Add irreducible property for variables

Author: YingboMa

src/ModelingToolkit.jl

@@ -176,7 +176,7 @@ export ControlSystem
 export alias_elimination, flatten
 export connect, @connector, Connection, Flow, Stream, instream
 export isinput, isoutput, getbounds, hasbounds, isdisturbance, istunable, getdist, hasdist,
-       tunable_parameters
+       tunable_parameters, isirreducible
 export ode_order_lowering, dae_order_lowering, liouville_transform
 export runge_kutta_discretize
 export PDESystem

src/structural_transformation/StructuralTransformations.jl

@@ -13,7 +13,7 @@ using ModelingToolkit
 using ModelingToolkit: ODESystem, AbstractSystem, var_from_nested_derivative, Differential,
                        states, equations, vars, Symbolic, diff2term, value,
                        operation, arguments, Sym, Term, simplify, solve_for,
-                       isdiffeq, isdifferential, isinput,
+                       isdiffeq, isdifferential, isirreducible,
                        empty_substitutions, get_substitutions,
                        get_tearing_state, get_iv, independent_variables,
                        has_tearing_state, defaults, InvalidSystemException,

src/structural_transformation/utils.jl

@@ -170,7 +170,7 @@ function find_eq_solvables!(state::TearingState, ieq; may_be_zero = false,
     to_rm = Int[]
     for j in 𝑠neighbors(graph, ieq)
         var = fullvars[j]
-        #isinput(var) && continue
+        isirreducible(var) && continue
         a, b, islinear = linear_expansion(term, var)
         a = unwrap(a)
         islinear || continue

src/systems/systemstructure.jl

@@ -8,8 +8,8 @@ using ..ModelingToolkit
 import ..ModelingToolkit: isdiffeq, var_from_nested_derivative, vars!, flatten,
                           value, InvalidSystemException, isdifferential, _iszero,
                           isparameter,
-                          independent_variables, isinput, SparseMatrixCLIL, AbstractSystem,
-                          equations
+                          independent_variables, SparseMatrixCLIL, AbstractSystem,
+                          equations, isirreducible
 using ..BipartiteGraphs
 import ..BipartiteGraphs: invview, complete
 using Graphs
@@ -358,7 +358,7 @@ function linear_subsys_adjmat(state::TransformationState)
             var = fullvars[j]
             a, b, islinear = linear_expansion(term, var)
             a = unwrap(a)
-            if islinear && !(a isa Symbolic) && a isa Number && !isinput(var)
+            if islinear && !(a isa Symbolic) && a isa Number && !isirreducible(var)
                 if a == 1 || a == -1
                     a = convert(Integer, a)
                     linear_term += a * var

src/variables.jl

@@ -4,12 +4,14 @@ struct VariableNoiseType end
 struct VariableDescriptionType end
 struct VariableInput end
 struct VariableOutput end
+struct VariableIrreducible end
 Symbolics.option_to_metadata_type(::Val{:unit}) = VariableUnit
 Symbolics.option_to_metadata_type(::Val{:connect}) = VariableConnectType
 Symbolics.option_to_metadata_type(::Val{:noise}) = VariableNoiseType
 Symbolics.option_to_metadata_type(::Val{:description}) = VariableDescriptionType
 Symbolics.option_to_metadata_type(::Val{:input}) = VariableInput
 Symbolics.option_to_metadata_type(::Val{:output}) = VariableOutput
+Symbolics.option_to_metadata_type(::Val{:irreducible}) = VariableIrreducible
 
 abstract type AbstractConnectType end
 struct Equality <: AbstractConnectType end # Equality connection
@@ -25,6 +27,7 @@ end
 
 isinput(x) = isvarkind(VariableInput, x)
 isoutput(x) = isvarkind(VariableOutput, x)
+isirreducible(x) = isvarkind(VariableIrreducible, x) || isinput(x)
 
 """
 $(SIGNATURES)