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Commons Math example source code file (StepHandlerWithJacobians.java)

This example Commons Math source code file (StepHandlerWithJacobians.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons Math tags/keywords

derivativeexception, derivativeexception, stephandlerwithjacobians, stephandlerwithjacobians

The Commons Math StepHandlerWithJacobians.java source code

/*
 * 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.math.ode.jacobians;

import org.apache.commons.math.ode.DerivativeException;

/**
 * This interface represents a handler that should be called after
 * each successful step.
 *
 * <p>The ODE integrators compute the evolution of the state vector at
 * some grid points that depend on their own internal algorithm. Once
 * they have found a new grid point (possibly after having computed
 * several evaluation of the derivative at intermediate points), they
 * provide it to objects implementing this interface. These objects
 * typically either ignore the intermediate steps and wait for the
 * last one, store the points in an ephemeris, or forward them to
 * specialized processing or output methods.</p>
 *
 * <p>Note that is is possible to register a {@link
 * org.apache.commons.math.ode.sampling.StepHandler classical step handler}
 * in the low level integrator used to build a {@link FirstOrderIntegratorWithJacobians}
 * rather than implementing this class. The step handlers registered at low level
 * will see the big compound state whether the step handlers defined by this interface
 * see the original state, and its jacobians in separate arrays.</p>
 *
 * <p>The compound state is guaranteed to contain the original state in the first
 * elements, followed by the jacobian with respect to initial state (in row order),
 * followed by the jacobian with respect to parameters (in row order). If for example
 * the original state dimension is 6 and there are 3 parameters, the compound state will
 * be a 60 elements array. The first 6 elements will be the original state, the next 36
 * elements will be the jacobian with respect to initial state, and the remaining 18 elements
 * will be the jacobian with respect to parameters.</p>
 *
 * <p>Dealing with low level step handlers is cumbersome if one really needs the jacobians
 * in these methods, but it also prevents many data being copied back and forth between
 * state and jacobians on one side and compound state on the other side. So for performance
 * reasons, it is recommended to use this interface <em>only if jacobians are really
 * needed and to use lower level handlers if only state is needed.</p>
 *
 * @see FirstOrderIntegratorWithJacobians
 * @see StepInterpolatorWithJacobians
 * @version $Revision: 920131 $ $Date: 2010-03-07 17:19:18 -0500 (Sun, 07 Mar 2010) $
 * @since 2.1
 */

public interface StepHandlerWithJacobians {

  /** Determines whether this handler needs dense output.
   * <p>This method allows the integrator to avoid performing extra
   * computation if the handler does not need dense output.</p>
   * @return true if the handler needs dense output
   */
  boolean requiresDenseOutput();

  /** Reset the step handler.
   * Initialize the internal data as required before the first step is
   * handled.
   */
  void reset();

  /**
   * 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, as the
   * {@link org.apache.commons.math.ode.ContinuousOutputModel
   * ContinuousOutputModel} class does), it should build a local copy
   * using the clone method of the interpolator and store this copy.
   * Keeping only a reference to the interpolator and reusing it will
   * result in unpredictable behavior (potentially crashing the application).
   * @param isLast true if the step is the last one
   * @throws DerivativeException this exception is propagated to the
   * caller if the underlying user function triggers one
   */
  void handleStep(StepInterpolatorWithJacobians interpolator, boolean isLast) throws DerivativeException;

}

Other Commons Math examples (source code examples)

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