    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    }