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.sampling; 19 20 import java.io.Externalizable; 21 22 import org.apache.commons.math.ode.DerivativeException; 23 24 /** This interface represents an interpolator over the last step 25 * during an ODE integration. 26 * 27 * <p>The various ODE integrators provide objects implementing this 28 * interface to the step handlers. These objects are often custom 29 * objects tightly bound to the integrator internal algorithms. The 30 * handlers can use these objects to retrieve the state vector at 31 * intermediate times between the previous and the current grid points 32 * (this feature is often called dense output).</p> 33 * <p>One important thing to note is that the step handlers may be so 34 * tightly bound to the integrators that they often share some internal 35 * state arrays. This imply that one should <em>never</em> use a direct 36 * reference to a step interpolator outside of the step handler, either 37 * for future use or for use in another thread. If such a need arise, the 38 * step interpolator <em>must</em> be copied using the dedicated 39 * {@link #copy()} method. 40 * </p> 41 * 42 * @see org.apache.commons.math.ode.FirstOrderIntegrator 43 * @see org.apache.commons.math.ode.SecondOrderIntegrator 44 * @see StepHandler 45 * @version $Revision: 1073158 $ $Date: 2011-02-21 22:46:52 +0100 (lun. 21 fvr. 2011) $ 46 * @since 1.2 47 */ 48 49 public interface StepInterpolator extends Externalizable { 50 51 /** 52 * Get the previous grid point time. 53 * @return previous grid point time 54 */ 55 double getPreviousTime(); 56 57 /** 58 * Get the current grid point time. 59 * @return current grid point time 60 */ 61 double getCurrentTime(); 62 63 /** 64 * Get the time of the interpolated point. 65 * If {@link #setInterpolatedTime} has not been called, it returns 66 * the current grid point time. 67 * @return interpolation point time 68 */ 69 double getInterpolatedTime(); 70 71 /** 72 * Set the time of the interpolated point. 73 * <p>Setting the time outside of the current step is now allowed, but 74 * should be used with care since the accuracy of the interpolator will 75 * probably be very poor far from this step. This allowance has been 76 * added to simplify implementation of search algorithms near the 77 * step endpoints.</p> 78 * <p>Setting the time changes the instance internal state. If a 79 * specific state must be preserved, a copy of the instance must be 80 * created using {@link #copy()}.</p> 81 * @param time time of the interpolated point 82 */ 83 void setInterpolatedTime(double time); 84 85 /** 86 * Get the state vector of the interpolated point. 87 * <p>The returned vector is a reference to a reused array, so 88 * it should not be modified and it should be copied if it needs 89 * to be preserved across several calls.</p> 90 * @return state vector at time {@link #getInterpolatedTime} 91 * @see #getInterpolatedDerivatives() 92 * @exception DerivativeException if user code called from step interpolator 93 * finalization triggers one 94 */ 95 double[] getInterpolatedState() throws DerivativeException; 96 97 /** 98 * Get the derivatives of the state vector of the interpolated point. 99 * <p>The returned vector is a reference to a reused array, so 100 * it should not be modified and it should be copied if it needs 101 * to be preserved across several calls.</p> 102 * @return derivatives of the state vector at time {@link #getInterpolatedTime} 103 * @see #getInterpolatedState() 104 * @exception DerivativeException if user code called from step interpolator 105 * finalization triggers one 106 * @since 2.0 107 */ 108 double[] getInterpolatedDerivatives() throws DerivativeException; 109 110 /** Check if the natural integration direction is forward. 111 * <p>This method provides the integration direction as specified by 112 * the integrator itself, it avoid some nasty problems in 113 * degenerated cases like null steps due to cancellation at step 114 * initialization, step control or discrete events 115 * triggering.</p> 116 * @return true if the integration variable (time) increases during 117 * integration 118 */ 119 boolean isForward(); 120 121 /** Copy the instance. 122 * <p>The copied instance is guaranteed to be independent from the 123 * original one. Both can be used with different settings for 124 * interpolated time without any side effect.</p> 125 * @return a deep copy of the instance, which can be used independently. 126 * @exception DerivativeException if user code called from step interpolator 127 * finalization triggers one 128 * @see #setInterpolatedTime(double) 129 */ 130 StepInterpolator copy() throws DerivativeException; 131 132 } 133
