The System type

struct System <: ModelingToolkit.IntermediateDeprecationSystem

A symbolic representation of a numerical system to be solved. This is a recursive tree-like data structure - each system can contain additional subsystems. As such, it implements the AbstractTrees.jl interface to enable exploring the hierarchical structure.

Fields

• tag::UInt64: This field is internal API. It may be removed or changed without notice in a non-breaking release. Usage of this field is not advised.

  A unique integer tag for the system.

• eqs::Vector{Equation}: The equations of the system.

• noise_eqs::Union{Nothing, AbstractMatrix, AbstractVector}: The noise terms for each equation of the system. This field is only used for flattened systems. To represent noise in a hierarchical system, use brownians. In a system with N equations and K independent brownian variables, this should be an N x K matrix. In the special case where N == K and each equation has independent noise, this noise matrix is diagonal. Diagonal noise can be specified by providing an N length vector. If this field is nothing, the system does not have noise.

• jumps::Vector{Union{JumpProcesses.ConstantRateJump, JumpProcesses.MassActionJump, JumpProcesses.VariableRateJump}}: Jumps associated with the system. Each jump can be a VariableRateJump, ConstantRateJump or MassActionJump. See JumpProcesses.jl for more information.

• constraints::Vector{Union{Equation, Inequality}}: The constraints of the system. This can be used to represent the constraints in an optimal-control problem or boundary-value differential equation, or the constraints in a constrained optimization.

• costs::Vector{<:Union{Real, SymbolicUtils.BasicSymbolic}}: The costs of the system. This can be the cost in an optimal-control problem, or the loss of an optimization problem. Scalar loss values must also be provided as a single- element vector.

• consolidate::Any: A function which combines costs into a scalar value. This should take two arguments, the costs of this system and the consolidated costs of all subsystems in the order they are present in the systems field. It should return a scalar cost that combines all of the individual values. This defaults to a function that simply sums all cost values.

• unknowns::Vector: The variables being solved for by this system. For example, in a differential equation system, this contains the dependent variables.

• ps::Vector: The parameters of the system. Parameters can either be variables that parameterize the problem being solved for (e.g. the spring constant of a mass-spring system) or additional unknowns not part of the main dynamics of the system (e.g. discrete/clocked variables in a hybrid ODE).

• brownians::Vector: The brownian variables of the system, created via @brownians. Each brownian variable represents an independent noise. A system with brownians cannot be simulated directly. It needs to be compiled using mtkcompile into noise_eqs.

• iv::Union{Nothing, SymbolicUtils.BasicSymbolic{Real}}: The independent variable for a time-dependent system, or nothing for a time-independent system.

• observed::Vector{Equation}: Equations that compute variables of a system that have been eliminated from the set of unknowns by mtkcompile. More generally, this contains all variables that can be computed from the unknowns and parameters and do not need to be solved for. Such variables are termed as "observables". Each equation must be of the form observable ~ expression and observables cannot appear on the LHS of multiple equations. Equations must be sorted such that every observable appears on the left hand side of an equation before it appears on the right hand side of any other equation.

• parameter_dependencies::Vector{Equation}: This field is internal API. It may be removed or changed without notice in a non-breaking release. Usage of this field is not advised.

  All the explicit equations relating parameters. Equations here only contain parameters and are in the same format as observed.

• var_to_name::Dict{Symbol, Any}: This field is internal API. It may be removed or changed without notice in a non-breaking release. Usage of this field is not advised.

  A mapping from the name of a variable to the actual symbolic variable in the system. This is used to enable getproperty syntax to access variables of a system.

• name::Symbol: The name of the system.

• description::String: An optional description for the system.

• defaults::Dict: Default values that variables (unknowns/observables/parameters) should take when constructing a numerical problem from the system. These values can be overridden by initial values provided to the problem constructor. Defaults of parent systems take priority over those in child systems.

• guesses::Dict: Guess values for variables of a system that are solved for during initialization.

• systems::Vector{System}: A list of subsystems of this system. Used for hierarchically building models.

• initialization_eqs::Vector{Equation}: Equations that must be satisfied during initialization of the numerical problem created from this system. For time-dependent systems, these equations are not valid after the initial time.

• continuous_events::Vector{ModelingToolkit.SymbolicContinuousCallback}: Symbolic representation of continuous events in a dynamical system. See SymbolicContinuousCallback.

• discrete_events::Vector{ModelingToolkit.SymbolicDiscreteCallback}: Symbolic representation of discrete events in a dynamica system. See SymbolicDiscreteCallback.

• connector_type::Any: This field is internal API. It may be removed or changed without notice in a non-breaking release. Usage of this field is not advised.

  If this system is a connector, the type of connector it is.

• assertions::Dict{SymbolicUtils.BasicSymbolic, String}: A map from expressions that must be through throughout the solution process to an associated error message. By default these assertions cause the generated code to output NaNs if violated, but can be made to error using debug_system.

• metadata::Base.ImmutableDict{DataType, Any}: The metadata associated with this system, as a Base.ImmutableDict. This follows the same interface as SymbolicUtils.jl. Metadata can be queried and updated using SymbolicUtils.getmetadata and SymbolicUtils.setmetadata respectively.

• gui_metadata::Any: This field is internal API. It may be removed or changed without notice in a non-breaking release. Usage of this field is not advised.

  Metadata added by the @mtkmodel macro.

• is_dde::Bool: Whether the system contains delay terms. This is inferred from the equations, but can also be provided explicitly.

• tstops::Vector{Any}: Extra time points for the integrator to stop at. These can be numeric values, or expressions of parameters and time.

• tearing_state::Any: The TearingState of the system post-simplification with mtkcompile.

• namespacing::Bool: Whether the system namespaces variables accessed via getproperty. completed systems do not namespace, but this flag can be toggled independently of complete using toggle_namespacing.

• complete::Bool: Whether the system is marked as "complete". Completed systems cannot be used as subsystems.

• index_cache::Union{Nothing, ModelingToolkit.IndexCache}: This field is internal API. It may be removed or changed without notice in a non-breaking release. Usage of this field is not advised.

  For systems simplified or completed with split = true (the default) this contains an IndexCache which aids in symbolic indexing. If this field is nothing, the system is either not completed, or completed with split = false.

• ignored_connections::Union{Nothing, Vector{Connection}}: This field is internal API. It may be removed or changed without notice in a non-breaking release. Usage of this field is not advised.

  Connections that should be ignored because they were removed by an analysis point transformation. The first element of the tuple contains all such "standard" connections (ones between connector systems) and the second contains all such causal variable connections.

• preface::Any: SymbolicUtils.Code.Assignments to prepend to all code generated from this system.

• parent::Union{Nothing, System}: After simplification with mtkcompile, this field contains the unsimplified system with the hierarchical structure. There may be multiple levels of parents. The root parent is used for accessing variables via getproperty syntax.

• initializesystem::Union{Nothing, System}: A custom initialization system to use if no initial conditions are provided for the unknowns or observables of this system.

• is_initializesystem::Bool: Whether the current system is an initialization system.

• is_discrete::Bool

• isscheduled::Bool: This field is internal API. It may be removed or changed without notice in a non-breaking release. Usage of this field is not advised.

  Whether the system has been simplified by mtkcompile.

• schedule::Union{Nothing, ModelingToolkit.Schedule}: This field is internal API. It may be removed or changed without notice in a non-breaking release. Usage of this field is not advised.

  The Schedule containing additional information about the simplified system.

NonlinearSystem(sys::System) -> Any

Given a time-dependent system sys of ODEs, convert it to a time-independent system of nonlinear equations that solve for the steady-state of the unknowns. This is done by replacing every derivative D(x) of an unknown x with zero. Note that this process does not retain noise equations, brownian terms, jumps or costs associated with sys. All other information such as defaults, guesses, observed and initialization equations are retained. The independent variable of sys becomes a parameter of the returned system.

If sys is hierarchical (it contains subsystems) this transformation will be applied recursively to all subsystems. The output system will be marked as complete if and only if the input system is also complete. This also retains the split flag passed to complete.

See also: complete.

SDESystem(eqs::Vector{Equation}, noise, iv; is_scalar_noise = false, kwargs...)

Construct a system of equations with associated noise terms. Instead of specifying noise using @brownians variables, it is specified using a noise matrix noise. iv is the independent variable of the system.

In the general case, noise should be a N x M matrix where N is the number of equations (length(eqs)) and M is the number of independent random variables. noise[i, j] is the diffusion term for equation i and random variable j. If the noise is diagonal (N == M and noise[i, j] == 0 for all i != j) it can be specified as a Vector of length N corresponding to the diagonal of the noise matrix. As a special case, if all equations have the same noise then all rows of noise are identical. This is known as "scalar noise". In this case, noise can be a Vector corresponding to the repeated row and is_scalar_noise must be true.

Note that systems created in this manner cannot be used hierarchically. This should only be used to construct flattened systems. To use such a system hierarchically, it must be converted to use brownian variables using noise_to_brownians. mtkcompile will automatically perform this conversion.

All keyword arguments are the same as those of the System constructor.

SDESystem(eqs::Vector{Equation}, noise, iv, dvs, ps; is_scalar_noise = false, kwargs...)

Identical to the 3-argument SDESystem constructor, but uses the explicitly provided dvs and ps for unknowns and parameters of the system.

SDESystem(sys::System, noise; kwargs...)

Attach the given noise matrix noise to the system sys.

JumpSystem(jumps, iv; kwargs...)

Construct a System to solve a system of jump equations. jumps is an array of jumps, expressed using JumpProcesses.MassActionJump, JumpProcesses.ConstantRateJump and JumpProcesses.VariableRateJump. It can also include standard equations to simulate jump-diffusion processes. iv should be the independent variable of the system.

All keyword arguments are the same as those of the System constructor.

JumpSystem(jumps, iv, dvs, ps; kwargs...)

Identical to the 2-argument JumpSystem constructor, but uses the explicitly provided dvs and ps for unknowns and parameters of the system.

OptimizationSystem(cost; kwargs...)

Construct a time-independent System for optimizing the specified scalar cost. The system will have no equations.

Unknowns and parameters of the system are inferred from the cost and other values (such as defaults) passed to it.

All keyword arguments are the same as those of the System constructor.

OptimizationSystem(cost, dvs, ps; kwargs...)

Identical to the corresponding single-argument OptimizationSystem constructor, except the unknowns and parameters are specified by passing arrays of symbolic variables to dvs and ps respectively.

OptimizationSystem(cost::Array; kwargs...)

Construct a time-independent System for optimizing the specified multi-objective cost. The cost will be reduced to a scalar using the consolidate function. This defaults to summing the specified cost and that of all subsystems. The system will have no equations.

Unknowns and parameters of the system are inferred from the cost and other values (such as defaults) passed to it.

All keyword arguments are the same as those of the System constructor.

OptimizationSystem(cost::Array, dvs, ps; kwargs...)

Identical to the corresponding single-argument OptimizationSystem constructor, except the unknowns and parameters are specified by passing arrays of symbolic variables to dvs and ps respectively.

has_eqs(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field eqs.

See also get_eqs.

get_eqs(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field eqs of a system sys. It only includes eqs local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_eqs.

equations(sys::ModelingToolkit.AbstractSystem) -> Any

Get the flattened equations of the system sys and its subsystems. It may include some abbreviations and aliases of observables. It is often the most useful way to inspect the equations of a system.

See also full_equations and ModelingToolkit.get_eqs.

equations_toplevel(sys::AbstractSystem)

Replicates the behaviour of equations, but ignores equations of subsystems.

Notes:

• Cannot be applied to non-complete systems.

full_equations(
    sys::ModelingToolkit.AbstractSystem;
    simplify
) -> Any

Like equations(sys), but also substitutes the observed equations eliminated from the equations during mtkcompile. These equations matches generated numerical code.

See also equations and ModelingToolkit.get_eqs.

has_noise_eqs(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field noise_eqs.

See also get_noise_eqs.

get_noise_eqs(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field noise_eqs of a system sys. It only includes noise_eqs local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_noise_eqs.

has_jumps(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field jumps.

See also get_jumps.

get_jumps(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field jumps of a system sys. It only includes jumps local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_jumps.

jumps(sys::ModelingToolkit.AbstractSystem) -> Any

Get the flattened jumps of the system. In other words, obtain all of the jumps in sys and all the subsystems of sys (appropriately namespaced).

has_constraints(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field constraints.

See also get_constraints.

get_constraints(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field constraints of a system sys. It only includes constraints local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_constraints.

constraints(sys::ModelingToolkit.AbstractSystem) -> Any

Get all constraints in the system sys and all of its subsystems, appropriately namespaced.

has_costs(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field costs.

See also get_costs.

get_costs(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field costs of a system sys. It only includes costs local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_costs.

cost(sys::ModelingToolkit.AbstractSystem) -> Any

Recursively consolidate the cost vector of sys and all subsystems of sys, returning the final scalar cost function.

has_consolidate(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field consolidate.

See also get_consolidate.

get_consolidate(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field consolidate of a system sys. It only includes consolidate local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_consolidate.

has_unknowns(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field unknowns.

See also get_unknowns.

get_unknowns(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field unknowns of a system sys. It only includes unknowns local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_unknowns.

unknowns(sys::ModelingToolkit.AbstractSystem) -> Any

Get the unknown variables of the system sys and its subsystems. These must be explicitly solved for, unlike observables(sys).

See also ModelingToolkit.get_unknowns.

unknowns_toplevel(sys::AbstractSystem)

Replicates the behaviour of unknowns, but ignores unknowns of subsystems.

has_ps(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field ps.

See also get_ps.

get_ps(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field ps of a system sys. It only includes ps local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_ps.

parameters(
    sys::ModelingToolkit.AbstractSystem;
    initial_parameters
) -> Any

Get the parameters of the system sys and its subsystems.

See also @parameters and ModelingToolkit.get_ps.

parameters_toplevel(sys::AbstractSystem)

Replicates the behaviour of parameters, but ignores parameters of subsystems.

tunable_parameters(sys, p = parameters(sys; initial_parameters = true); default=true)

Get all parameters of sys that are marked as tunable.

Keyword argument default indicates whether variables without tunable metadata are to be considered tunable or not.

Create a tunable parameter by

@parameters u [tunable=true]

For systems created with split = true (the default) and default = true passed to this function, the order of parameters returned is the order in which they are stored in the tunables portion of MTKParameters. Note that array variables will not be scalarized. To obtain the flattened representation of the tunables portion, call Symbolics.scalarize(tunable_parameters(sys)) and concatenate the resulting arrays.

See also getbounds, istunable, MTKParameters, complete

has_brownians(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field brownians.

See also get_brownians.

get_brownians(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field brownians of a system sys. It only includes brownians local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_brownians.

brownians(sys::ModelingToolkit.AbstractSystem) -> Any

Get all of the brownian variables involved in the system sys and all subsystems, appropriately namespaced.

has_iv(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field iv.

See also get_iv.

get_iv(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field iv of a system sys. It only includes iv local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_iv.

has_observed(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field observed.

See also get_observed.

get_observed(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field observed of a system sys. It only includes observed local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_observed.

observed(sys::ModelingToolkit.AbstractSystem) -> Any

Get the observed equations of the system sys and its subsystems. These can be expressed in terms of unknowns(sys), and do not have to be explicitly solved for.

See also observables and ModelingToolkit.get_observed().

observables(sys::ModelingToolkit.AbstractSystem) -> Any

Get the observed variables of the system sys and its subsystems. These can be expressed in terms of unknowns(sys), and do not have to be explicitly solved for. It is equivalent to all left hand sides of observed(sys).

See also observed.

has_name(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field name.

See also get_name.

get_name(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field name of a system sys. It only includes name local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_name.

nameof(sys::ModelingToolkit.AbstractSystem) -> Any

Obtain the name of sys.

has_description(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field description.

See also get_description.

get_description(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field description of a system sys. It only includes description local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_description.

description(sys::ModelingToolkit.AbstractSystem) -> Any

Obtain the description associated with sys if present, and an empty string otherwise.

has_defaults(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field defaults.

See also get_defaults.

get_defaults(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field defaults of a system sys. It only includes defaults local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_defaults.

defaults(sys::ModelingToolkit.AbstractSystem) -> Any

Get the default values of the system sys and its subsystems. If they are not explicitly provided, variables and parameters are initialized to these values.

See also initialization_equations and ModelingToolkit.get_defaults.

has_guesses(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field guesses.

See also get_guesses.

get_guesses(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field guesses of a system sys. It only includes guesses local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_guesses.

guesses(sys::ModelingToolkit.AbstractSystem) -> Any

Get the guesses for variables in the initialization system of the system sys and its subsystems.

See also initialization_equations and ModelingToolkit.get_guesses.

get_systems(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field systems of a system sys. It only includes systems local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_systems.

has_initialization_eqs(
    sys::ModelingToolkit.AbstractSystem
) -> Bool

Returns whether the system sys has the internal field initialization_eqs.

See also get_initialization_eqs.

get_initialization_eqs(
    sys::ModelingToolkit.AbstractSystem
) -> Any

Get the internal field initialization_eqs of a system sys. It only includes initialization_eqs local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_initialization_eqs.

initialization_equations(
    sys::ModelingToolkit.AbstractSystem
) -> Any

Get the initialization equations of the system sys and its subsystems.

See also guesses, defaults and ModelingToolkit.get_initialization_eqs.

has_continuous_events(
    sys::ModelingToolkit.AbstractSystem
) -> Bool

Returns whether the system sys has the internal field continuous_events.

See also get_continuous_events.

get_continuous_events(
    sys::ModelingToolkit.AbstractSystem
) -> Any

Get the internal field continuous_events of a system sys. It only includes continuous_events local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_continuous_events.

continuous_events(sys::AbstractSystem)::Vector{SymbolicContinuousCallback}

Returns a vector of all the continuous_events in an abstract system and its component subsystems. The SymbolicContinuousCallbacks in the returned vector are structs with two fields: eqs and affect which correspond to the first and second elements of a Pair used to define an event, i.e. eqs => affect.

See also get_continuous_events, which only returns the events of the top-level system.

continuous_events_toplevel(sys::AbstractSystem)

Replicates the behaviour of continuous_events, but ignores events of subsystems.

Notes:

• Cannot be applied to non-complete systems.

has_discrete_events(
    sys::ModelingToolkit.AbstractSystem
) -> Bool

Returns whether the system sys has the internal field discrete_events.

See also get_discrete_events.

get_discrete_events(
    sys::ModelingToolkit.AbstractSystem
) -> Any

Get the internal field discrete_events of a system sys. It only includes discrete_events local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_discrete_events.

discrete_events_toplevel(sys::AbstractSystem)

Replicates the behaviour of discrete_events, but ignores events of subsystems.

Notes:

• Cannot be applied to non-complete systems.

has_assertions(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field assertions.

See also get_assertions.

get_assertions(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field assertions of a system sys. It only includes assertions local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_assertions.

assertions(sys::ModelingToolkit.AbstractSystem) -> Any

Get the assertions for a system sys and its subsystems.

has_metadata(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field metadata.

See also get_metadata.

get_metadata(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field metadata of a system sys. It only includes metadata local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_metadata.

getmetadata(
    sys::ModelingToolkit.AbstractSystem,
    k::DataType,
    default
) -> Any

Get the metadata associated with key k in system sys or default if it does not exist.

setmetadata(
    sys::ModelingToolkit.AbstractSystem,
    k::DataType,
    v
) -> Any

Set the metadata associated with key k in system sys to value v. This is an out-of-place operation, and will return a shallow copy of sys with the appropriate metadata values.

has_is_dde(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field is_dde.

See also get_is_dde.

get_is_dde(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field is_dde of a system sys. It only includes is_dde local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_is_dde.

is_dde(sys::AbstractSystem)

Return a boolean indicating whether a system represents a set of delay differential equations.

has_tstops(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field tstops.

See also get_tstops.

get_tstops(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field tstops of a system sys. It only includes tstops local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_tstops.

symbolic_tstops(sys::ModelingToolkit.AbstractSystem) -> Any

Get the tstops present in sys and its subsystems, appropriately namespaced.

has_tearing_state(
    sys::ModelingToolkit.AbstractSystem
) -> Bool

Returns whether the system sys has the internal field tearing_state.

See also get_tearing_state.

get_tearing_state(
    sys::ModelingToolkit.AbstractSystem
) -> Any

Get the internal field tearing_state of a system sys. It only includes tearing_state local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_tearing_state.

does_namespacing(sys::ModelingToolkit.AbstractSystem) -> Any

Check whether a system performs namespacing.

toggle_namespacing(
    sys::ModelingToolkit.AbstractSystem,
    value::Bool;
    safe
) -> Any

Return a new sys with namespacing enabled or disabled, depending on value. The keyword argument safe denotes whether systems that do not support such a toggle should error or be ignored.

iscomplete(sys::ModelingToolkit.AbstractSystem) -> Any

Check whether a system is marked as complete.

has_preface(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field preface.

See also get_preface.

get_preface(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field preface of a system sys. It only includes preface local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_preface.

preface(sys::ModelingToolkit.AbstractSystem) -> Any

Obtain the preface associated with sys and all of its subsystems, appropriately namespaced.

has_parent(sys::ModelingToolkit.AbstractSystem) -> Bool

Returns whether the system sys has the internal field parent.

See also get_parent.

get_parent(sys::ModelingToolkit.AbstractSystem) -> Any

Get the internal field parent of a system sys. It only includes parent local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_parent.

has_initializesystem(
    sys::ModelingToolkit.AbstractSystem
) -> Bool

Returns whether the system sys has the internal field initializesystem.

See also get_initializesystem.

get_initializesystem(
    sys::ModelingToolkit.AbstractSystem
) -> Any

Get the internal field initializesystem of a system sys. It only includes initializesystem local to sys; not those of its subsystems, like unknowns(sys), parameters(sys) and equations(sys) does.

See also has_initializesystem.

is_initializesystem(
    sys::ModelingToolkit.AbstractSystem
) -> Any

Check if the given system is an initialization system.

Base.getproperty(sys::AbstractSystem, name::Symbol)

Access the subsystem, variable or analysis point of sys named name. To check if sys will namespace the returned value, use ModelingToolkit.does_namespacing(sys).

See also: ModelingToolkit.does_namespacing.

has_diff_eqs(sys::AbstractSystem)

Return true if a system contains at least one differential equation (i.e. an equation with a differential term). Note that this does not consider subsystems, and only takes into account equations in the top-level system.

Example:

using ModelingToolkit
using ModelingToolkit: t_nounits as t, D_nounits as D
@parameters p d
@variables X(t)
eq1 = D(X) ~ p - d*X
eq2 = 0 ~ p - d*X
@named osys1 = tem([eq1], t)
@named osys2 = tem([eq2], t)
osys12 = compose(osys1, [osys2])
osys21 = compose(osys2, [osys1])

has_diff_eqs(osys12) # returns `true`.
has_diff_eqs(osys21) # returns `false`.

has_alg_eqs(sys::AbstractSystem)

For a system, returns true if it contain at least one algebraic equation (i.e. that does not contain any differentials) in its top-level system.

Example:

using ModelingToolkit
using ModelingToolkit: t_nounits as t, D_nounits as D
@parameters p d
@variables X(t)
eq1 = D(X) ~ p - d*X
eq2 = 0 ~ p - d*X
@named osys1 = System([eq1], t)
@named osys2 = System([eq2], t)
osys12 = compose(osys1, [osys2])
osys21 = compose(osys2, [osys1])

has_alg_eqs(osys12) # returns `false`.
has_alg_eqs(osys21) # returns `true`.

get_diff_eqs(sys::AbstractSystem)

For a system, returns a vector of all differential equations (i.e. that does contain a differential) in its top-level system.

Example:

using ModelingToolkit
using ModelingToolkit: t_nounits as t, D_nounits as D
@parameters p d
@variables X(t)
eq1 = D(X) ~ p - d*X
eq2 = 0 ~ p - d*X
@named osys1 = tem([eq1], t)
@named osys2 = tem([eq2], t)
osys12 = compose(osys1, [osys2])
osys21 = compose(osys2, [osys1])

get_diff_eqs(osys12) # returns `[Differential(t)(X(t)) ~ p - d*X(t)]`.
get_diff_eqs(osys21) # returns `Equation[]``.

get_alg_eqs(sys::AbstractSystem)

For a system, returns a vector of all algebraic equations (i.e. that does not contain any differentials) in its top-level system.

Example:

using ModelingToolkit
using ModelingToolkit: t_nounits as t, D_nounits as D
@parameters p d
@variables X(t)
eq1 = D(X) ~ p - d*X
eq2 = 0 ~ p - d*X
@named osys1 = ([eq1], t)
@named osys2 = ([eq2], t)
osys12 = compose(sys1, [osys2])
osys21 = compose(osys2, [osys1])

get_alg_eqs(osys12) # returns `Equation[]`.
get_alg_eqs(osys21) # returns `[0 ~ p - d*X(t)]`.

has_diff_equations(sys::AbstractSystem)

For a system, returns true if it contain at least one differential equation (i.e. that contain a differential).

Example:

using ModelingToolkit
using ModelingToolkit: t_nounits as t, D_nounits as D
@parameters p d
@variables X(t)
eq1 = D(X) ~ p - d*X
eq2 = 0 ~ p - d*X
@named osys1 = System([eq1], t)
@named osys2 = System([eq2], t)

has_diff_equations(osys1) # returns `true`.
has_diff_equations(osys2) # returns `false`.

has_alg_equations(sys::AbstractSystem)

For a system, returns true if it contain at least one algebraic equation (i.e. that does not contain any differentials).

Example:

using ModelingToolkit
using ModelingToolkit: t_nounits as t, D_nounits as D
@parameters p d
@variables X(t)
eq1 = D(X) ~ p - d*X
eq2 = 0 ~ p - d*X
@named osys1 = System([eq1], t)
@named osys2 = System([eq2], t)

has_alg_equations(osys1) # returns `false`.
has_alg_equations(osys2) # returns `true`.

diff_equations(sys::AbstractSystem)

For a system, returns a vector of all its differential equations (i.e. that does contain a differential).

Example: ```julia using ModelingToolkit using ModelingToolkit: tnounits as t, Dnounits as D @parameters p d @variables X(t) eq1 = D(X) ~ p - dX eq2 = 0 ~ p - dX @named osys = System([eq1, eq2], t)

diff_equations(osys) # returns [Differential(t)(X(t)) ~ p - d*X(t)].

alg_equations(sys::AbstractSystem)

For a system, returns a vector of all its algebraic equations (i.e. that does not contain any differentials).

Example: ```julia using ModelingToolkit using ModelingToolkit: tnounits as t, Dnounits as D @parameters p d @variables X(t) eq1 = D(X) ~ p - dX eq2 = 0 ~ p - dX @named osys = System([eq1, eq2], t)

alg_equations(osys) # returns [0 ~ p - d*X(t)].

is_alg_equation(eq)

Return true if the input is an algebraic equation, i.e. an equation that does not contain any differentials.

Example:

using ModelingToolkit
using ModelingToolkit: t_nounits as t, D_nounits as D
@parameters p d
@variables X(t)
eq1 = D(X) ~ p - d*X
eq2 = 0 ~ p - d*X

is_alg_equation(eq1) # false
is_alg_equation(eq2) # true

is_diff_equation(eq)

Return true if the input is a differential equation, i.e. an equation that contains a differential term.

Example:

using ModelingToolkit
using ModelingToolkit: t_nounits as t, D_nounits as D
@parameters p d
@variables X(t)
eq1 = D(X) ~ p - d*X
eq2 = 0 ~ p - d*X

is_diff_equation(eq1) # true
is_diff_equation(eq2) # false

parse_variable(
    sys::ModelingToolkit.AbstractSystem,
    str::AbstractString
) -> Any

Return the variable in sys referred to by its string representation str. Roughly supports the following CFG:

varname                  = "D(" varname ")" | "Differential(" iv ")(" varname ")" | arrvar | maybe_dummy_var
arrvar                   = maybe_dummy_var "[idxs...]"
idxs                     = int | int "," idxs
maybe_dummy_var          = namespacedvar | namespacedvar "(" iv ")" |
                           namespacedvar "(" iv ")" "ˍ" ts | namespacedvar "ˍ" ts |
                           namespacedvar "ˍ" ts "(" iv ")"
ts                       = iv | iv ts
namespacedvar            = ident "₊" namespacedvar | ident "." namespacedvar | ident

Where iv is the independent variable, int is an integer and ident is an identifier.

dump_unknowns(sys::AbstractSystem)

Return an array of NamedTuples containing the metadata associated with each unknown in sys. Also includes the default value of the unknown, if provided.

using ModelingToolkit
using DynamicQuantities
using ModelingToolkit: t, D

@parameters p = 1.0, [description = "My parameter", tunable = false] q = 2.0, [description = "Other parameter"]
@variables x(t) = 3.0 [unit = u"m"]
@named sys = System(Equation[], t, [x], [p, q])
ModelingToolkit.dump_unknowns(sys)

See also: ModelingToolkit.dump_variable_metadata, ModelingToolkit.dump_parameters

dump_parameters(sys::AbstractSystem)

Return an array of NamedTuples containing the metadata associated with each parameter in sys. Also includes the default value of the parameter, if provided.

using ModelingToolkit
using DynamicQuantities
using ModelingToolkit: t, D

@parameters p = 1.0, [description = "My parameter", tunable = false] q = 2.0, [description = "Other parameter"]
@variables x(t) = 3.0 [unit = u"m"]
@named sys = System(Equation[], t, [x], [p, q])
ModelingToolkit.dump_parameters(sys)

See also: ModelingToolkit.dump_variable_metadata, ModelingToolkit.dump_unknowns

dump_variable_metadata(var)

Return all the metadata associated with symbolic variable var as a NamedTuple.

using ModelingToolkit

@parameters p::Int [description = "My description", bounds = (0.5, 1.5)]
ModelingToolkit.dump_variable_metadata(p)

inputs(sys)

Return all variables that mare marked as inputs. See also unbound_inputs See also bound_inputs, unbound_inputs

outputs(sys)

Return all variables that mare marked as outputs. See also unbound_outputs See also bound_outputs, unbound_outputs

bound_inputs(sys)

Return inputs that are bound within the system, i.e., internal inputs See also bound_inputs, unbound_inputs, bound_outputs, unbound_outputs

unbound_inputs(sys)

Return inputs that are not bound within the system, i.e., external inputs See also bound_inputs, unbound_inputs, bound_outputs, unbound_outputs

bound_outputs(sys)

Return outputs that are bound within the system, i.e., internal outputs See also bound_inputs, unbound_inputs, bound_outputs, unbound_outputs

unbound_outputs(sys)

Return outputs that are not bound within the system, i.e., external outputs See also bound_inputs, unbound_inputs, bound_outputs, unbound_outputs

is_bound(sys, u)

Determine whether input/output variable u is "bound" within the system, i.e., if it's to be considered internal to sys. A variable/signal is considered bound if it appears in an equation together with variables from other subsystems. The typical usecase for this function is to determine whether the input to an IO component is connected to another component, or if it remains an external input that the user has to supply before simulating the system.

See also bound_inputs, unbound_inputs, bound_outputs, unbound_outputs

debug_system(sys::AbstractSystem; functions = [log, sqrt, (^), /, inv, asin, acos], error_nonfinite = true)

Wrap functions in sys so any error thrown in them shows helpful symbolic-numeric information about its input. If error_nonfinite, functions that output nonfinite values (like Inf or NaN) also display errors, even though the raw function itself does not throw an exception (like 1/0). For example:

julia> sys = debug_system(complete(sys))

julia> prob = ODEProblem(sys, [0.0, 2.0], (0.0, 1.0))

julia> prob.f(prob.u0, prob.p, 0.0)
ERROR: Function /(1, sin(P(t))) output non-finite value Inf with input
  1 => 1
  sin(P(t)) => 0.0

Additionally, all assertions in the system are optionally logged when they fail. A new parameter is also added to the system which controls whether the message associated with each assertion will be logged when the assertion fails. This parameter defaults to true and can be toggled by symbolic indexing with ModelingToolkit.ASSERTION_LOG_VARIABLE. For example, prob.ps[ModelingToolkit.ASSERTION_LOG_VARIABLE] = false will disable logging.