getTime().getField().getZero().add((FastMath.floor(last.getTime().getReal() / h) + 1) * h);
  201.         if (mode == StepNormalizerMode.MULTIPLES &&
  202.             Precision.equals(nextTime.getReal(), last.getTime().getReal(), 1)) {
  203.             nextTime = nextTime.add(h);
  204.         }

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

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

  215.             // Move on to the next step.
  216.             nextTime = nextTime.add(h);
  217.             nextInStep = isNextInStep(nextTime, interpolator);
  218.         }
  219.     }

  221.     /** {@inheritDoc} */
  222.     @Override
  223.     public void finish(final FieldODEStateAndDerivative<T> finalState) {
  224.         // There will be no more steps. The stored one should be given to
  225.         // the handler. We may have to output one more step. Only the last
  226.         // one of those should be flagged as being the last.
  227.         final boolean addLast = bounds.lastIncluded() && last.getTime().getReal() != finalState.getTime().getReal();
  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(final T nextTime, final FieldODEStateInterpolator<T> interpolator) {
  245.         return forward ?
  246.                nextTime.getReal() <= interpolator.getCurrentState().getTime().getReal() :
  247.                nextTime.getReal() >= interpolator.getCurrentState().getTime().getReal();
  248.     }

  250.     /**
  251.      * Invokes the underlying step handler for the current normalized step.
  252.      * @param isLast true if the step is the last one
  253.      */
  254.     private void doNormalizedStep(final boolean isLast) {
  255.         if (!bounds.firstIncluded() && first.getTime().getReal() == last.getTime().getReal()) {
  256.             return;
  257.         }
  258.         handler.handleStep(last, isLast);
  259.     }

  261. }
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