Drake
SystemBase Class Referenceabstract

## Detailed Description

Provides non-templatized functionality shared by the templatized System classes.

Terminology: in general a Drake System is a tree structure composed of "subsystems", which are themselves System objects. The corresponding Context is a parallel tree structure composed of "subcontexts", which are themselves Context objects. There is a one-to-one correspondence between subsystems and subcontexts. Within a given System (Context), its child subsystems (subcontexts) are indexed using a SubsystemIndex; there is no separate SubcontextIndex since the numbering must be identical.

#include <drake/systems/framework/system_base.h>

## Classes

struct  ContextSizes
Return type for get_context_sizes(). More...

## Public Member Functions

~SystemBase () override

void set_name (const std::string &name)
Sets the name of the system. More...

const std::string & get_name () const
Returns the name last supplied to set_name(), if any. More...

const std::string & GetSystemName () const final
Returns a human-readable name for this system, for use in messages and logging. More...

std::string GetSystemPathname () const final
Generates and returns a human-readable full path name of this subsystem, for use in messages and logging. More...

std::string GetSystemType () const final
Returns the most-derived type of this concrete System object as a human-readable string suitable for use in error messages. More...

std::unique_ptr< ContextBaseAllocateContext () const
Returns a Context suitable for use with this System. More...

int num_input_ports () const
Returns the number of input ports currently allocated in this System. More...

int num_output_ports () const
Returns the number of output ports currently allocated in this System. More...

const InputPortBaseget_input_port_base (InputPortIndex port_index) const
Returns a reference to an InputPort given its port_index. More...

const OutputPortBaseget_output_port_base (OutputPortIndex port_index) const
Returns a reference to an OutputPort given its port_index. More...

int num_total_inputs () const
Returns the total dimension of all of the vector-valued input ports (as if they were muxed). More...

int num_total_outputs () const
Returns the total dimension of all of the vector-valued output ports (as if they were muxed). More...

virtual std::multimap< int, intGetDirectFeedthroughs () const =0
Reports all direct feedthroughs from input ports to output ports. More...

int num_cache_entries () const
Returns the number nc of cache entries currently allocated in this System. More...

const CacheEntryget_cache_entry (CacheIndex index) const
Returns a reference to a CacheEntry given its index. More...

CacheEntryget_mutable_cache_entry (CacheIndex index)
(Advanced) Returns a mutable reference to a CacheEntry given its index. More...

int num_continuous_states () const
Returns the number of declared continuous state variables. More...

int num_discrete_state_groups () const
Returns the number of declared discrete state groups (each group is a vector-valued discrete state variable). More...

int num_abstract_states () const
Returns the number of declared abstract state variables. More...

int num_numeric_parameter_groups () const
Returns the number of declared numeric parameters (each of these is a vector-valued parameter). More...

int num_abstract_parameters () const
Returns the number of declared abstract parameters. More...

int implicit_time_derivatives_residual_size () const
Returns the size of the implicit time derivatives residual vector. More...

void ValidateContext (const ContextBase &context) const final
Checks whether the given context was created for this system. More...

void ValidateContext (const ContextBase *context) const
Checks whether the given context was created for this system. More...

template<class Clazz >
void ValidateCreatedForThisSystem (const Clazz &object) const
Checks whether the given object was created for this system. More...

Does not allow copy, move, or assignment
SystemBase (const SystemBase &)=delete

SystemBaseoperator= (const SystemBase &)=delete

SystemBase (SystemBase &&)=delete

SystemBaseoperator= (SystemBase &&)=delete

Input port evaluation

These methods provide scalar type-independent evaluation of a System input port in a particular Context.

If necessary, they first cause the port's value to become up to date, then they return a reference to the now-up-to-date value in the given Context.

Specified preconditions for these methods operate as follows: The preconditions will be checked in Debug builds but some or all might not be checked in Release builds for performance reasons. If we do check, and a precondition is violated, an std::logic_error will be thrown with a helpful message.

System::EvalVectorInput(), System::EvalEigenVectorInput() for scalar type-specific input port access.
const AbstractValueEvalAbstractInput (const ContextBase &context, int port_index) const
Returns the value of the input port with the given port_index as an AbstractValue, which is permitted for ports of any type. More...

template<typename V >
const V * EvalInputValue (const ContextBase &context, int port_index) const
Returns the value of an abstract-valued input port with the given port_index as a value of known type V. More...

## Protected Member Functions

SystemBase ()=default
(Internal use only). More...

void AddInputPort (std::unique_ptr< InputPortBase > port)
(Internal use only) Adds an already-constructed input port to this System. More...

void AddOutputPort (std::unique_ptr< OutputPortBase > port)
(Internal use only) Adds an already-constructed output port to this System. More...

std::string NextInputPortName (std::variant< std::string, UseDefaultName > given_name) const
(Internal use only) Returns a name for the next input port, using the given name if it isn't kUseDefaultName, otherwise making up a name like "u3" from the next available input port index. More...

std::string NextOutputPortName (std::variant< std::string, UseDefaultName > given_name) const
(Internal use only) Returns a name for the next output port, using the given name if it isn't kUseDefaultName, otherwise making up a name like "y3" from the next available output port index. More...

(Internal use only) Assigns a ticket to a new discrete variable group with the given index. More...

(Internal use only) Assigns a ticket to a new abstract state variable with the given index. More...

(Internal use only) Assigns a ticket to a new numeric parameter with the given index. More...

(Internal use only) Assigns a ticket to a new abstract parameter with the given index. More...

CacheEntryDeclareCacheEntryWithKnownTicket (DependencyTicket known_ticket, std::string description, ValueProducer value_producer, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()})
(Internal use only) This is for cache entries associated with pre-defined tickets, for example the cache entry for time derivatives. More...

const internal::SystemParentServiceInterface * get_parent_service () const
Returns a pointer to the service interface of the immediately enclosing Diagram if one has been set, otherwise nullptr. More...

DependencyTicket assign_next_dependency_ticket ()
(Internal use only) Assigns the next unused dependency ticket number, unique only within a particular system. More...

virtual std::function< void(const AbstractValue &)> MakeFixInputPortTypeChecker (InputPortIndex port_index) const =0
(Internal use only) Given a port_index, returns a function to be called when validating Context::FixInputPort requests. More...

const AbstractValueEvalAbstractInputImpl (const char *func, const ContextBase &context, InputPortIndex port_index) const
(Internal use only) Shared code for updating an input port and returning a pointer to its abstract value, or nullptr if the port is not connected. More...

void ThrowNegativePortIndex (const char *func, int port_index) const
Throws std::exception to report a negative port_index that was passed to API method func. More...

void ThrowInputPortIndexOutOfRange (const char *func, InputPortIndex port_index) const
Throws std::exception to report bad input port_index that was passed to API method func. More...

void ThrowOutputPortIndexOutOfRange (const char *func, OutputPortIndex port_index) const
Throws std::exception to report bad output port_index that was passed to API method func. More...

void ThrowNotAVectorInputPort (const char *func, InputPortIndex port_index) const
Throws std::exception because someone misused API method func, that is only allowed for declared-vector input ports, on an abstract port whose index is given here. More...

void ThrowInputPortHasWrongType (const char *func, InputPortIndex port_index, const std::string &expected_type, const std::string &actual_type) const
Throws std::exception because someone called API method func claiming the input port had some value type that was wrong. More...

void ThrowCantEvaluateInputPort (const char *func, InputPortIndex port_index) const
Throws std::exception because someone called API method func, that requires this input port to be evaluatable, but the port was neither fixed nor connected. More...

const InputPortBaseGetInputPortBaseOrThrow (const char *func, int port_index) const
(Internal use only) Returns the InputPortBase at index port_index, throwing std::exception we don't like the port index. More...

const OutputPortBaseGetOutputPortBaseOrThrow (const char *func, int port_index) const
(Internal use only) Returns the OutputPortBase at index port_index, throwing std::exception if we don't like the port index. More...

void ThrowValidateContextMismatch (const ContextBase &) const
(Internal use only) Throws std::exception with a message that the sanity check(s) given by ValidateContext have failed. More...

void InitializeContextBase (ContextBase *context) const
This method must be invoked from within derived class DoAllocateContext() implementations right after the concrete Context object has been allocated. More...

virtual std::unique_ptr< ContextBaseDoAllocateContext () const =0
Derived class implementations should allocate a suitable concrete Context type, then invoke the above InitializeContextBase() method. More...

const ContextSizesget_context_sizes () const
Obtains access to the declared Context partition sizes as accumulated during LeafSystem or Diagram construction . More...

ContextSizesget_mutable_context_sizes ()

void set_implicit_time_derivatives_residual_size (int n)
Allows a LeafSystem to override the default size for the implicit time derivatives residual and a Diagram to sum up the total size. More...

internal::SystemId get_system_id () const
(Internal) Gets the id used to tag context data as being created by this system. More...

## Static Protected Member Functions

static void set_parent_service (SystemBase *child, const internal::SystemParentServiceInterface *parent_service)
(Internal use only) Declares that parent_service is the service interface of the Diagram that owns this subsystem. More...

static void ThrowInputPortHasWrongType (const char *func, const std::string &system_pathname, InputPortIndex, const std::string &port_name, const std::string &expected_type, const std::string &actual_type)
Throws std::exception because someone called API method func claiming the input port had some value type that was wrong. More...

static void ThrowUnsupportedScalarConversion (const SystemBase &from, const std::string &destination_type_name)
(Internal use only) Throws a std::exception for unsupported scalar type conversions. More...

static const ContextSizesget_context_sizes (const SystemBase &system)
Allows Diagram to access protected get_context_sizes() recursively on its subsystems. More...

## Declare cache entries

Methods in this section are used by derived classes to declare cache entries for their own internal computations. (Other cache entries are provided automatically for well-known computations such as output ports and time derivatives.) Cache entries may contain values of any type, however the type for any particular cache entry is fixed after first allocation. Every cache entry must have an allocator function Allocate() and a calculator function Calc(). Allocate() returns an object suitable for holding a value of the cache entry. Calc() uses the contents of a given Context to produce the cache entry's value, which is placed in an object of the type returned by Allocate().

Warning
These methods are currently specified as public access, but will be demoted to protected access on or after 2021-10-01.

#### Prerequisites

Correct runtime caching behavior depends critically on understanding the dependencies of the cache entry's Calc() function (we call those "prerequisites"). If none of the prerequisites has changed since the last time Calc() was invoked to set the cache entry's value, then we don't need to perform a potentially expensive recalculation. On the other hand, if any of the prerequisites has changed then the current value is invalid and must not be used without first recomputing.

Currently it is not possible for Drake to infer prerequisites accurately and automatically from inspection of the Calc() implementation. Therefore, if you don't say otherwise, Drake will assume Calc() is dependent on all value sources in the Context, including time, state, input ports, parameters, and accuracy. That means the cache entry's value will be considered invalid if any of those sources has changed since the last time the value was calculated. That is safe, but can result in more computation than necessary. If you know that your Calc() method has fewer prerequisites, you may say so by providing an explicit list in the prerequisites_of_calc parameter. Every possible prerequisite has a DependencyTicket ("ticket"), and the list should consist of tickets. For example, if your calculator depends only on time (e.g. Calc(context) is sin(context.get_time())) then you would specify prerequisites_of_calc={time_ticket()} here. See Dependency tickets for a list of the possible tickets and what they mean.

Warning
It is critical that the prerequisite list you supply be accurate, or at least conservative, for correct functioning of the caching system. Drake cannot currently detect that a Calc() function accesses an undeclared prerequisite. Even assuming you have correctly listed the prerequisites, you should include a prominent comment in every Calc() implementation noting that if the implementation is changed then the prerequisite list must be updated correspondingly.

A technique you can use to ensure that prerequisites have been properly specified is to make use of the Context's DisableCaching() method, which causes cache values to be recalculated unconditionally. You should get identical results with caching enabled or disabled, with speed being the only difference. You can also disable caching for individual cache entries in a Context, or specify that individual cache entries should be disabled by default when they are first allocated.

ContextBase::DisableCaching()
CacheEntry::disable_caching()
CacheEntry::disable_caching_by_default()
LeafOutputPort::disable_caching_by_default()

#### Which signature to use?

Although the allocator and calculator functions ultimately satisfy generic function signatures defined by a ValueProducer, we provide a variety of DeclareCacheEntry() signatures here for convenient specification, with mapping to the generic form handled invisibly. In particular, allocators are most easily defined by providing a model value that can be used to construct an allocator that copies the model when a new value object is needed. Alternatively a method can be provided that constructs a value object when invoked (those methods are conventionally, but not necessarily, named MakeSomething() where Something is replaced by the cache entry value type).

Because cache entry values are ultimately stored in AbstractValue objects, the underlying types must be suitable. That means the type must be copy constructible or cloneable. For methods below that are not given an explicit model value or construction ("make") method, the underlying type must also be default constructible.

drake::Value for more about abstract values.
CacheEntryDeclareCacheEntry (std::string description, std::function< std::unique_ptr< AbstractValue >()> alloc_function, std::function< void(const ContextBase &, AbstractValue *)> calc_function, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()})
(Deprecated.) More...

template<class MySystem , class MyContext , typename ValueType >
CacheEntryDeclareCacheEntry (std::string description, ValueType(MySystem::*make)() const, void(MySystem::*calc)(const MyContext &, ValueType *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()})
(Deprecated.) More...

template<class MySystem , class MyContext , typename ValueType >
CacheEntryDeclareCacheEntry (std::string description, const ValueType &model_value, void(MySystem::*calc)(const MyContext &, ValueType *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()})
Declares a cache entry by specifying a model value of concrete type ValueType and a calculator function that is a class member function (method) with signature: More...

template<class MySystem , class MyContext , typename ValueType >
CacheEntryDeclareCacheEntry (std::string description, const ValueType &model_value, ValueType(MySystem::*calc)(const MyContext &) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()})
(Deprecated.) More...

template<class MySystem , class MyContext , typename ValueType >
CacheEntryDeclareCacheEntry (std::string description, void(MySystem::*calc)(const MyContext &, ValueType *) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()})
Declares a cache entry by specifying only a calculator function that is a class member function (method) with signature: More...

template<class MySystem , class MyContext , typename ValueType >
CacheEntryDeclareCacheEntry (std::string description, ValueType(MySystem::*calc)(const MyContext &) const, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()})
(Deprecated.) More...

CacheEntryDeclareCacheEntry (std::string description, ValueProducer value_producer, std::set< DependencyTicket > prerequisites_of_calc={ all_sources_ticket()})
Declares a new CacheEntry in this System using the most generic form of the calculation function. More...

## Dependency tickets

Use these tickets to declare well-known sources as prerequisites of a downstream computation such as an output port, derivative, update, or cache entry. The ticket numbers for the built-in sources are the same for all systems. For time and accuracy they refer to the same global resource; otherwise they refer to the specified sources within the referencing system.

A dependency ticket for a more specific resource (a particular input or output port, a discrete variable group, abstract state variable, a parameter, or a cache entry) is allocated and stored with the resource when it is declared. Usually the tickets are obtained directly from the resource but you can recover them with methods here knowing only the resource index.

DependencyTicket discrete_state_ticket (DiscreteStateIndex index) const
Returns a ticket indicating dependence on a particular discrete state variable xdᵢ (may be a vector). More...

DependencyTicket abstract_state_ticket (AbstractStateIndex index) const
Returns a ticket indicating dependence on a particular abstract state variable xaᵢ. More...

DependencyTicket numeric_parameter_ticket (NumericParameterIndex index) const
Returns a ticket indicating dependence on a particular numeric parameter pnᵢ (may be a vector). More...

DependencyTicket abstract_parameter_ticket (AbstractParameterIndex index) const
Returns a ticket indicating dependence on a particular abstract parameter paᵢ. More...

DependencyTicket input_port_ticket (InputPortIndex index) const
Returns a ticket indicating dependence on input port uᵢ indicated by index. More...

DependencyTicket cache_entry_ticket (CacheIndex index) const
Returns a ticket indicating dependence on the cache entry indicated by index. More...

DependencyTicket output_port_ticket (OutputPortIndex index) const
(Internal use only) Returns a ticket indicating dependence on the output port indicated by index. More...

static DependencyTicket nothing_ticket ()
Returns a ticket indicating that a computation does not depend on any source value; that is, it is a constant. More...

static DependencyTicket time_ticket ()
Returns a ticket indicating dependence on time. More...

static DependencyTicket accuracy_ticket ()
Returns a ticket indicating dependence on the accuracy setting in the Context. More...

static DependencyTicket q_ticket ()
Returns a ticket indicating that a computation depends on configuration state variables q. More...

static DependencyTicket v_ticket ()
Returns a ticket indicating dependence on velocity state variables v. More...

static DependencyTicket z_ticket ()
Returns a ticket indicating dependence on any or all of the miscellaneous continuous state variables z. More...

static DependencyTicket xc_ticket ()
Returns a ticket indicating dependence on all of the continuous state variables q, v, or z. More...

static DependencyTicket xd_ticket ()
Returns a ticket indicating dependence on all of the numerical discrete state variables, in any discrete variable group. More...

static DependencyTicket xa_ticket ()
Returns a ticket indicating dependence on all of the abstract state variables in the current Context. More...

static DependencyTicket all_state_ticket ()
Returns a ticket indicating dependence on all state variables x in this system, including continuous variables xc, discrete (numeric) variables xd, and abstract state variables xa. More...

static DependencyTicket pn_ticket ()
Returns a ticket indicating dependence on all of the numerical parameters in the current Context. More...

static DependencyTicket pa_ticket ()
Returns a ticket indicating dependence on all of the abstract parameters pa in the current Context. More...

static DependencyTicket all_parameters_ticket ()
Returns a ticket indicating dependence on all parameters p in this system, including numeric parameters pn, and abstract parameters pa. More...

static DependencyTicket all_input_ports_ticket ()
Returns a ticket indicating dependence on all input ports u of this system. More...

static DependencyTicket all_sources_except_input_ports_ticket ()
Returns a ticket indicating dependence on every possible independent source value except input ports. More...

static DependencyTicket all_sources_ticket ()
Returns a ticket indicating dependence on every possible independent source value, including time, accuracy, state, input ports, and parameters (but not cache entries). More...

static DependencyTicket configuration_ticket ()
Returns a ticket indicating dependence on all source values that may affect configuration-dependent computations. More...

static DependencyTicket kinematics_ticket ()
Returns a ticket indicating dependence on all source values that may affect configuration- or velocity-dependent computations. More...

static DependencyTicket xcdot_ticket ()
Returns a ticket for the cache entry that holds time derivatives of the continuous variables. More...

static DependencyTicket pe_ticket ()
Returns a ticket for the cache entry that holds the potential energy calculation. More...

static DependencyTicket ke_ticket ()
Returns a ticket for the cache entry that holds the kinetic energy calculation. More...

static DependencyTicket pc_ticket ()
Returns a ticket for the cache entry that holds the conservative power calculation. More...

static DependencyTicket pnc_ticket ()
Returns a ticket for the cache entry that holds the non-conservative power calculation. More...

## ◆ SystemBase() [1/3]

 SystemBase ( const SystemBase & )
delete

## ◆ SystemBase() [2/3]

 SystemBase ( SystemBase && )
delete

## ◆ ~SystemBase()

 ~SystemBase ( )
override

## ◆ SystemBase() [3/3]

 SystemBase ( )
protecteddefault

(Internal use only).

## ◆ abstract_parameter_ticket()

 DependencyTicket abstract_parameter_ticket ( AbstractParameterIndex index ) const

Returns a ticket indicating dependence on a particular abstract parameter paᵢ.

pa_ticket() to obtain a ticket for all abstract parameters.

## ◆ abstract_state_ticket()

 DependencyTicket abstract_state_ticket ( AbstractStateIndex index ) const

Returns a ticket indicating dependence on a particular abstract state variable xaᵢ.

xa_ticket() to obtain a ticket for all abstract variables.

## ◆ accuracy_ticket()

 static DependencyTicket accuracy_ticket ( )
static

Returns a ticket indicating dependence on the accuracy setting in the Context.

This is the same ticket for all systems and refers to the same accuracy value.

 void AddAbstractParameter ( AbstractParameterIndex index )
protected

(Internal use only) Assigns a ticket to a new abstract parameter with the given index.

Precondition
The supplied index must be the next available one; that is, indexes must be assigned sequentially.

 void AddAbstractState ( AbstractStateIndex index )
protected

(Internal use only) Assigns a ticket to a new abstract state variable with the given index.

Precondition
The supplied index must be the next available one; that is, indexes must be assigned sequentially.

 void AddDiscreteStateGroup ( DiscreteStateIndex index )
protected

(Internal use only) Assigns a ticket to a new discrete variable group with the given index.

Precondition
The supplied index must be the next available one; that is, indexes must be assigned sequentially.

 void AddInputPort ( std::unique_ptr< InputPortBase > port )
protected

Insists that the port already contains a reference to this System, and that the port's index is already set to the next available input port index for this System, that the port name is unique (just within this System), and that the port name is non-empty.

 void AddNumericParameter ( NumericParameterIndex index )
protected

(Internal use only) Assigns a ticket to a new numeric parameter with the given index.

Precondition
The supplied index must be the next available one; that is, indexes must be assigned sequentially.

 void AddOutputPort ( std::unique_ptr< OutputPortBase > port )
protected

Insists that the port already contains a reference to this System, and that the port's index is already set to the next available output port index for this System, and that the name of the port is unique.

Exceptions
 std::exception if the name of the output port is not unique.

## ◆ all_input_ports_ticket()

 static DependencyTicket all_input_ports_ticket ( )
static

Returns a ticket indicating dependence on all input ports u of this system.

input_port_ticket() to obtain a ticket for just one input port.

## ◆ all_parameters_ticket()

 static DependencyTicket all_parameters_ticket ( )
static

Returns a ticket indicating dependence on all parameters p in this system, including numeric parameters pn, and abstract parameters pa.

## ◆ all_sources_except_input_ports_ticket()

 static DependencyTicket all_sources_except_input_ports_ticket ( )
static

Returns a ticket indicating dependence on every possible independent source value except input ports.

This can be helpful in avoiding the incorrect appearance of algebraic loops in a Diagram (those always involve apparent input port dependencies). For an output port, use this ticket plus tickets for just the input ports on which the output computation actually depends. The sources included in this ticket are: time, accuracy, state, and parameters. Note that dependencies on cache entries are not included here. Usually that won't matter since cache entries typically depend on at least one of time, accuracy, state, or parameters so will be invalidated for the same reason the current computation is. However, for a computation that depends on a cache entry that depends only on input ports, be sure that you have included those input ports in the dependency list, or include a direct dependency on the cache entry.

input_port_ticket() to obtain a ticket for an input port.
cache_entry_ticket() to obtain a ticket for a cache entry.
all_sources_ticket() to also include all input ports as dependencies.

## ◆ all_sources_ticket()

 static DependencyTicket all_sources_ticket ( )
static

Returns a ticket indicating dependence on every possible independent source value, including time, accuracy, state, input ports, and parameters (but not cache entries).

This is the default dependency for computations that have not specified anything more refined. It is equivalent to the set {all_sources_except_input_ports_ticket(), all_input_ports_ticket()}.

cache_entry_ticket() to obtain a ticket for a cache entry.

## ◆ all_state_ticket()

 static DependencyTicket all_state_ticket ( )
static

Returns a ticket indicating dependence on all state variables x in this system, including continuous variables xc, discrete (numeric) variables xd, and abstract state variables xa.

This does not imply dependence on time, accuracy, parameters, or inputs; those must be specified separately. If you mean to express dependence on all possible value sources, use all_sources_ticket() instead.

## ◆ AllocateContext()

 std::unique_ptr AllocateContext ( ) const

Returns a Context suitable for use with this System.

Context resources are allocated based on resource requests that were made during System construction.

## ◆ assign_next_dependency_ticket()

 DependencyTicket assign_next_dependency_ticket ( )
protected

(Internal use only) Assigns the next unused dependency ticket number, unique only within a particular system.

Each call to this method increments the ticket number.

## ◆ cache_entry_ticket()

 DependencyTicket cache_entry_ticket ( CacheIndex index ) const

Returns a ticket indicating dependence on the cache entry indicated by index.

Note that cache entries are not included in the all_sources ticket so must be listed separately.

Precondition
index selects an existing cache entry in this System.

## ◆ configuration_ticket()

 static DependencyTicket configuration_ticket ( )
static

Returns a ticket indicating dependence on all source values that may affect configuration-dependent computations.

In particular, this category does not include time, generalized velocities v, miscellaneous continuous state variables z, or input ports. Generalized coordinates q are included, as well as any discrete state variables that have been declared as configuration variables, and configuration-affecting parameters. Finally we assume that the accuracy setting may affect some configuration-dependent computations. Examples: a parameter that affects length may change the computation of an end-effector location. A change in accuracy requirement may require recomputation of an iterative approximation of contact forces.

kinematics_ticket()
Note
Currently there is no way to declare specific variables and parameters to be configuration-affecting so we include all state variables and parameters except for state variables v and z.

## ◆ DeclareCacheEntry() [1/7]

 CacheEntry& DeclareCacheEntry ( std::string description, ValueProducer value_producer, std::set< DependencyTicket > prerequisites_of_calc = { all_sources_ticket()} )
protected

Declares a new CacheEntry in this System using the most generic form of the calculation function.

Prefer one of the more convenient signatures below if you can. The new cache entry is assigned a unique CacheIndex and DependencyTicket, which can be obtained from the returned CacheEntry.

Parameters
 [in] description A human-readable description of this cache entry, most useful for debugging and documentation. Not interpreted in any way by Drake; it is retained by the cache entry and used to generate the description for the corresponding CacheEntryValue in the Context. [in] value_producer Provides the computation that maps from a given Context to the current value that this cache entry should have, as well as a way to allocate storage prior to the computation. [in] prerequisites_of_calc Provides the DependencyTicket list containing a ticket for every Context value on which calc_function may depend when it computes its result. Defaults to {all_sources_ticket()} if unspecified. If the cache value is truly independent of the Context (rare!) say so explicitly by providing the list {nothing_ticket()}; an explicitly empty list {} is forbidden.
Returns
a reference to the newly-created CacheEntry.
Exceptions
 std::exception if given an explicitly empty prerequisite list.

## ◆ DeclareCacheEntry() [2/7]

 CacheEntry& DeclareCacheEntry ( std::string description, std::function< std::unique_ptr< AbstractValue >()> alloc_function, std::function< void(const ContextBase &, AbstractValue *)> calc_function, std::set< DependencyTicket > prerequisites_of_calc = { all_sources_ticket()} )

(Deprecated.)

Deprecated:
This will be removed from Drake on or after "2021-10-01" .

## ◆ DeclareCacheEntry() [3/7]

 CacheEntry & DeclareCacheEntry ( std::string description, ValueType(MySystem::*)() const make, void(MySystem::*)(const MyContext &, ValueType *) const calc, std::set< DependencyTicket > prerequisites_of_calc = { all_sources_ticket()} )

(Deprecated.)

Deprecated:
"This overload for DeclareCacheEntry is rarely the best choice; it is" " unusual for allocation to actually require a boutique callback rather" " than just a Clone of a model_value. We found that most uses of this" " overload hindered readability, because other overloads would often do" " the job more directly. If no existing overload works, you may wrap a" " ValueProducer around your existing make method and call the primary" " DeclareCacheEntry overload that takes a ValueProducer, instead."
This will be removed from Drake on or after "2021-11-01" .

## ◆ DeclareCacheEntry() [4/7]

 CacheEntry & DeclareCacheEntry ( std::string description, const ValueType & model_value, void(MySystem::*)(const MyContext &, ValueType *) const calc, std::set< DependencyTicket > prerequisites_of_calc = { all_sources_ticket()} )

Declares a cache entry by specifying a model value of concrete type ValueType and a calculator function that is a class member function (method) with signature:

void MySystem::CalcCacheValue(const MyContext&, ValueType*) const;

where MySystem is a class derived from SystemBase, MyContext is a class derived from ContextBase, and ValueType is any concrete type such that Value<ValueType> is permitted. (The method names are arbitrary.) Template arguments will be deduced and do not need to be specified. See the primary DeclareCacheEntry() signature above for more information about the parameters and behavior.

drake::Value
Warning
This method is currently specified as public access, but will be demoted to protected access on or after 2021-10-01.

## ◆ DeclareCacheEntry() [5/7]

 CacheEntry & DeclareCacheEntry ( std::string description, const ValueType & model_value, ValueType(MySystem::*)(const MyContext &) const calc, std::set< DependencyTicket > prerequisites_of_calc = { all_sources_ticket()} )

(Deprecated.)

Deprecated:
"This overload for DeclareCacheEntry is dispreferred because it might" " not reuse heap storage from one calculation to the next, and so is" " typically less efficient than the other overloads. A better option" " is to change the ValueType returned by-value to be an output pointer" " instead, and return void. If that is not possible, you may wrap a" " ValueProducer around your existing method and call the primary" " DeclareCacheEntry overload that takes a ValueProducer, instead."
This will be removed from Drake on or after "2021-11-01" .

## ◆ DeclareCacheEntry() [6/7]

 CacheEntry & DeclareCacheEntry ( std::string description, void(MySystem::*)(const MyContext &, ValueType *) const calc, std::set< DependencyTicket > prerequisites_of_calc = { all_sources_ticket()} )

Declares a cache entry by specifying only a calculator function that is a class member function (method) with signature:

void MySystem::CalcCacheValue(const MyContext&, ValueType*) const;

where MySystem is a class derived from SystemBase and MyContext is a class derived from ContextBase. ValueType is a concrete type such that (a) Value<ValueType> is permitted, and (b) ValueType is default constructible. That allows us to create a model value using Value<ValueType>{} (value initialized so numerical types will be zeroed in the model). (The method name is arbitrary.) Template arguments will be deduced and do not need to be specified. See the first DeclareCacheEntry() signature above for more information about the parameters and behavior.

Note
The default constructor will be called once immediately to create a model value, and subsequent allocations will just copy the model value without invoking the constructor again. If you want the constructor invoked again at each allocation (not common), use one of the other signatures to explicitly provide a method for the allocator to call; that method can then invoke the ValueType default constructor each time it is called.
drake::Value
Warning
This method is currently specified as public access, but will be demoted to protected access on or after 2021-10-01.

## ◆ DeclareCacheEntry() [7/7]

 CacheEntry & DeclareCacheEntry ( std::string description, ValueType(MySystem::*)(const MyContext &) const calc, std::set< DependencyTicket > prerequisites_of_calc = { all_sources_ticket()} )

(Deprecated.)

Deprecated:
"This overload for DeclareCacheEntry is dispreferred because it might" " not reuse heap storage from one calculation to the next, and so is" " typically less efficient than the other overloads. A better option" " is to change the ValueType returned by-value to be an output pointer" " instead, and return void. If that is not possible, you may wrap a" " ValueProducer around your existing method and call the primary" " DeclareCacheEntry overload that takes a ValueProducer, instead."
This will be removed from Drake on or after "2021-11-01" .

## ◆ DeclareCacheEntryWithKnownTicket()

 CacheEntry& DeclareCacheEntryWithKnownTicket ( DependencyTicket known_ticket, std::string description, ValueProducer value_producer, std::set< DependencyTicket > prerequisites_of_calc = { all_sources_ticket()} )
protected

(Internal use only) This is for cache entries associated with pre-defined tickets, for example the cache entry for time derivatives.

See the public API for the most-general DeclareCacheEntry() signature for the meanings of the other parameters here.

## ◆ discrete_state_ticket()

 DependencyTicket discrete_state_ticket ( DiscreteStateIndex index ) const

Returns a ticket indicating dependence on a particular discrete state variable xdᵢ (may be a vector).

(We sometimes refer to this as a "discrete variable group".)

xd_ticket() to obtain a ticket for all discrete variables.

## ◆ DoAllocateContext()

 virtual std::unique_ptr DoAllocateContext ( ) const
protectedpure virtual

Derived class implementations should allocate a suitable concrete Context type, then invoke the above InitializeContextBase() method.

A Diagram must then invoke AllocateContext() to obtain each of the subcontexts for its DiagramContext, and must set up inter-subcontext dependencies among its children and between itself and its children. Then context resources such as parameters and state should be allocated.

Implemented in LeafSystem< T >, and LeafSystem< double >.

## ◆ EvalAbstractInput()

 const AbstractValue* EvalAbstractInput ( const ContextBase & context, int port_index ) const

Returns the value of the input port with the given port_index as an AbstractValue, which is permitted for ports of any type.

Causes the value to become up to date first if necessary, delegating to our parent Diagram. Returns a pointer to the port's value, or nullptr if the port is not connected. If you know the actual type, use one of the more-specific signatures.

Precondition
port_index selects an existing input port of this System.
EvalInputValue(), System::EvalVectorInput(), System::EvalEigenVectorInput()

## ◆ EvalAbstractInputImpl()

 const AbstractValue* EvalAbstractInputImpl ( const char * func, const ContextBase & context, InputPortIndex port_index ) const
protected

(Internal use only) Shared code for updating an input port and returning a pointer to its abstract value, or nullptr if the port is not connected.

func should be the user-visible API function name obtained with func.

## ◆ EvalInputValue()

 const V* EvalInputValue ( const ContextBase & context, int port_index ) const

Returns the value of an abstract-valued input port with the given port_index as a value of known type V.

Causes the value to become up to date first if necessary. See EvalAbstractInput() for more information.

The result is returned as a pointer to the input port's value of type V, or nullptr if the port is not connected.

Precondition
port_index selects an existing input port of this System.
the port's value must be retrievable from the stored abstract value using AbstractValue::get_value<V>.
Template Parameters
 V The type of data expected.

## ◆ get_cache_entry()

 const CacheEntry& get_cache_entry ( CacheIndex index ) const

Returns a reference to a CacheEntry given its index.

## ◆ get_context_sizes() [1/2]

 const ContextSizes& get_context_sizes ( ) const
protected

Obtains access to the declared Context partition sizes as accumulated during LeafSystem or Diagram construction .

## ◆ get_context_sizes() [2/2]

 static const ContextSizes& get_context_sizes ( const SystemBase & system )
staticprotected

Allows Diagram to access protected get_context_sizes() recursively on its subsystems.

## ◆ get_input_port_base()

 const InputPortBase& get_input_port_base ( InputPortIndex port_index ) const

Returns a reference to an InputPort given its port_index.

Precondition
port_index selects an existing input port of this System.

## ◆ get_mutable_cache_entry()

 CacheEntry& get_mutable_cache_entry ( CacheIndex index )

(Advanced) Returns a mutable reference to a CacheEntry given its index.

Note that you do not need mutable access to a CacheEntry to modify its value in a Context, so most users should not use this method.

## ◆ get_mutable_context_sizes()

 ContextSizes& get_mutable_context_sizes ( )
protected

Should be used only during LeafSystem or Diagram construction.

## ◆ get_name()

 const std::string& get_name ( ) const

Returns the name last supplied to set_name(), if any.

Diagrams built with DiagramBuilder will always have a default name for every contained subsystem for which no user-provided name is available. Systems created by copying with a scalar type change have the same name as the source system. An empty string is returned if no name has been set.

## ◆ get_output_port_base()

 const OutputPortBase& get_output_port_base ( OutputPortIndex port_index ) const

Returns a reference to an OutputPort given its port_index.

Precondition
port_index selects an existing output port of this System.

## ◆ get_parent_service()

 const internal::SystemParentServiceInterface* get_parent_service ( ) const
protected

Returns a pointer to the service interface of the immediately enclosing Diagram if one has been set, otherwise nullptr.

## ◆ get_system_id()

 internal::SystemId get_system_id ( ) const
protected

(Internal) Gets the id used to tag context data as being created by this system.

## ◆ GetDirectFeedthroughs()

 virtual std::multimap GetDirectFeedthroughs ( ) const
pure virtual

Reports all direct feedthroughs from input ports to output ports.

For a system with m input ports: I = i₀, i₁, ..., iₘ₋₁, and n output ports, O = o₀, o₁, ..., oₙ₋₁, the return map will contain pairs (u, v) such that

• 0 ≤ u < m,
• 0 ≤ v < n,
• and there might be a direct feedthrough from input iᵤ to each output oᵥ.

See DeclareLeafOutputPort documentation for how leaf systems can report their feedthrough.

Implemented in Diagram< T >, Diagram< double >, LeafSystem< T >, and LeafSystem< double >.

## ◆ GetInputPortBaseOrThrow()

 const InputPortBase& GetInputPortBaseOrThrow ( const char * func, int port_index ) const
protected

(Internal use only) Returns the InputPortBase at index port_index, throwing std::exception we don't like the port index.

The name of the public API method that received the bad index is provided in func and is included in the error message.

## ◆ GetOutputPortBaseOrThrow()

 const OutputPortBase& GetOutputPortBaseOrThrow ( const char * func, int port_index ) const
protected

(Internal use only) Returns the OutputPortBase at index port_index, throwing std::exception if we don't like the port index.

The name of the public API method that received the bad index is provided in func and is included in the error message.

## ◆ GetSystemName()

 const std::string& GetSystemName ( ) const
final

Returns a human-readable name for this system, for use in messages and logging.

This will be the same as returned by get_name(), unless that would be an empty string. In that case we return a non-unique placeholder name, currently just "_" (a lone underscore).

## ◆ GetSystemPathname()

 std::string GetSystemPathname ( ) const
final

Generates and returns a human-readable full path name of this subsystem, for use in messages and logging.

The name starts from the root System, with "::" delimiters between parent and child subsystems, with the individual subsystems represented by their names as returned by GetSystemName().

## ◆ GetSystemType()

 std::string GetSystemType ( ) const
final

Returns the most-derived type of this concrete System object as a human-readable string suitable for use in error messages.

The format is as generated by NiceTypeName and will include namespace qualification if present.

NiceTypeName for more specifics.

## ◆ implicit_time_derivatives_residual_size()

 int implicit_time_derivatives_residual_size ( ) const

Returns the size of the implicit time derivatives residual vector.

By default this is the same as num_continuous_states() but a LeafSystem can change it during construction via LeafSystem::DeclareImplicitTimeDerivativesResidualSize().

## ◆ InitializeContextBase()

 void InitializeContextBase ( ContextBase * context ) const
protected

This method must be invoked from within derived class DoAllocateContext() implementations right after the concrete Context object has been allocated.

It allocates cache entries, sets up all intra-Context dependencies, and marks the ContextBase as initialized so that we can verify proper derived-class behavior.

Precondition
The supplied context must not be null and must not already have been initialized.

## ◆ input_port_ticket()

 DependencyTicket input_port_ticket ( InputPortIndex index ) const

Returns a ticket indicating dependence on input port uᵢ indicated by index.

Precondition
index selects an existing input port of this System.

## ◆ ke_ticket()

 static DependencyTicket ke_ticket ( )
static

Returns a ticket for the cache entry that holds the kinetic energy calculation.

System::EvalKineticEnergy()

## ◆ kinematics_ticket()

 static DependencyTicket kinematics_ticket ( )
static

Returns a ticket indicating dependence on all source values that may affect configuration- or velocity-dependent computations.

This ticket depends on the configuration_ticket defined above, and adds in velocity-affecting source values. This does not include time or input ports.

configuration_ticket()
Note
Currently there is no way to declare specific variables and parameters to be configuration- or velocity-affecting so we include all state variables and parameters except for state variables z.

## ◆ MakeFixInputPortTypeChecker()

 virtual std::function MakeFixInputPortTypeChecker ( InputPortIndex port_index ) const
protectedpure virtual

(Internal use only) Given a port_index, returns a function to be called when validating Context::FixInputPort requests.

The function should attempt to throw an exception if the input AbstractValue is invalid, so that errors can be reported at Fix-time instead of EvalInput-time.

## ◆ NextInputPortName()

 std::string NextInputPortName ( std::variant< std::string, UseDefaultName > given_name ) const
protected

(Internal use only) Returns a name for the next input port, using the given name if it isn't kUseDefaultName, otherwise making up a name like "u3" from the next available input port index.

Precondition
given_name must not be empty.

## ◆ NextOutputPortName()

 std::string NextOutputPortName ( std::variant< std::string, UseDefaultName > given_name ) const
protected

(Internal use only) Returns a name for the next output port, using the given name if it isn't kUseDefaultName, otherwise making up a name like "y3" from the next available output port index.

Precondition
given_name must not be empty.

## ◆ nothing_ticket()

 static DependencyTicket nothing_ticket ( )
static

Returns a ticket indicating that a computation does not depend on any source value; that is, it is a constant.

If this appears in a prerequisite list, it must be the only entry.

## ◆ num_abstract_parameters()

 int num_abstract_parameters ( ) const

Returns the number of declared abstract parameters.

## ◆ num_abstract_states()

 int num_abstract_states ( ) const

Returns the number of declared abstract state variables.

## ◆ num_cache_entries()

 int num_cache_entries ( ) const

Returns the number nc of cache entries currently allocated in this System.

These are indexed from 0 to nc-1.

## ◆ num_continuous_states()

 int num_continuous_states ( ) const

Returns the number of declared continuous state variables.

## ◆ num_discrete_state_groups()

 int num_discrete_state_groups ( ) const

Returns the number of declared discrete state groups (each group is a vector-valued discrete state variable).

## ◆ num_input_ports()

 int num_input_ports ( ) const

Returns the number of input ports currently allocated in this System.

These are indexed from 0 to num_input_ports()-1.

## ◆ num_numeric_parameter_groups()

 int num_numeric_parameter_groups ( ) const

Returns the number of declared numeric parameters (each of these is a vector-valued parameter).

## ◆ num_output_ports()

 int num_output_ports ( ) const

Returns the number of output ports currently allocated in this System.

These are indexed from 0 to num_output_ports()-1.

## ◆ num_total_inputs()

 int num_total_inputs ( ) const

Returns the total dimension of all of the vector-valued input ports (as if they were muxed).

## ◆ num_total_outputs()

 int num_total_outputs ( ) const

Returns the total dimension of all of the vector-valued output ports (as if they were muxed).

## ◆ numeric_parameter_ticket()

 DependencyTicket numeric_parameter_ticket ( NumericParameterIndex index ) const

Returns a ticket indicating dependence on a particular numeric parameter pnᵢ (may be a vector).

pn_ticket() to obtain a ticket for all numeric parameters.

## ◆ operator=() [1/2]

 SystemBase& operator= ( SystemBase && )
delete

## ◆ operator=() [2/2]

 SystemBase& operator= ( const SystemBase & )
delete

## ◆ output_port_ticket()

 DependencyTicket output_port_ticket ( OutputPortIndex index ) const

(Internal use only) Returns a ticket indicating dependence on the output port indicated by index.

No user-definable quantities in a system can meaningfully depend on that system's own output ports.

Precondition
index selects an existing output port of this System.

## ◆ pa_ticket()

 static DependencyTicket pa_ticket ( )
static

Returns a ticket indicating dependence on all of the abstract parameters pa in the current Context.

abstract_parameter_ticket() to obtain a ticket for just one abstract parameter.

## ◆ pc_ticket()

 static DependencyTicket pc_ticket ( )
static

Returns a ticket for the cache entry that holds the conservative power calculation.

System::EvalConservativePower()

## ◆ pe_ticket()

 static DependencyTicket pe_ticket ( )
static

Returns a ticket for the cache entry that holds the potential energy calculation.

System::EvalPotentialEnergy()

## ◆ pn_ticket()

 static DependencyTicket pn_ticket ( )
static

Returns a ticket indicating dependence on all of the numerical parameters in the current Context.

numeric_parameter_ticket() to obtain a ticket for just one numeric parameter.

## ◆ pnc_ticket()

 static DependencyTicket pnc_ticket ( )
static

Returns a ticket for the cache entry that holds the non-conservative power calculation.

System::EvalNonConservativePower()

## ◆ q_ticket()

 static DependencyTicket q_ticket ( )
static

Returns a ticket indicating that a computation depends on configuration state variables q.

There is no ticket representing just one of the state variables qᵢ.

## ◆ set_implicit_time_derivatives_residual_size()

 void set_implicit_time_derivatives_residual_size ( int n )
protected

Allows a LeafSystem to override the default size for the implicit time derivatives residual and a Diagram to sum up the total size.

If no value is set, the default size is n=num_continuous_states().

Parameters
 [in] n The size of the residual vector output argument of System::CalcImplicitTimeDerivativesResidual(). If n <= 0 restore to the default, num_continuous_states().
implicit_time_derivatives_residual_size()
LeafSystem::DeclareImplicitTimeDerivativesResidualSize()
System::CalcImplicitTimeDerivativesResidual()

## ◆ set_name()

 void set_name ( const std::string & name )

Sets the name of the system.

Do not use the path delimiter character ':' in the name. When creating a Diagram, names of sibling subsystems should be unique. DiagramBuilder uses this method to assign a unique default name if none is provided.

## ◆ set_parent_service()

 static void set_parent_service ( SystemBase * child, const internal::SystemParentServiceInterface * parent_service )
staticprotected

(Internal use only) Declares that parent_service is the service interface of the Diagram that owns this subsystem.

Aborts if the parent service has already been set to something else.

## ◆ ThrowCantEvaluateInputPort()

 void ThrowCantEvaluateInputPort ( const char * func, InputPortIndex port_index ) const
protected

Throws std::exception because someone called API method func, that requires this input port to be evaluatable, but the port was neither fixed nor connected.

## ◆ ThrowInputPortHasWrongType() [1/2]

 void ThrowInputPortHasWrongType ( const char * func, InputPortIndex port_index, const std::string & expected_type, const std::string & actual_type ) const
protected

Throws std::exception because someone called API method func claiming the input port had some value type that was wrong.

## ◆ ThrowInputPortHasWrongType() [2/2]

 static void ThrowInputPortHasWrongType ( const char * func, const std::string & system_pathname, InputPortIndex , const std::string & port_name, const std::string & expected_type, const std::string & actual_type )
staticprotected

Throws std::exception because someone called API method func claiming the input port had some value type that was wrong.

## ◆ ThrowInputPortIndexOutOfRange()

 void ThrowInputPortIndexOutOfRange ( const char * func, InputPortIndex port_index ) const
protected

Throws std::exception to report bad input port_index that was passed to API method func.

## ◆ ThrowNegativePortIndex()

 void ThrowNegativePortIndex ( const char * func, int port_index ) const
protected

Throws std::exception to report a negative port_index that was passed to API method func.

Caller must ensure that the function name makes it clear what kind of port we're complaining about.

## ◆ ThrowNotAVectorInputPort()

 void ThrowNotAVectorInputPort ( const char * func, InputPortIndex port_index ) const
protected

Throws std::exception because someone misused API method func, that is only allowed for declared-vector input ports, on an abstract port whose index is given here.

## ◆ ThrowOutputPortIndexOutOfRange()

 void ThrowOutputPortIndexOutOfRange ( const char * func, OutputPortIndex port_index ) const
protected

Throws std::exception to report bad output port_index that was passed to API method func.

## ◆ ThrowUnsupportedScalarConversion()

 static void ThrowUnsupportedScalarConversion ( const SystemBase & from, const std::string & destination_type_name )
staticprotected

(Internal use only) Throws a std::exception for unsupported scalar type conversions.

## ◆ ThrowValidateContextMismatch()

 void ThrowValidateContextMismatch ( const ContextBase & ) const
protected

(Internal use only) Throws std::exception with a message that the sanity check(s) given by ValidateContext have failed.

## ◆ time_ticket()

 static DependencyTicket time_ticket ( )
static

Returns a ticket indicating dependence on time.

This is the same ticket for all systems and refers to the same time value.

## ◆ v_ticket()

 static DependencyTicket v_ticket ( )
static

Returns a ticket indicating dependence on velocity state variables v.

This does not also indicate a dependence on configuration variables q – you must list that explicitly or use kinematics_ticket() instead. There is no ticket representing just one of the state variables vᵢ.

## ◆ ValidateContext() [1/2]

 void ValidateContext ( const ContextBase & context ) const
final

Checks whether the given context was created for this system.

Note
This method is sufficiently fast for performance sensitive code.
Exceptions
 std::exception if the System Ids don't match.

## ◆ ValidateContext() [2/2]

 void ValidateContext ( const ContextBase * context ) const

Checks whether the given context was created for this system.

Note
This method is sufficiently fast for performance sensitive code.
Exceptions
 std::exception if the System Ids don't match. std::exception if context is null.

## ◆ ValidateCreatedForThisSystem()

 void ValidateCreatedForThisSystem ( const Clazz & object ) const

Checks whether the given object was created for this system.

Note
This method is sufficiently fast for performance sensitive code.
Exceptions
 std::exception if the System Ids don't match or if object doesn't have an associated System Id. std::exception if the argument type is a pointer and it is null.

## ◆ xa_ticket()

 static DependencyTicket xa_ticket ( )
static

Returns a ticket indicating dependence on all of the abstract state variables in the current Context.

abstract_state_ticket() to obtain a ticket for just one abstract state variable.

## ◆ xc_ticket()

 static DependencyTicket xc_ticket ( )
static

Returns a ticket indicating dependence on all of the continuous state variables q, v, or z.

## ◆ xcdot_ticket()

 static DependencyTicket xcdot_ticket ( )
static

Returns a ticket for the cache entry that holds time derivatives of the continuous variables.

EvalTimeDerivatives()

## ◆ xd_ticket()

 static DependencyTicket xd_ticket ( )
static

Returns a ticket indicating dependence on all of the numerical discrete state variables, in any discrete variable group.