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;
019    
020    import org.apache.commons.math.ode.events.EventHandler;
021    import org.apache.commons.math.ode.sampling.StepHandler;
022    
023    /** This interface represents a first order integrator for
024     * differential equations.
025    
026     * <p>The classes which are devoted to solve first order differential
027     * equations should implement this interface. The problems which can
028     * be handled should implement the {@link
029     * FirstOrderDifferentialEquations} interface.</p>
030     *
031     * @see FirstOrderDifferentialEquations
032     * @see StepHandler
033     * @see EventHandler
034     * @version $Revision: 674820 $ $Date: 2008-07-08 09:37:09 -0400 (Tue, 08 Jul 2008) $
035     * @since 1.2
036     */
037    
038    public interface FirstOrderIntegrator extends ODEIntegrator {
039    
040      /** Integrate the differential equations up to the given time.
041       * <p>This method solves an Initial Value Problem (IVP).</p>
042       * <p>Since this method stores some internal state variables made
043       * available in its public interface during integration ({@link
044       * #getCurrentSignedStepsize()}), it is <em>not</em> thread-safe.</p>
045       * @param equations differential equations to integrate
046       * @param t0 initial time
047       * @param y0 initial value of the state vector at t0
048       * @param t target time for the integration
049       * (can be set to a value smaller than <code>t0</code> for backward integration)
050       * @param y placeholder where to put the state vector at each successful
051       *  step (and hence at the end of integration), can be the same object as y0
052       * @return stop time, will be the same as target time if integration reached its
053       * target, but may be different if some {@link EventHandler} stops it at some point.
054       * @throws IntegratorException if the integrator cannot perform integration
055       * @throws DerivativeException this exception is propagated to the caller if
056       * the underlying user function triggers one
057       */
058      public double integrate (FirstOrderDifferentialEquations equations,
059                               double t0, double[] y0,
060                               double t, double[] y)
061        throws DerivativeException, IntegratorException;
062    
063    }