Examples of org.apache.commons.math3.ode.FirstOrderIntegrator.integrate()

Class org.apache.commons.math3.ode.FirstOrderIntegrator

Examples of org.apache.commons.math3.ode.FirstOrderIntegrator.integrate()

org.apache.commons.math3.ode.FirstOrderIntegrator.integrate()
Integrate the differential equations up to the given time.
This method solves an Initial Value Problem (IVP).

Since this method stores some internal state variables made available in its public interface during integration ( {@link #getCurrentSignedStepsize()}), it is not thread-safe.
@param equations differential equations to integrate @param t0 initial time @param y0 initial value of the state vector at t0 @param t target time for the integration(can be set to a value smaller than t0 for backward integration) @param y placeholder where to put the state vector at each successfulstep (and hence at the end of integration), can be the same object as y0 @return stop time, will be the same as target time if integration reached itstarget, but may be different if some {@link org.apache.commons.math3.ode.events.EventHandler} stops it at some point. @exception DimensionMismatchException if arrays dimension do not match equations settings @exception NumberIsTooSmallException if integration step is too small @exception MaxCountExceededException if the number of functions evaluations is exceeded @exception NoBracketingException if the location of an event cannot be bracketed

      FirstOrderIntegrator integ = new DormandPrince853Integrator(minStep, maxStep,
                                                                  scalAbsoluteTolerance,
                                                                  scalRelativeTolerance);
      TestProblemHandler handler = new TestProblemHandler(pb, integ);
      integ.addStepHandler(handler);
      integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(),
                      pb.getFinalTime(), new double[pb.getDimension()]);


      Assert.assertTrue(handler.getLastError() < 1.1e-7);
      Assert.assertTrue(handler.getMaximalValueError() < 1.1e-7);
      Assert.assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);

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    double convergence = 1.0e-8 * maxStep;
    for (int l = 0; l < functions.length; ++l) {
      integ.addEventHandler(functions[l], Double.POSITIVE_INFINITY, convergence, 1000);
    }
    Assert.assertEquals(functions.length, integ.getEventHandlers().size());
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);


    Assert.assertEquals(0, handler.getMaximalValueError(), 2.1e-7);
    Assert.assertEquals(0, handler.getMaximalTimeError(), convergence);

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    FirstOrderIntegrator integ = new DormandPrince853Integrator(minStep, maxStep,
                                                                scalAbsoluteTolerance,
                                                                scalRelativeTolerance);
    integ.addStepHandler(new KeplerHandler(pb));
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);


    Assert.assertEquals(integ.getEvaluations(), pb.getCalls());
    Assert.assertTrue(pb.getCalls() < 3300);

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    FirstOrderIntegrator integ = new DormandPrince853Integrator(minStep, maxStep,
                                                               scalAbsoluteTolerance,
                                                               scalRelativeTolerance);
    integ.addStepHandler(new VariableHandler());
    double stopTime = integ.integrate(pb,
                                      pb.getInitialTime(), pb.getInitialState(),
                                      pb.getFinalTime(), new double[pb.getDimension()]);
    Assert.assertEquals(pb.getFinalTime(), stopTime, 1.0e-10);
    Assert.assertEquals("Dormand-Prince 8 (5, 3)", integ.getName());
  }

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    final StepProblem stepProblem = new StepProblem(0.0, 1.0, 2.0);
    FirstOrderIntegrator integ =
      new DormandPrince853Integrator(0.1, 10, 1.0e-12, 0.0);
    integ.addEventHandler(stepProblem, 1.0, 1.0e-12, 1000);
    double[] y = { Double.NaN };
    integ.integrate(stepProblem, 0.0, new double[] { 0.0 }, 10.0, y);
    Assert.assertEquals(8.0, y[0], 1.0e-12);
  }


  private static class KeplerHandler implements StepHandler {
    public KeplerHandler(TestProblem3 pb) {

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          double[] y = interpolator.getInterpolatedState();
          System.out.println("->" + t + " " + y[0] + " " + y[1]);
        }
      };
      integrator.addStepHandler(stepHandler);
      integrator.integrate(ode, 0.0, y, 16.0, y); // now y contains final state
                                                  // at time
                                                  // t=16.0
    }
  }

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        integ.addStepHandler(new StepNormalizer(0.5, this, mode, bounds));
        double[] y   = {0.0};
        double start = reverse ? getEnd()   : getStart();
        double end   = reverse ? getStart() : getEnd();
        output       = new ArrayList<Double>();
        integ.integrate(this, start, y, end, y);
        double[] actual = new double[output.size()];
        for(int i = 0; i < actual.length; i++) {
            actual[i] = output.get(i);
        }
        assertArrayEquals(expected, actual, 1e-5);

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        EventHandler[] functions = pb.getEventsHandlers();
        for (int l = 0; l < functions.length; ++l) {
          integ.addEventHandler(functions[l],
                                     Double.POSITIVE_INFINITY, 1.0e-6 * step, 1000);
        }
        double stopTime = integ.integrate(pb,
                                          pb.getInitialTime(), pb.getInitialState(),
                                          pb.getFinalTime(), new double[pb.getDimension()]);
        if (functions.length == 0) {
            Assert.assertEquals(pb.getFinalTime(), stopTime, 1.0e-10);
        }

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    double step = (pb.getFinalTime() - pb.getInitialTime()) * 0.001;


    FirstOrderIntegrator integ = new MidpointIntegrator(step);
    TestProblemHandler handler = new TestProblemHandler(pb, integ);
    integ.addStepHandler(handler);
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);


    Assert.assertTrue(handler.getLastError() < 2.0e-7);
    Assert.assertTrue(handler.getMaximalValueError() < 1.0e-6);

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    double step = (pb.getFinalTime() - pb.getInitialTime()) * 0.2;


    FirstOrderIntegrator integ = new MidpointIntegrator(step);
    TestProblemHandler handler = new TestProblemHandler(pb, integ);
    integ.addStepHandler(handler);
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);


    Assert.assertTrue(handler.getLastError() > 0.01);
    Assert.assertTrue(handler.getMaximalValueError() > 0.05);

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