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Diffstat (limited to 'src/main/java/org/apache/commons/math/ode/jacobians/EventHandlerWithJacobians.java')
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diff --git a/src/main/java/org/apache/commons/math/ode/jacobians/EventHandlerWithJacobians.java b/src/main/java/org/apache/commons/math/ode/jacobians/EventHandlerWithJacobians.java new file mode 100644 index 0000000..80d6c6e --- /dev/null +++ b/src/main/java/org/apache/commons/math/ode/jacobians/EventHandlerWithJacobians.java @@ -0,0 +1,226 @@ +/* + * 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.events.EventException; + +/** This interface represents a handler for discrete events triggered + * during ODE integration. + * + * <p>Some events can be triggered at discrete times as an ODE problem + * is solved. This occurs for example when the integration process + * should be stopped as some state is reached (G-stop facility) when the + * precise date is unknown a priori, or when the derivatives have + * discontinuities, or simply when the user wants to monitor some + * states boundaries crossings. + * </p> + * + * <p>These events are defined as occurring when a <code>g</code> + * switching function sign changes.</p> + * + * <p>Since events are only problem-dependent and are triggered by the + * independent <i>time</i> variable and the state vector, they can + * occur at virtually any time, unknown in advance. The integrators will + * take care to avoid sign changes inside the steps, they will reduce + * the step size when such an event is detected in order to put this + * event exactly at the end of the current step. This guarantees that + * step interpolation (which always has a one step scope) is relevant + * even in presence of discontinuities. This is independent from the + * stepsize control provided by integrators that monitor the local + * error (this event handling feature is available for all integrators, + * including fixed step ones).</p> + * + * <p>Note that is is possible to register a {@link + * org.apache.commons.math.ode.events.EventHandler classical event handler} + * in the low level integrator used to build a {@link FirstOrderIntegratorWithJacobians} + * rather than implementing this class. The event handlers registered at low level + * will see the big compound state whether the event 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 event 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</em> if jacobians are really + * needed and to use lower level handlers if only state is needed.</p> + * + * @version $Revision: 1037341 $ $Date: 2010-11-20 22:58:35 +0100 (sam. 20 nov. 2010) $ + * @since 2.1 + * @deprecated as of 2.2 the complete package is deprecated, it will be replaced + * in 3.0 by a completely rewritten implementation + */ +@Deprecated +public interface EventHandlerWithJacobians { + + /** Stop indicator. + * <p>This value should be used as the return value of the {@link + * #eventOccurred eventOccurred} method when the integration should be + * stopped after the event ending the current step.</p> + */ + int STOP = 0; + + /** Reset state indicator. + * <p>This value should be used as the return value of the {@link + * #eventOccurred eventOccurred} method when the integration should + * go on after the event ending the current step, with a new state + * vector (which will be retrieved thanks to the {@link #resetState + * resetState} method).</p> + */ + int RESET_STATE = 1; + + /** Reset derivatives indicator. + * <p>This value should be used as the return value of the {@link + * #eventOccurred eventOccurred} method when the integration should + * go on after the event ending the current step, with a new derivatives + * vector (which will be retrieved thanks to the {@link + * org.apache.commons.math.ode.FirstOrderDifferentialEquations#computeDerivatives} + * method).</p> + */ + int RESET_DERIVATIVES = 2; + + /** Continue indicator. + * <p>This value should be used as the return value of the {@link + * #eventOccurred eventOccurred} method when the integration should go + * on after the event ending the current step.</p> + */ + int CONTINUE = 3; + + /** Compute the value of the switching function. + + * <p>The discrete events are generated when the sign of this + * switching function changes. The integrator will take care to change + * the stepsize in such a way these events occur exactly at step boundaries. + * The switching function must be continuous in its roots neighborhood + * (but not necessarily smooth), as the integrator will need to find its + * roots to locate precisely the events.</p> + + * @param t current value of the independent <i>time</i> variable + * @param y array containing the current value of the state vector + * @param dydy0 array containing the current value of the jacobian of + * the state vector with respect to initial state + * @param dydp array containing the current value of the jacobian of + * the state vector with respect to parameters + * @return value of the g switching function + * @exception EventException if the switching function cannot be evaluated + */ + double g(double t, double[] y, double[][] dydy0, double[][] dydp) + throws EventException; + + /** Handle an event and choose what to do next. + + * <p>This method is called when the integrator has accepted a step + * ending exactly on a sign change of the function, just <em>before</em> + * the step handler itself is called (see below for scheduling). It + * allows the user to update his internal data to acknowledge the fact + * the event has been handled (for example setting a flag in the {@link + * org.apache.commons.math.ode.jacobians.ODEWithJacobians + * differential equations} to switch the derivatives computation in + * case of discontinuity), or to direct the integrator to either stop + * or continue integration, possibly with a reset state or derivatives.</p> + + * <ul> + * <li>if {@link #STOP} is returned, the step handler will be called + * with the <code>isLast</code> flag of the {@link + * org.apache.commons.math.ode.jacobians.StepHandlerWithJacobians#handleStep( + * StepInterpolatorWithJacobians, boolean) handleStep} method set to true and + * the integration will be stopped,</li> + * <li>if {@link #RESET_STATE} is returned, the {@link #resetState + * resetState} method will be called once the step handler has + * finished its task, and the integrator will also recompute the + * derivatives,</li> + * <li>if {@link #RESET_DERIVATIVES} is returned, the integrator + * will recompute the derivatives, + * <li>if {@link #CONTINUE} is returned, no specific action will + * be taken (apart from having called this method) and integration + * will continue.</li> + * </ul> + + * <p>The scheduling between this method and the {@link + * org.apache.commons.math.ode.jacobians.StepHandlerWithJacobians + * StepHandlerWithJacobians} method {@link + * org.apache.commons.math.ode.jacobians.StepHandlerWithJacobians#handleStep( + * StepInterpolatorWithJacobians, boolean) handleStep(interpolator, isLast)} + * is to call this method first and <code>handleStep</code> afterwards. This + * scheduling allows the integrator to pass <code>true</code> as the + * <code>isLast</code> parameter to the step handler to make it aware the step + * will be the last one if this method returns {@link #STOP}. As the + * interpolator may be used to navigate back throughout the last step (as {@link + * org.apache.commons.math.ode.sampling.StepNormalizer StepNormalizer} + * does for example), user code called by this method and user + * code called by step handlers may experience apparently out of order values + * of the independent time variable. As an example, if the same user object + * implements both this {@link EventHandlerWithJacobians EventHandler} interface and the + * {@link org.apache.commons.math.ode.sampling.FixedStepHandler FixedStepHandler} + * interface, a <em>forward</em> integration may call its + * <code>eventOccurred</code> method with t = 10 first and call its + * <code>handleStep</code> method with t = 9 afterwards. Such out of order + * calls are limited to the size of the integration step for {@link + * org.apache.commons.math.ode.sampling.StepHandler variable step handlers} and + * to the size of the fixed step for {@link + * org.apache.commons.math.ode.sampling.FixedStepHandler fixed step handlers}.</p> + + * @param t current value of the independent <i>time</i> variable + * @param y array containing the current value of the state vector + * @param dydy0 array containing the current value of the jacobian of + * the state vector with respect to initial state + * @param dydp array containing the current value of the jacobian of + * the state vector with respect to parameters + * @param increasing if true, the value of the switching function increases + * when times increases around event (note that increase is measured with respect + * to physical time, not with respect to integration which may go backward in time) + * @return indication of what the integrator should do next, this + * value must be one of {@link #STOP}, {@link #RESET_STATE}, + * {@link #RESET_DERIVATIVES} or {@link #CONTINUE} + * @exception EventException if the event occurrence triggers an error + */ + int eventOccurred(double t, double[] y, double[][] dydy0, double[][] dydp, + boolean increasing) throws EventException; + + /** Reset the state prior to continue the integration. + + * <p>This method is called after the step handler has returned and + * before the next step is started, but only when {@link + * #eventOccurred} has itself returned the {@link #RESET_STATE} + * indicator. It allows the user to reset the state vector for the + * next step, without perturbing the step handler of the finishing + * step. If the {@link #eventOccurred} never returns the {@link + * #RESET_STATE} indicator, this function will never be called, and it is + * safe to leave its body empty.</p> + + * @param t current value of the independent <i>time</i> variable + * @param y array containing the current value of the state vector + * the new state should be put in the same array + * @param dydy0 array containing the current value of the jacobian of + * the state vector with respect to initial state, the new jacobian + * should be put in the same array + * @param dydp array containing the current value of the jacobian of + * the state vector with respect to parameters, the new jacobian + * should be put in the same array + * @exception EventException if the state cannot be reseted + */ + void resetState(double t, double[] y, double[][] dydy0, double[][] dydp) + throws EventException; + +} |