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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.commons.math.ode;
19  
20  import org.apache.commons.math.ode.events.EventHandler;
21  import org.apache.commons.math.ode.sampling.StepHandler;
22  
23  /** This interface represents a first order integrator for
24   * differential equations.
25  
26   * <p>The classes which are devoted to solve first order differential
27   * equations should implement this interface. The problems which can
28   * be handled should implement the {@link
29   * FirstOrderDifferentialEquations} interface.</p>
30   *
31   * @see FirstOrderDifferentialEquations
32   * @see StepHandler
33   * @see EventHandler
34   * @version $Revision: 674820 $ $Date: 2008-07-08 09:37:09 -0400 (Tue, 08 Jul 2008) $
35   * @since 1.2
36   */
37  
38  public interface FirstOrderIntegrator extends ODEIntegrator {
39  
40    /** Integrate the differential equations up to the given time.
41     * <p>This method solves an Initial Value Problem (IVP).</p>
42     * <p>Since this method stores some internal state variables made
43     * available in its public interface during integration ({@link
44     * #getCurrentSignedStepsize()}), it is <em>not</em> thread-safe.</p>
45     * @param equations differential equations to integrate
46     * @param t0 initial time
47     * @param y0 initial value of the state vector at t0
48     * @param t target time for the integration
49     * (can be set to a value smaller than <code>t0</code> for backward integration)
50     * @param y placeholder where to put the state vector at each successful
51     *  step (and hence at the end of integration), can be the same object as y0
52     * @return stop time, will be the same as target time if integration reached its
53     * target, but may be different if some {@link EventHandler} stops it at some point.
54     * @throws IntegratorException if the integrator cannot perform integration
55     * @throws DerivativeException this exception is propagated to the caller if
56     * the underlying user function triggers one
57     */
58    public double integrate (FirstOrderDifferentialEquations equations,
59                             double t0, double[] y0,
60                             double t, double[] y)
61      throws DerivativeException, IntegratorException;
62  
63  }