Package org.apache.commons.math.ode.sampling

Class AbstractStepInterpolator

java.lang.Object
org.apache.commons.math.ode.sampling.AbstractStepInterpolator
All Implemented Interfaces:
Externalizable, Serializable, StepInterpolator
Direct Known Subclasses:
DummyStepInterpolator, NordsieckStepInterpolator
public abstract class AbstractStepInterpolator extends Object implements StepInterpolator
This abstract class represents an interpolator over the last step during an ODE integration.

The various ODE integrators provide objects extending this class to the step handlers. The handlers can use these objects to retrieve the state vector at intermediate times between the previous and the current grid points (dense output).

Since:
1.2
See Also:

  • Method Details

    • copy

      public StepInterpolator copy() throws DerivativeException
      Copy the instance.

      The copied instance is guaranteed to be independent from the original one. Both can be used with different settings for interpolated time without any side effect.

      Specified by:
      copy in interface StepInterpolator
      Returns:
      a deep copy of the instance, which can be used independently.
      Throws:
      DerivativeException - if user code called from step interpolator finalization triggers one
      See Also:

    • shift

      public void shift()
      Shift one step forward. Copy the current time into the previous time, hence preparing the interpolator for future calls to storeTime

    • storeTime

      public void storeTime(double t)
      Store the current step time.
      Parameters:
      t - current time

    • setSoftPreviousTime

      public void setSoftPreviousTime(double softPreviousTime)
      Restrict step range to a limited part of the global step.

      This method can be used to restrict a step and make it appear as if the original step was smaller. Calling this method only changes the value returned by getPreviousTime(), it does not change any other property

      Parameters:
      softPreviousTime - start of the restricted step
      Since:
      2.2

    • setSoftCurrentTime

      public void setSoftCurrentTime(double softCurrentTime)
      Restrict step range to a limited part of the global step.

      This method can be used to restrict a step and make it appear as if the original step was smaller. Calling this method only changes the value returned by getCurrentTime(), it does not change any other property

      Parameters:
      softCurrentTime - end of the restricted step
      Since:
      2.2

    • getGlobalPreviousTime

      public double getGlobalPreviousTime()
      Get the previous global grid point time.
      Returns:
      previous global grid point time
      Since:
      2.2

    • getGlobalCurrentTime

      public double getGlobalCurrentTime()
      Get the current global grid point time.
      Returns:
      current global grid point time
      Since:
      2.2

    • getPreviousTime

      public double getPreviousTime()
      Get the previous soft grid point time.
      Specified by:
      getPreviousTime in interface StepInterpolator
      Returns:
      previous soft grid point time
      See Also:

    • getCurrentTime

      public double getCurrentTime()
      Get the current soft grid point time.
      Specified by:
      getCurrentTime in interface StepInterpolator
      Returns:
      current soft grid point time
      See Also:

    • getInterpolatedTime

      public double getInterpolatedTime()
      Get the time of the interpolated point. If StepInterpolator.setInterpolatedTime(double) has not been called, it returns the current grid point time.
      Specified by:
      getInterpolatedTime in interface StepInterpolator
      Returns:
      interpolation point time

    • setInterpolatedTime

      public void setInterpolatedTime(double time)
      Set the time of the interpolated point.

      Setting the time outside of the current step is now allowed, but should be used with care since the accuracy of the interpolator will probably be very poor far from this step. This allowance has been added to simplify implementation of search algorithms near the step endpoints.

      Setting the time changes the instance internal state. If a specific state must be preserved, a copy of the instance must be created using StepInterpolator.copy().

      Specified by:
      setInterpolatedTime in interface StepInterpolator
      Parameters:
      time - time of the interpolated point

    • isForward

      public boolean isForward()
      Check if the natural integration direction is forward.

      This method provides the integration direction as specified by the integrator itself, it avoid some nasty problems in degenerated cases like null steps due to cancellation at step initialization, step control or discrete events triggering.

      Specified by:
      isForward in interface StepInterpolator
      Returns:
      true if the integration variable (time) increases during integration

    • getInterpolatedState

      public double[] getInterpolatedState() throws DerivativeException
      Get the state vector of the interpolated point.

      The returned vector is a reference to a reused array, so it should not be modified and it should be copied if it needs to be preserved across several calls.

      Specified by:
      getInterpolatedState in interface StepInterpolator
      Returns:
      state vector at time StepInterpolator.getInterpolatedTime()
      Throws:
      DerivativeException - if user code called from step interpolator finalization triggers one
      See Also:

    • getInterpolatedDerivatives

      public double[] getInterpolatedDerivatives() throws DerivativeException
      Get the derivatives of the state vector of the interpolated point.

      The returned vector is a reference to a reused array, so it should not be modified and it should be copied if it needs to be preserved across several calls.

      Specified by:
      getInterpolatedDerivatives in interface StepInterpolator
      Returns:
      derivatives of the state vector at time StepInterpolator.getInterpolatedTime()
      Throws:
      DerivativeException - if user code called from step interpolator finalization triggers one
      See Also:

    • finalizeStep

      public final void finalizeStep() throws DerivativeException
      Finalize the step.

      Some embedded Runge-Kutta integrators need fewer functions evaluations than their counterpart step interpolators. These interpolators should perform the last evaluations they need by themselves only if they need them. This method triggers these extra evaluations. It can be called directly by the user step handler and it is called automatically if setInterpolatedTime(double) is called.

      Once this method has been called, no other evaluation will be performed on this step. If there is a need to have some side effects between the step handler and the differential equations (for example update some data in the equations once the step has been done), it is advised to call this method explicitly from the step handler before these side effects are set up. If the step handler induces no side effect, then this method can safely be ignored, it will be called transparently as needed.

      Warning: since the step interpolator provided to the step handler as a parameter of the handleStep is valid only for the duration of the handleStep call, one cannot simply store a reference and reuse it later. One should first finalize the instance, then copy this finalized instance into a new object that can be kept.

      This method calls the protected doFinalize method if it has never been called during this step and set a flag indicating that it has been called once. It is the doFinalize method which should perform the evaluations. This wrapping prevents from calling doFinalize several times and hence evaluating the differential equations too often. Therefore, subclasses are not allowed not reimplement it, they should rather reimplement doFinalize.

      Throws:
      DerivativeException - this exception is propagated to the caller if the underlying user function triggers one

    • writeExternal

      public abstract void writeExternal(ObjectOutput out) throws IOException
      Specified by:
      writeExternal in interface Externalizable
      Throws:
      IOException

    • readExternal

      public abstract void readExternal(ObjectInput in) throws IOException, ClassNotFoundException
      Specified by:
      readExternal in interface Externalizable
      Throws:
      IOException
      ClassNotFoundException