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With inspiration from other libraries
/*
* 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.sampling;
import org.apache.commons.math3.RealFieldElement;
import org.apache.commons.math3.exception.MaxCountExceededException;
import org.apache.commons.math3.ode.FieldODEStateAndDerivative;
import org.apache.commons.math3.util.FastMath;
import org.apache.commons.math3.util.Precision;
/**
* This class wraps an object implementing {@link FieldFixedStepHandler}
* into a {@link FieldStepHandler}.
* This wrapper allows to use fixed step handlers with general
* integrators which cannot guaranty their integration steps will
* remain constant and therefore only accept general step
* handlers.
*
* The stepsize used is selected at construction time. The {@link
* FieldFixedStepHandler#handleStep handleStep} method of the underlying
* {@link FieldFixedStepHandler} object is called at normalized times. The
* normalized times can be influenced by the {@link StepNormalizerMode} and
* {@link StepNormalizerBounds}.
*
* There is no constraint on the integrator, it can use any time step
* it needs (time steps longer or shorter than the fixed time step and
* non-integer ratios are all allowed).
*
*
*
* Examples (step size = 0.5) Start time End time
* Direction {@link StepNormalizerMode Mode}
* {@link StepNormalizerBounds Bounds} Output 0.3 3.1 forward {@link StepNormalizerMode#INCREMENT INCREMENT} {@link StepNormalizerBounds#NEITHER NEITHER} 0.8, 1.3, 1.8, 2.3, 2.8 0.3 3.1 forward {@link StepNormalizerMode#INCREMENT INCREMENT} {@link StepNormalizerBounds#FIRST FIRST} 0.3, 0.8, 1.3, 1.8, 2.3, 2.8 0.3 3.1 forward {@link StepNormalizerMode#INCREMENT INCREMENT} {@link StepNormalizerBounds#LAST LAST} 0.8, 1.3, 1.8, 2.3, 2.8, 3.1 0.3 3.1 forward {@link StepNormalizerMode#INCREMENT INCREMENT} {@link StepNormalizerBounds#BOTH BOTH} 0.3, 0.8, 1.3, 1.8, 2.3, 2.8, 3.1 0.3 3.1 forward {@link StepNormalizerMode#MULTIPLES MULTIPLES} {@link StepNormalizerBounds#NEITHER NEITHER} 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 0.3 3.1 forward {@link StepNormalizerMode#MULTIPLES MULTIPLES} {@link StepNormalizerBounds#FIRST FIRST} 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 0.3 3.1 forward {@link StepNormalizerMode#MULTIPLES MULTIPLES} {@link StepNormalizerBounds#LAST LAST} 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.1 0.3 3.1 forward {@link StepNormalizerMode#MULTIPLES MULTIPLES} {@link StepNormalizerBounds#BOTH BOTH} 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.1 0.0 3.0 forward {@link StepNormalizerMode#INCREMENT INCREMENT} {@link StepNormalizerBounds#NEITHER NEITHER} 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 0.0 3.0 forward {@link StepNormalizerMode#INCREMENT INCREMENT} {@link StepNormalizerBounds#FIRST FIRST} 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 0.0 3.0 forward {@link StepNormalizerMode#INCREMENT INCREMENT} {@link StepNormalizerBounds#LAST LAST} 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 0.0 3.0 forward {@link StepNormalizerMode#INCREMENT INCREMENT} {@link StepNormalizerBounds#BOTH BOTH} 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 0.0 3.0 forward {@link StepNormalizerMode#MULTIPLES MULTIPLES} {@link StepNormalizerBounds#NEITHER NEITHER} 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 0.0 3.0 forward {@link StepNormalizerMode#MULTIPLES MULTIPLES} {@link StepNormalizerBounds#FIRST FIRST} 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 0.0 3.0 forward {@link StepNormalizerMode#MULTIPLES MULTIPLES} {@link StepNormalizerBounds#LAST LAST} 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 0.0 3.0 forward {@link StepNormalizerMode#MULTIPLES MULTIPLES} {@link StepNormalizerBounds#BOTH BOTH} 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 3.1 0.3 backward {@link StepNormalizerMode#INCREMENT INCREMENT} {@link StepNormalizerBounds#NEITHER NEITHER} 2.6, 2.1, 1.6, 1.1, 0.6 3.1 0.3 backward {@link StepNormalizerMode#INCREMENT INCREMENT} {@link StepNormalizerBounds#FIRST FIRST} 3.1, 2.6, 2.1, 1.6, 1.1, 0.6 3.1 0.3 backward {@link StepNormalizerMode#INCREMENT INCREMENT} {@link StepNormalizerBounds#LAST LAST} 2.6, 2.1, 1.6, 1.1, 0.6, 0.3 3.1 0.3 backward {@link StepNormalizerMode#INCREMENT INCREMENT} {@link StepNormalizerBounds#BOTH BOTH} 3.1, 2.6, 2.1, 1.6, 1.1, 0.6, 0.3 3.1 0.3 backward {@link StepNormalizerMode#MULTIPLES MULTIPLES} {@link StepNormalizerBounds#NEITHER NEITHER} 3.0, 2.5, 2.0, 1.5, 1.0, 0.5 3.1 0.3 backward {@link StepNormalizerMode#MULTIPLES MULTIPLES} {@link StepNormalizerBounds#FIRST FIRST} 3.1, 3.0, 2.5, 2.0, 1.5, 1.0, 0.5 3.1 0.3 backward {@link StepNormalizerMode#MULTIPLES MULTIPLES} {@link StepNormalizerBounds#LAST LAST} 3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.3 3.1 0.3 backward {@link StepNormalizerMode#MULTIPLES MULTIPLES} {@link StepNormalizerBounds#BOTH BOTH} 3.1, 3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.3 3.0 0.0 backward {@link StepNormalizerMode#INCREMENT INCREMENT} {@link StepNormalizerBounds#NEITHER NEITHER} 2.5, 2.0, 1.5, 1.0, 0.5, 0.0 3.0 0.0 backward {@link StepNormalizerMode#INCREMENT INCREMENT} {@link StepNormalizerBounds#FIRST FIRST} 3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.0 3.0 0.0 backward {@link StepNormalizerMode#INCREMENT INCREMENT} {@link StepNormalizerBounds#LAST LAST} 2.5, 2.0, 1.5, 1.0, 0.5, 0.0 3.0 0.0 backward {@link StepNormalizerMode#INCREMENT INCREMENT} {@link StepNormalizerBounds#BOTH BOTH} 3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.0 3.0 0.0 backward {@link StepNormalizerMode#MULTIPLES MULTIPLES} {@link StepNormalizerBounds#NEITHER NEITHER} 2.5, 2.0, 1.5, 1.0, 0.5, 0.0 3.0 0.0 backward {@link StepNormalizerMode#MULTIPLES MULTIPLES} {@link StepNormalizerBounds#FIRST FIRST} 3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.0 3.0 0.0 backward {@link StepNormalizerMode#MULTIPLES MULTIPLES} {@link StepNormalizerBounds#LAST LAST} 2.5, 2.0, 1.5, 1.0, 0.5, 0.0 3.0 0.0 backward {@link StepNormalizerMode#MULTIPLES MULTIPLES} {@link StepNormalizerBounds#BOTH BOTH} 3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.0
*
*
* @param the type of the field elements
* @see FieldStepHandler
* @see FieldFixedStepHandler
* @see StepNormalizerMode
* @see StepNormalizerBounds
* @since 3.6
*/
public class FieldStepNormalizer> implements FieldStepHandler {
/** Fixed time step. */
private double h;
/** Underlying step handler. */
private final FieldFixedStepHandler handler;
/** First step state. */
private FieldODEStateAndDerivative first;
/** Last step step. */
private FieldODEStateAndDerivative last;
/** Integration direction indicator. */
private boolean forward;
/** The step normalizer bounds settings to use. */
private final StepNormalizerBounds bounds;
/** The step normalizer mode to use. */
private final StepNormalizerMode mode;
/** Simple constructor. Uses {@link StepNormalizerMode#INCREMENT INCREMENT}
* mode, and {@link StepNormalizerBounds#FIRST FIRST} bounds setting, for
* backwards compatibility.
* @param h fixed time step (sign is not used)
* @param handler fixed time step handler to wrap
*/
public FieldStepNormalizer(final double h, final FieldFixedStepHandler handler) {
this(h, handler, StepNormalizerMode.INCREMENT,
StepNormalizerBounds.FIRST);
}
/** Simple constructor. Uses {@link StepNormalizerBounds#FIRST FIRST}
* bounds setting.
* @param h fixed time step (sign is not used)
* @param handler fixed time step handler to wrap
* @param mode step normalizer mode to use
* @since 3.0
*/
public FieldStepNormalizer(final double h, final FieldFixedStepHandler handler,
final StepNormalizerMode mode) {
this(h, handler, mode, StepNormalizerBounds.FIRST);
}
/** Simple constructor. Uses {@link StepNormalizerMode#INCREMENT INCREMENT}
* mode.
* @param h fixed time step (sign is not used)
* @param handler fixed time step handler to wrap
* @param bounds step normalizer bounds setting to use
* @since 3.0
*/
public FieldStepNormalizer(final double h, final FieldFixedStepHandler handler,
final StepNormalizerBounds bounds) {
this(h, handler, StepNormalizerMode.INCREMENT, bounds);
}
/** Simple constructor.
* @param h fixed time step (sign is not used)
* @param handler fixed time step handler to wrap
* @param mode step normalizer mode to use
* @param bounds step normalizer bounds setting to use
* @since 3.0
*/
public FieldStepNormalizer(final double h, final FieldFixedStepHandler handler,
final StepNormalizerMode mode, final StepNormalizerBounds bounds) {
this.h = FastMath.abs(h);
this.handler = handler;
this.mode = mode;
this.bounds = bounds;
first = null;
last = null;
forward = true;
}
/** {@inheritDoc} */
public void init(final FieldODEStateAndDerivative initialState, final T finalTime) {
first = null;
last = null;
forward = true;
// initialize the underlying handler
handler.init(initialState, finalTime);
}
/**
* Handle the last accepted step
* @param interpolator interpolator for the last accepted step. For
* efficiency purposes, the various integrators reuse the same
* object on each call, so if the instance wants to keep it across
* all calls (for example to provide at the end of the integration a
* continuous model valid throughout the integration range), it
* should build a local copy using the clone method and store this
* copy.
* @param isLast true if the step is the last one
* @exception MaxCountExceededException if the interpolator throws one because
* the number of functions evaluations is exceeded
*/
public void handleStep(final FieldStepInterpolator interpolator, final boolean isLast)
throws MaxCountExceededException {
// The first time, update the last state with the start information.
if (last == null) {
first = interpolator.getPreviousState();
last = first;
// Take the integration direction into account.
forward = interpolator.isForward();
if (!forward) {
h = -h;
}
}
// Calculate next normalized step time.
T nextTime = (mode == StepNormalizerMode.INCREMENT) ?
last.getTime().add(h) :
last.getTime().getField().getZero().add((FastMath.floor(last.getTime().getReal() / h) + 1) * h);
if (mode == StepNormalizerMode.MULTIPLES &&
Precision.equals(nextTime.getReal(), last.getTime().getReal(), 1)) {
nextTime = nextTime.add(h);
}
// Process normalized steps as long as they are in the current step.
boolean nextInStep = isNextInStep(nextTime, interpolator);
while (nextInStep) {
// Output the stored previous step.
doNormalizedStep(false);
// Store the next step as last step.
last = interpolator.getInterpolatedState(nextTime);
// Move on to the next step.
nextTime = nextTime.add(h);
nextInStep = isNextInStep(nextTime, interpolator);
}
if (isLast) {
// There will be no more steps. The stored one should be given to
// the handler. We may have to output one more step. Only the last
// one of those should be flagged as being the last.
final boolean addLast = bounds.lastIncluded() &&
last.getTime().getReal() != interpolator.getCurrentState().getTime().getReal();
doNormalizedStep(!addLast);
if (addLast) {
last = interpolator.getCurrentState();
doNormalizedStep(true);
}
}
}
/**
* Returns a value indicating whether the next normalized time is in the
* current step.
* @param nextTime the next normalized time
* @param interpolator interpolator for the last accepted step, to use to
* get the end time of the current step
* @return value indicating whether the next normalized time is in the
* current step
*/
private boolean isNextInStep(final T nextTime, final FieldStepInterpolator interpolator) {
return forward ?
nextTime.getReal() <= interpolator.getCurrentState().getTime().getReal() :
nextTime.getReal() >= interpolator.getCurrentState().getTime().getReal();
}
/**
* Invokes the underlying step handler for the current normalized step.
* @param isLast true if the step is the last one
*/
private void doNormalizedStep(final boolean isLast) {
if (!bounds.firstIncluded() && first.getTime().getReal() == last.getTime().getReal()) {
return;
}
handler.handleStep(last, isLast);
}
}