/* Resolve the derivative of the current state.
Copyright (c) 1998-2006 The Regents of the University of California.
All rights reserved.
Permission is hereby granted, without written agreement and without
license or royalty fees, to use, copy, modify, and distribute this
software and its documentation for any purpose, provided that the above
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of this software.
IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
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INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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PT_COPYRIGHT_VERSION_2
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*/
package ptolemy.domains.ct.kernel.solver;
import ptolemy.data.DoubleToken;
import ptolemy.domains.ct.kernel.BreakpointODESolver;
import ptolemy.domains.ct.kernel.CTBaseIntegrator;
import ptolemy.domains.ct.kernel.CTDirector;
import ptolemy.domains.ct.kernel.ODESolver;
import ptolemy.kernel.util.IllegalActionException;
import ptolemy.kernel.util.InternalErrorException;
import ptolemy.kernel.util.KernelException;
import ptolemy.kernel.util.Workspace;
//////////////////////////////////////////////////////////////////////////
//// DerivativeResolver
/**
This solver finds the derivatives of the state variables of an ODE
with respect to the current time.
For example, if the ODE is
<pre>
x' = f(x, u, t),
</pre>
the current time is t0, and
<pre>
x(t0) = x0,
</pre>
then this method calculates
<pre>
x'(t0) = f(x(t0), u(t0), t0).
</pre>
<P>
The derivative is obtained by firing the system for one iteration.
This is used for preparing the history for other methods.
Note that time does not progress under this solver.
So, this class implements BreakpointODESolver and can only be
used as a breakpoint solver.
@author Jie Liu, Haiyang Zheng
@version $Id$
@since Ptolemy II 0.4
@Pt.ProposedRating Green (hyzheng)
@Pt.AcceptedRating Green (hyzheng)
*/
public class DerivativeResolver extends ODESolver implements
BreakpointODESolver {
/** Construct a solver in the default workspace with the name
* "CT_Derivative_Resolver". The solver is added to the list of
* objects in the workspace.
* Increment the version number of the workspace.
*/
public DerivativeResolver() {
this(null);
}
/** Construct a solver in the given workspace with the name
* "CT_Derivative_Resolver".
* If the workspace argument is null, use the default workspace.
* The solver is added to the list of objects in the workspace.
* Increment the version number of the workspace.
*
* @param workspace Object for synchronization and version tracking
*/
public DerivativeResolver(Workspace workspace) {
super(workspace);
try {
setName(_DEFAULT_NAME);
} catch (KernelException ex) {
// this should never happen.
throw new InternalErrorException(ex);
}
}
///////////////////////////////////////////////////////////////////
//// public methods ////
/** Fire state transition actors, set converged flag to
* true indicating a fixed-point states have been reached.
* @exception IllegalActionException If thrown in the super class.
*/
public void fireStateTransitionActors() throws IllegalActionException {
super.fireStateTransitionActors();
_setConverged(true);
}
/** Return 0 to indicate that no history information is needed
* by this solver.
* @return 0.
*/
public final int getAmountOfHistoryInformation() {
return 0;
}
/** Return 0 to indicate that the solver needs no auxiliary variable.
* @return 0.
*/
public final int getIntegratorAuxVariableCount() {
return 0;
}
/** Fire the given integrator. Build history information by recording
* the current input as the derivative and using the old state as the
* tentative state. Note that this method is called during the discrete
* phase of execution of an integration. See the _propagateResolvedStates()
* and _discretePhaseExecution() methods in CTMultiSolverDirector class.
* @param integrator The integrator of that calls this method.
* @exception IllegalActionException If can not read input.
*/
public void integratorFire(CTBaseIntegrator integrator)
throws IllegalActionException {
integrator.setTentativeState(integrator.getState());
integrator.setTentativeDerivative(((DoubleToken) integrator.input
.get(0)).doubleValue());
}
/** Return true, since there is no step size control.
* @param integrator The integrator of that calls this method.
* @return True always.
*/
public boolean integratorIsAccurate(CTBaseIntegrator integrator) {
// NOTE: this method is never called because the firing of
// integrators under control of this solver is always accurate.
return true;
}
/** Return the initial step size of the director. Since this solver
* is always used as the breakpoint solver, the next integration
* step will use the initial step size.
* @param integrator The integrator of that calls this method.
* @return The initial step size.
*/
public double integratorPredictedStepSize(CTBaseIntegrator integrator) {
CTDirector director = (CTDirector) getContainer();
return director.getInitialStepSize();
}
///////////////////////////////////////////////////////////////////
//// private variables ////
/** Name of this Solver. */
private static final String _DEFAULT_NAME = "CT_Derivative_Resolver";
}