org.apache.commons.math3.ode.sampling
Class StepNormalizer

java.lang.Object
  extended by org.apache.commons.math3.ode.sampling.StepNormalizer
All Implemented Interfaces:
StepHandler

public class StepNormalizer
extends Object
implements StepHandler

This class wraps an object implementing FixedStepHandler into a StepHandler.

This wrapper allows to use fixed step handlers with general integrators which cannot guaranty their integration steps will remain constant and therefore only accept general step handlers.

The stepsize used is selected at construction time. The handleStep method of the underlying FixedStepHandler object is called at normalized times. The normalized times can be influenced by the StepNormalizerMode and StepNormalizerBounds.

There is no constraint on the integrator, it can use any time step it needs (time steps longer or shorter than the fixed time step and non-integer ratios are all allowed).

Examples (step size = 0.5)
Start timeEnd time DirectionMode BoundsOutput
0.33.1forwardINCREMENTNEITHER0.8, 1.3, 1.8, 2.3, 2.8
0.33.1forwardINCREMENTFIRST0.3, 0.8, 1.3, 1.8, 2.3, 2.8
0.33.1forwardINCREMENTLAST0.8, 1.3, 1.8, 2.3, 2.8, 3.1
0.33.1forwardINCREMENTBOTH0.3, 0.8, 1.3, 1.8, 2.3, 2.8, 3.1
0.33.1forwardMULTIPLESNEITHER0.5, 1.0, 1.5, 2.0, 2.5, 3.0
0.33.1forwardMULTIPLESFIRST0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0
0.33.1forwardMULTIPLESLAST0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.1
0.33.1forwardMULTIPLESBOTH0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.1
0.03.0forwardINCREMENTNEITHER0.5, 1.0, 1.5, 2.0, 2.5, 3.0
0.03.0forwardINCREMENTFIRST0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0
0.03.0forwardINCREMENTLAST0.5, 1.0, 1.5, 2.0, 2.5, 3.0
0.03.0forwardINCREMENTBOTH0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0
0.03.0forwardMULTIPLESNEITHER0.5, 1.0, 1.5, 2.0, 2.5, 3.0
0.03.0forwardMULTIPLESFIRST0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0
0.03.0forwardMULTIPLESLAST0.5, 1.0, 1.5, 2.0, 2.5, 3.0
0.03.0forwardMULTIPLESBOTH0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0
3.10.3backwardINCREMENTNEITHER2.6, 2.1, 1.6, 1.1, 0.6
3.10.3backwardINCREMENTFIRST3.1, 2.6, 2.1, 1.6, 1.1, 0.6
3.10.3backwardINCREMENTLAST2.6, 2.1, 1.6, 1.1, 0.6, 0.3
3.10.3backwardINCREMENTBOTH3.1, 2.6, 2.1, 1.6, 1.1, 0.6, 0.3
3.10.3backwardMULTIPLESNEITHER3.0, 2.5, 2.0, 1.5, 1.0, 0.5
3.10.3backwardMULTIPLESFIRST3.1, 3.0, 2.5, 2.0, 1.5, 1.0, 0.5
3.10.3backwardMULTIPLESLAST3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.3
3.10.3backwardMULTIPLESBOTH3.1, 3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.3
3.00.0backwardINCREMENTNEITHER2.5, 2.0, 1.5, 1.0, 0.5, 0.0
3.00.0backwardINCREMENTFIRST3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.0
3.00.0backwardINCREMENTLAST2.5, 2.0, 1.5, 1.0, 0.5, 0.0
3.00.0backwardINCREMENTBOTH3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.0
3.00.0backwardMULTIPLESNEITHER2.5, 2.0, 1.5, 1.0, 0.5, 0.0
3.00.0backwardMULTIPLESFIRST3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.0
3.00.0backwardMULTIPLESLAST2.5, 2.0, 1.5, 1.0, 0.5, 0.0
3.00.0backwardMULTIPLESBOTH3.0, 2.5, 2.0, 1.5, 1.0, 0.5, 0.0

Since:
1.2
Version:
$Id: StepNormalizer.java 1416643 2012-12-03 19:37:14Z tn $
See Also:
StepHandler, FixedStepHandler, StepNormalizerMode, StepNormalizerBounds

Field Summary
private  StepNormalizerBounds bounds
          The step normalizer bounds settings to use.
private  double firstTime
          First step time.
private  boolean forward
          Integration direction indicator.
private  double h
          Fixed time step.
private  FixedStepHandler handler
          Underlying step handler.
private  double[] lastDerivatives
          Last derivatives vector.
private  double[] lastState
          Last state vector.
private  double lastTime
          Last step time.
private  StepNormalizerMode mode
          The step normalizer mode to use.
 
Constructor Summary
StepNormalizer(double h, FixedStepHandler handler)
          Simple constructor.
StepNormalizer(double h, FixedStepHandler handler, StepNormalizerBounds bounds)
          Simple constructor.
StepNormalizer(double h, FixedStepHandler handler, StepNormalizerMode mode)
          Simple constructor.
StepNormalizer(double h, FixedStepHandler handler, StepNormalizerMode mode, StepNormalizerBounds bounds)
          Simple constructor.
 
Method Summary
private  void doNormalizedStep(boolean isLast)
          Invokes the underlying step handler for the current normalized step.
 void handleStep(StepInterpolator interpolator, boolean isLast)
          Handle the last accepted step
 void init(double t0, double[] y0, double t)
          Initialize step handler at the start of an ODE integration.
private  boolean isNextInStep(double nextTime, StepInterpolator interpolator)
          Returns a value indicating whether the next normalized time is in the current step.
private  void storeStep(StepInterpolator interpolator, double t)
          Stores the interpolated information for the given time in the current state.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

h

private double h
Fixed time step.


handler

private final FixedStepHandler handler
Underlying step handler.


firstTime

private double firstTime
First step time.


lastTime

private double lastTime
Last step time.


lastState

private double[] lastState
Last state vector.


lastDerivatives

private double[] lastDerivatives
Last derivatives vector.


forward

private boolean forward
Integration direction indicator.


bounds

private final StepNormalizerBounds bounds
The step normalizer bounds settings to use.


mode

private final StepNormalizerMode mode
The step normalizer mode to use.

Constructor Detail

StepNormalizer

public StepNormalizer(double h,
                      FixedStepHandler handler)
Simple constructor. Uses INCREMENT mode, and FIRST bounds setting, for backwards compatibility.

Parameters:
h - fixed time step (sign is not used)
handler - fixed time step handler to wrap

StepNormalizer

public StepNormalizer(double h,
                      FixedStepHandler handler,
                      StepNormalizerMode mode)
Simple constructor. Uses FIRST bounds setting.

Parameters:
h - fixed time step (sign is not used)
handler - fixed time step handler to wrap
mode - step normalizer mode to use
Since:
3.0

StepNormalizer

public StepNormalizer(double h,
                      FixedStepHandler handler,
                      StepNormalizerBounds bounds)
Simple constructor. Uses INCREMENT mode.

Parameters:
h - fixed time step (sign is not used)
handler - fixed time step handler to wrap
bounds - step normalizer bounds setting to use
Since:
3.0

StepNormalizer

public StepNormalizer(double h,
                      FixedStepHandler handler,
                      StepNormalizerMode mode,
                      StepNormalizerBounds bounds)
Simple constructor.

Parameters:
h - fixed time step (sign is not used)
handler - fixed time step handler to wrap
mode - step normalizer mode to use
bounds - step normalizer bounds setting to use
Since:
3.0
Method Detail

init

public void init(double t0,
                 double[] y0,
                 double t)
Initialize step handler at the start of an ODE integration.

This method is called once at the start of the integration. It may be used by the step handler to initialize some internal data if needed.

Specified by:
init in interface StepHandler
Parameters:
t0 - start value of the independent time variable
y0 - array containing the start value of the state vector
t - target time for the integration

handleStep

public void handleStep(StepInterpolator interpolator,
                       boolean isLast)
                throws MaxCountExceededException
Handle the last accepted step

Specified by:
handleStep in interface StepHandler
Parameters:
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), it should build a local copy using the clone method and store this copy.
isLast - true if the step is the last one
Throws:
MaxCountExceededException - if the interpolator throws one because the number of functions evaluations is exceeded

isNextInStep

private boolean isNextInStep(double nextTime,
                             StepInterpolator interpolator)
Returns a value indicating whether the next normalized time is in the current step.

Parameters:
nextTime - the next normalized time
interpolator - interpolator for the last accepted step, to use to get the end time of the current step
Returns:
value indicating whether the next normalized time is in the current step

doNormalizedStep

private void doNormalizedStep(boolean isLast)
Invokes the underlying step handler for the current normalized step.

Parameters:
isLast - true if the step is the last one

storeStep

private void storeStep(StepInterpolator interpolator,
                       double t)
                throws MaxCountExceededException
Stores the interpolated information for the given time in the current state.

Parameters:
interpolator - interpolator for the last accepted step, to use to get the interpolated information
t - the time for which to store the interpolated information
Throws:
MaxCountExceededException - if the interpolator throws one because the number of functions evaluations is exceeded


Copyright (c) 2003-2013 Apache Software Foundation