001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    
018    package org.apache.commons.math.ode.sampling;
019    
020    import org.apache.commons.math.ode.DerivativeException;
021    
022    /**
023     * This interface represents a handler that should be called after
024     * each successful step.
025     *
026     * <p>The ODE integrators compute the evolution of the state vector at
027     * some grid points that depend on their own internal algorithm. Once
028     * they have found a new grid point (possibly after having computed
029     * several evaluation of the derivative at intermediate points), they
030     * provide it to objects implementing this interface. These objects
031     * typically either ignore the intermediate steps and wait for the
032     * last one, store the points in an ephemeris, or forward them to
033     * specialized processing or output methods.</p>
034     *
035     * @see org.apache.commons.math.ode.FirstOrderIntegrator
036     * @see org.apache.commons.math.ode.SecondOrderIntegrator
037     * @see StepInterpolator
038     * @version $Revision: 1073158 $ $Date: 2011-02-21 22:46:52 +0100 (lun. 21 f??vr. 2011) $
039     * @since 1.2
040     */
041    
042    public interface StepHandler {
043    
044      /** Determines whether this handler needs dense output.
045       * <p>This method allows the integrator to avoid performing extra
046       * computation if the handler does not need dense output. If this
047       * method returns false, the integrator will call the {@link
048       * #handleStep} method with a {@link DummyStepInterpolator} rather
049       * than a custom interpolator.</p>
050       * @return true if the handler needs dense output
051       */
052      boolean requiresDenseOutput();
053    
054      /** Reset the step handler.
055       * Initialize the internal data as required before the first step is
056       * handled.
057       */
058      void reset();
059    
060      /**
061       * Handle the last accepted step
062       * @param interpolator interpolator for the last accepted step. For
063       * efficiency purposes, the various integrators reuse the same
064       * object on each call, so if the instance wants to keep it across
065       * all calls (for example to provide at the end of the integration a
066       * continuous model valid throughout the integration range, as the
067       * {@link org.apache.commons.math.ode.ContinuousOutputModel
068       * ContinuousOutputModel} class does), it should build a local copy
069       * using the clone method of the interpolator and store this copy.
070       * Keeping only a reference to the interpolator and reusing it will
071       * result in unpredictable behavior (potentially crashing the application).
072       * @param isLast true if the step is the last one
073       * @exception DerivativeException if user code called from step interpolator
074       * finalization triggers one
075       */
076      void handleStep(StepInterpolator interpolator, boolean isLast) throws DerivativeException;
077    
078    }