Remove the reduced_states field

Author: YingboMa

src/structural_transformation/StructuralTransformations.jl

@@ -16,7 +16,7 @@ using ModelingToolkit: ODESystem, var_from_nested_derivative, Differential,
                        states, equations, vars, Symbolic, diff2term, value,
                        operation, arguments, Sym, Term, simplify, solve_for,
                        isdiffeq, isdifferential,
-                       get_structure, get_reduced_states, defaults
+                       get_structure, defaults
 
 using ModelingToolkit.BipartiteGraphs
 using ModelingToolkit.SystemStructures

src/structural_transformation/tearing.jl

@@ -187,8 +187,7 @@ function tearing_reassemble(sys; simplify=false)
     @set! sys.structure = s
     @set! sys.eqs = neweqs
     @set! sys.states = newstates
-    @set! sys.reduced_states = [get_reduced_states(sys); solvars]
-    @set! sys.observed = vcat(observed(sys), obseqs)
+    @set! sys.observed = [observed(sys); obseqs]
     return sys
 end
 

src/systems/abstractsystem.jl

@@ -153,7 +153,6 @@ for prop in [
              :inequality_constraints
              :controls
              :loss
-             :reduced_states
              :bcs
              :domain
              :depvars
@@ -524,7 +523,7 @@ topological sort of the observed equations.
 """
 function structural_simplify(sys::AbstractSystem)
     sys = tearing(alias_elimination(sys))
-    fullstates = [get_reduced_states(sys); states(sys)]
+    fullstates = [map(eq->eq.lhs, observed(sys)); states(sys)]
     @set! sys.observed = topsort_equations(observed(sys), fullstates)
     return sys
 end

src/systems/alias_elimination.jl

@@ -20,11 +20,9 @@ function alias_elimination(sys)
     @unpack fullvars, graph = s
 
     n_reduced_states = length(v_eliminated) - n_null_vars
-    reduced_states = similar(v_eliminated, Any, n_reduced_states)
     subs = OrderedDict()
     if n_reduced_states > 0
         for (i, v) in enumerate(@view v_eliminated[n_null_vars+1:end])
-            reduced_states[i] = fullvars[v]
             subs[fullvars[v]] = iszeroterm(v_types, v) ? 0.0 :
                                 isalias(v_types, v) ? fullvars[alias(v_types, v)] :
                                 -fullvars[negalias(v_types, v)]
@@ -67,8 +65,7 @@ function alias_elimination(sys)
 
     @set! sys.eqs = eqs
     @set! sys.states = newstates
-    @set! sys.reduced_states = [get_reduced_states(sys); reduced_states]
-    @set! sys.observed = [get_observed(sys); [lhs ~ rhs for (lhs, rhs) in pairs(subs)]]
+    @set! sys.observed = [observed(sys); [lhs ~ rhs for (lhs, rhs) in pairs(subs)]]
     @set! sys.structure = nothing
     return sys
 end

src/systems/diffeqs/odesystem.jl

@@ -69,7 +69,6 @@ struct ODESystem <: AbstractODESystem
     structure: structural information of the system
     """
     structure::Any
-    reduced_states::Vector
 end
 
 function ODESystem(
@@ -99,7 +98,7 @@ function ODESystem(
     if length(unique(sysnames)) != length(sysnames)
         throw(ArgumentError("System names must be unique."))
     end
-    ODESystem(deqs, iv′, dvs′, ps′, observed, tgrad, jac, Wfact, Wfact_t, name, systems, defaults, nothing, [])
+    ODESystem(deqs, iv′, dvs′, ps′, observed, tgrad, jac, Wfact, Wfact_t, name, systems, defaults, nothing)
 end
 
 iv_from_nested_derivative(x::Term) = operation(x) isa Differential ? iv_from_nested_derivative(arguments(x)[1]) : arguments(x)[1]

src/systems/nonlinear/nonlinearsystem.jl

@@ -43,7 +43,6 @@ struct NonlinearSystem <: AbstractSystem
     structure: structural information of the system
     """
     structure::Any
-    reduced_states::Any
 end
 
 function NonlinearSystem(eqs, states, ps;
@@ -58,7 +57,7 @@ function NonlinearSystem(eqs, states, ps;
     end
     defaults = todict(defaults)
     defaults = Dict(value(k) => value(v) for (k, v) in pairs(defaults))
-    NonlinearSystem(eqs, value.(states), value.(ps), observed, name, systems, defaults, nothing, [])
+    NonlinearSystem(eqs, value.(states), value.(ps), observed, name, systems, defaults, nothing)
 end
 
 function calculate_jacobian(sys::NonlinearSystem;sparse=false,simplify=false)

test/reduction.jl

@@ -80,7 +80,11 @@ connected = ODESystem([s ~ a + lorenz1.x
 # Reduced Flattened System
 
 reduced_system = structural_simplify(connected)
+reduced_system2 = structural_simplify(structural_simplify(structural_simplify(connected)))
 
+@test isempty(setdiff(states(reduced_system), states(reduced_system2)))
+@test isequal(equations(reduced_system), equations(reduced_system2))
+@test isequal(observed(reduced_system), observed(reduced_system2))
 @test setdiff(states(reduced_system), [
         s
         a