Examples of org.apache.commons.math.ode.EulerStepInterpolator

org.apache.commons.math.ode.EulerStepInterpolator
This class implements a linear interpolator for step.
This interpolator allow to compute dense output inside the last step computed. The interpolation equation is consistent with the integration scheme :
```
 y(t_n + theta h) = y (t_n + h) - (1-theta) h y' 
```
where theta belongs to [0 ; 1] and where y' is the evaluation of the derivatives already computed during the step.
@see EulerIntegrator @version $Revision: 620312 $ $Date: 2008-02-10 12:28:59 -0700 (Sun, 10 Feb 2008) $ @since 1.2


  public void testNoReset() {


    double[]   y    =   { 0.0, 1.0, -2.0 };
    double[][] yDot = { { 1.0, 2.0, -2.0 } };
    EulerStepInterpolator interpolator = new EulerStepInterpolator();
    interpolator.reinitialize(new DummyEquations(), y, yDot, true);
    interpolator.storeTime(0);
    interpolator.shift();
    interpolator.storeTime(1);


    double[] result = interpolator.getInterpolatedState();
    for (int i = 0; i < result.length; ++i) {
      assertTrue(Math.abs(result[i] - y[i]) < 1.0e-10);
    }


  }

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    double   t0 = 0;
    double[] y0 = {0.0, 1.0, -2.0};


    double[] y = (double[]) y0.clone();
    double[][] yDot = { new double[y0.length] };
    EulerStepInterpolator interpolator = new EulerStepInterpolator();
    interpolator.reinitialize(new DummyEquations(), y, yDot, true);
    interpolator.storeTime(t0);


    double dt = 1.0;
    y[0] =  1.0;
    y[1] =  3.0;
    y[2] = -4.0;
    yDot[0][0] = (y[0] - y0[0]) / dt;
    yDot[0][1] = (y[1] - y0[1]) / dt;
    yDot[0][2] = (y[2] - y0[2]) / dt;
    interpolator.shift();
    interpolator.storeTime(t0 + dt);


    interpolator.setInterpolatedTime(interpolator.getPreviousTime());
    double[] result = interpolator.getInterpolatedState();
    for (int i = 0; i < result.length; ++i) {
      assertTrue(Math.abs(result[i] - y0[i]) < 1.0e-10);
    }


    interpolator.setInterpolatedTime(interpolator.getCurrentTime());
    result = interpolator.getInterpolatedState();
    for (int i = 0; i < result.length; ++i) {
      assertTrue(Math.abs(result[i] - y[i]) < 1.0e-10);
    }


  }

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  public void testInterpolationInside()
    throws DerivativeException {


    double[]   y    =   { 1.0, 3.0, -4.0 };
    double[][] yDot = { { 1.0, 2.0, -2.0 } };
    EulerStepInterpolator interpolator = new EulerStepInterpolator();
    interpolator.reinitialize(new DummyEquations(), y, yDot, true);
    interpolator.storeTime(0);
    interpolator.shift();
    interpolator.storeTime(1);


    interpolator.setInterpolatedTime(0.1);
    double[] result = interpolator.getInterpolatedState();
    assertTrue(Math.abs(result[0] - 0.1) < 1.0e-10);
    assertTrue(Math.abs(result[1] - 1.2) < 1.0e-10);
    assertTrue(Math.abs(result[2] + 2.2) < 1.0e-10);


    interpolator.setInterpolatedTime(0.5);
    result = interpolator.getInterpolatedState();
    assertTrue(Math.abs(result[0] - 0.5) < 1.0e-10);
    assertTrue(Math.abs(result[1] - 2.0) < 1.0e-10);
    assertTrue(Math.abs(result[2] + 3.0) < 1.0e-10);


  }

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Related Classes of org.apache.commons.math.ode.EulerStepInterpolator

org.apache.commons.math.ode.EulerStepInterpolatorTest

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