/** {@inheritDoc} */
public void addEventHandler(
final EventHandler function,
final double maxCheckInterval,
final double convergence,
final int maxIterationCount) {
eventsHandlersManager.addEventHandler(
function, maxCheckInterval,
convergence, maxIterationCount);
}
/**
* Add an event handler for end time checking.
*
* <p>This method can be used to simplify handling of integration end time. It leverages the
* nominal stop condition with the exceptional stop conditions.
*
* @param endTime desired end time
* @param manager manager containing the user-defined handlers
* @return a new manager containing all the user-defined handlers plus a dedicated manager
* triggering a stop event at entTime
*/
protected CombinedEventsManager addEndTimeChecker(
final double startTime, final double endTime, final CombinedEventsManager manager) {
CombinedEventsManager newManager = new CombinedEventsManager();
for (final EventState state : manager.getEventsStates()) {
newManager.addEventHandler(
state.getEventHandler(),
state.getMaxCheckInterval(),
state.getConvergence(),
state.getMaxIterationCount());
}
newManager.addEventHandler(
new EndTimeChecker(endTime),
Double.POSITIVE_INFINITY,
Math.ulp(Math.max(Math.abs(startTime), Math.abs(endTime))),
100);
return newManager;
}
/** {@inheritDoc} */
public Collection<EventHandler> getEventHandlers() {
return eventsHandlersManager.getEventsHandlers();
}
/** {@inheritDoc} */
public void clearEventHandlers() {
eventsHandlersManager.clearEventsHandlers();
}
/** {@inheritDoc} */
@Override
public double integrate(
final FirstOrderDifferentialEquations equations,
final double t0,
final double[] y0,
final double t,
final double[] y)
throws DerivativeException, IntegratorException {
sanityChecks(equations, t0, y0, t, y);
setEquations(equations);
resetEvaluations();
final boolean forward = (t > t0);
// create some internal working arrays
final int stages = c.length + 1;
if (y != y0) {
System.arraycopy(y0, 0, y, 0, y0.length);
}
final double[][] yDotK = new double[stages][y0.length];
final double[] yTmp = new double[y0.length];
// set up an interpolator sharing the integrator arrays
AbstractStepInterpolator interpolator;
if (requiresDenseOutput() || (!eventsHandlersManager.isEmpty())) {
final RungeKuttaStepInterpolator rki = (RungeKuttaStepInterpolator) prototype.copy();
rki.reinitialize(this, yTmp, yDotK, forward);
interpolator = rki;
} else {
interpolator = new DummyStepInterpolator(yTmp, forward);
}
interpolator.storeTime(t0);
// set up integration control objects
stepStart = t0;
double hNew = 0;
boolean firstTime = true;
for (StepHandler handler : stepHandlers) {
handler.reset();
}
CombinedEventsManager manager = addEndTimeChecker(t0, t, eventsHandlersManager);
boolean lastStep = false;
// main integration loop
while (!lastStep) {
interpolator.shift();
double error = 0;
for (boolean loop = true; loop; ) {
if (firstTime || !fsal) {
// first stage
computeDerivatives(stepStart, y, yDotK[0]);
}
if (firstTime) {
final double[] scale;
if (vecAbsoluteTolerance != null) {
scale = vecAbsoluteTolerance;
} else {
scale = new double[y0.length];
Arrays.fill(scale, scalAbsoluteTolerance);
}
hNew =
initializeStep(
equations, forward, getOrder(), scale, stepStart, y, yDotK[0], yTmp, yDotK[1]);
firstTime = false;
}
stepSize = hNew;
// next stages
for (int k = 1; k < stages; ++k) {
for (int j = 0; j < y0.length; ++j) {
double sum = a[k - 1][0] * yDotK[0][j];
for (int l = 1; l < k; ++l) {
sum += a[k - 1][l] * yDotK[l][j];
}
yTmp[j] = y[j] + stepSize * sum;
}
computeDerivatives(stepStart + c[k - 1] * stepSize, yTmp, yDotK[k]);
}
// estimate the state at the end of the step
for (int j = 0; j < y0.length; ++j) {
double sum = b[0] * yDotK[0][j];
for (int l = 1; l < stages; ++l) {
sum += b[l] * yDotK[l][j];
}
yTmp[j] = y[j] + stepSize * sum;
}
// estimate the error at the end of the step
error = estimateError(yDotK, y, yTmp, stepSize);
if (error <= 1.0) {
// discrete events handling
interpolator.storeTime(stepStart + stepSize);
if (manager.evaluateStep(interpolator)) {
final double dt = manager.getEventTime() - stepStart;
if (Math.abs(dt) <= Math.ulp(stepStart)) {
// rejecting the step would lead to a too small next step, we accept it
loop = false;
} else {
// reject the step to match exactly the next switch time
hNew = dt;
}
} else {
// accept the step
loop = false;
}
} else {
// reject the step and attempt to reduce error by stepsize control
final double factor =
Math.min(maxGrowth, Math.max(minReduction, safety * Math.pow(error, exp)));
hNew = filterStep(stepSize * factor, forward, false);
}
}
// the step has been accepted
final double nextStep = stepStart + stepSize;
System.arraycopy(yTmp, 0, y, 0, y0.length);
manager.stepAccepted(nextStep, y);
lastStep = manager.stop();
// provide the step data to the step handler
interpolator.storeTime(nextStep);
for (StepHandler handler : stepHandlers) {
handler.handleStep(interpolator, lastStep);
}
stepStart = nextStep;
if (fsal) {
// save the last evaluation for the next step
System.arraycopy(yDotK[stages - 1], 0, yDotK[0], 0, y0.length);
}
if (manager.reset(stepStart, y) && !lastStep) {
// some event handler has triggered changes that
// invalidate the derivatives, we need to recompute them
computeDerivatives(stepStart, y, yDotK[0]);
}
if (!lastStep) {
// in some rare cases we may get here with stepSize = 0, for example
// when an event occurs at integration start, reducing the first step
// to zero; we have to reset the step to some safe non zero value
stepSize = filterStep(stepSize, forward, true);
// stepsize control for next step
final double factor =
Math.min(maxGrowth, Math.max(minReduction, safety * Math.pow(error, exp)));
final double scaledH = stepSize * factor;
final double nextT = stepStart + scaledH;
final boolean nextIsLast = forward ? (nextT >= t) : (nextT <= t);
hNew = filterStep(scaledH, forward, nextIsLast);
}
}
final double stopTime = stepStart;
resetInternalState();
return stopTime;
}
