Remove unused cse keyword throughout ModelingToolkitBase

`cse` was threaded through the `*Function` constructors, `generate_*` helpers,
`build_function_wrapper`, `build_explicit_observed_function`, the SCC/optimal-
control/homotopy paths, and the `ObservedFunctionCache` (as a `Bool` field), but
nothing ever consumed it: it was only ever forwarded down to
`Symbolics.codegen_function`, which does not accept it (the IR codegen path has
no `cse` option). Common-subexpression elimination in the current pipeline is
unrelated to this flag.

Remove it everywhere in ModelingToolkitBase: constructor/helper keywords, the
`ObservedFunctionCache` field (and its constructor, `deepcopy`, and call
operator), and the documentation bullets. Symbolics' own `cse` (which *is* used
by `Symbolics.Code.cse`) is unaffected, as are the `##cse#` generated variable
names.

Constructors that take `kwargs...` remain backwards compatible (a stray `cse=`
is absorbed and dropped as before). The one exception is
`SymbolicIndexingInterface.observed`, which has no `kwargs...`: passing `cse=`
there now errors instead of being silently ignored.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: AayushSabharwal

lib/ModelingToolkitBase/src/problems/bvproblem.jl

@@ -1,6 +1,6 @@
 @fallback_iip_specialize function SciMLBase.BVProblem{iip, spec}(
         sys::System, op, tspan;
-        check_compatibility = true, cse = true,
+        check_compatibility = true,
         checkbounds = false, eval_expression = false, eval_module = @__MODULE__,
         expression = Val{false}, guesses = Dict(), callback = nothing,
         kwargs...
@@ -19,21 +19,21 @@
     fode, u0,
         p = process_SciMLProblem(
         ODEFunction{_iip, spec}, sys, _op; guesses,
-        t = tspan !== nothing ? tspan[1] : tspan, check_compatibility = false, cse,
+        t = tspan !== nothing ? tspan[1] : tspan, check_compatibility = false,
         checkbounds, time_dependent_init = false, expression, kwargs...
     )
 
     fcost = generate_bvp_cost(
         sys; expression = Val{false}, wrap_gfw = Val{false},
-        eval_expression, eval_module, cse, checkbounds
+        eval_expression, eval_module, checkbounds
     )
 
     stidxmap = Dict([v => i for (i, v) in enumerate(dvs)])
     u0_idxs = has_alg_eqs(sys) ? collect(1:length(dvs)) :
         [stidxmap[k] for (k, v) in op if haskey(stidxmap, k)]
     fbc = generate_boundary_conditions(
         sys, u0, u0_idxs, tspan[1]; expression = Val{false},
-        wrap_gfw = Val{true}, cse, checkbounds
+        wrap_gfw = Val{true}, checkbounds
     )
 
     n_controls = length(default_codegen_inputs(sys))

lib/ModelingToolkitBase/src/problems/daeproblem.jl

@@ -2,15 +2,15 @@
         sys::System; u0 = nothing, p = nothing, tgrad = false, jac = false,
         t = nothing, eval_expression = false, eval_module = @__MODULE__, sparse = false,
         steady_state = false, checkbounds = false, sparsity = false, analytic = nothing,
-        simplify = false, cse = true, initialization_data = nothing,
+        simplify = false, initialization_data = nothing,
         expression = Val{false}, check_compatibility = true, kwargs...
     ) where {iip, spec}
     check_complete(sys, DAEFunction)
     check_compatibility && check_compatible_system(DAEFunction, sys)
 
     f = generate_rhs(
         sys; expression, wrap_gfw = Val{true},
-        implicit_dae = true, eval_expression, eval_module, checkbounds = checkbounds, cse,
+        implicit_dae = true, eval_expression, eval_module, checkbounds = checkbounds,
         kwargs...
     )
 
@@ -28,15 +28,15 @@
     if jac
         _jac = generate_dae_jacobian(
             sys; expression,
-            wrap_gfw = Val{true}, simplify, sparse, cse, eval_expression, eval_module,
+            wrap_gfw = Val{true}, simplify, sparse, eval_expression, eval_module,
             checkbounds, kwargs...
         )
     else
         _jac = nothing
     end
 
     observedfun = ObservedFunctionCache(
-        sys; expression, steady_state, eval_expression, eval_module, checkbounds, cse
+        sys; expression, steady_state, eval_expression, eval_module, checkbounds
     )
 
     jac_prototype = if sparse

lib/ModelingToolkitBase/src/problems/ddeproblem.jl

@@ -1,15 +1,15 @@
 @fallback_iip_specialize function SciMLBase.DDEFunction{iip, spec}(
         sys::System; u0 = nothing, p = nothing, eval_expression = false,
         eval_module = @__MODULE__, expression = Val{false}, checkbounds = false,
-        initialization_data = nothing, cse = true, check_compatibility = true,
+        initialization_data = nothing, check_compatibility = true,
         sparse = false, simplify = false, analytic = nothing, kwargs...
     ) where {iip, spec}
     check_complete(sys, DDEFunction)
     check_compatibility && check_compatible_system(DDEFunction, sys)
 
     f = generate_rhs(
         sys; expression, wrap_gfw = Val{true},
-        eval_expression, eval_module, checkbounds = checkbounds, cse,
+        eval_expression, eval_module, checkbounds = checkbounds,
         kwargs...
     )
 
@@ -28,7 +28,7 @@
     _M = concrete_massmatrix(M; sparse, u0)
 
     observedfun = ObservedFunctionCache(
-        sys; expression, eval_expression, eval_module, checkbounds, cse
+        sys; expression, eval_expression, eval_module, checkbounds
     )
 
     kwargs = (;
@@ -45,7 +45,7 @@ end
 
 @fallback_iip_specialize function SciMLBase.DDEProblem{iip, spec}(
         sys::System, op, tspan;
-        callback = nothing, check_length = true, cse = true, checkbounds = false,
+        callback = nothing, check_length = true, checkbounds = false,
         eval_expression = false, eval_module = @__MODULE__, check_compatibility = true,
         u0_constructor = identity, expression = Val{false}, kwargs...
     ) where {iip, spec}
@@ -56,13 +56,13 @@ end
     f, u0,
         p = process_SciMLProblem(
         DDEFunction{_iip, spec}, sys, op;
-        t = tspan !== nothing ? tspan[1] : tspan, check_length, cse, checkbounds,
+        t = tspan !== nothing ? tspan[1] : tspan, check_length, checkbounds,
         eval_expression, eval_module, check_compatibility, symbolic_u0 = true,
         expression, u0_constructor, kwargs...
     )
 
     h = generate_history(
-        sys, u0; expression, wrap_gfw = Val{true}, cse, eval_expression, eval_module,
+        sys, u0; expression, wrap_gfw = Val{true}, eval_expression, eval_module,
         checkbounds
     )
 

lib/ModelingToolkitBase/src/problems/discreteproblem.jl

@@ -1,7 +1,7 @@
 @fallback_iip_specialize function SciMLBase.DiscreteFunction{iip, spec}(
         sys::System; u0 = nothing, p = nothing, t = nothing,
         eval_expression = false, eval_module = @__MODULE__, expression = Val{false},
-        checkbounds = false, analytic = nothing, simplify = false, cse = true,
+        checkbounds = false, analytic = nothing, simplify = false,
         initialization_data = nothing, check_compatibility = true,
         kwargs...
     ) where {iip, spec}
@@ -10,7 +10,7 @@
 
     f = generate_rhs(
         sys; expression, wrap_gfw = Val{true},
-        eval_expression, eval_module, checkbounds = checkbounds, cse,
+        eval_expression, eval_module, checkbounds = checkbounds,
         kwargs...
     )
 
@@ -26,8 +26,7 @@
     end
 
     observedfun = ObservedFunctionCache(
-        sys; steady_state = false, expression, eval_expression, eval_module, checkbounds,
-        cse
+        sys; steady_state = false, expression, eval_expression, eval_module, checkbounds
     )
 
     kwargs = (;

lib/ModelingToolkitBase/src/problems/docs.jl

@@ -248,7 +248,6 @@ function function_docstring(
     $EVAL_EXPR_MOD_KWARGS
     - `checkbounds`: Whether to enable bounds checking in the generated code.
     - `simplify`: Whether to `simplify` any symbolically computed jacobians/hessians/etc.
-    - `cse`: Whether to enable Common Subexpression Elimination (CSE) on the generated code.
       This typically improves performance of the generated code but reduces readability.
     - `sparse`: Whether to generate jacobian/hessian/etc. functions that return/operate on
       sparse matrices. Also controls whether the mass matrix is sparse, wherever applicable.
@@ -387,7 +386,6 @@ subtype indicating the level of specialization of the $func.
 $EVAL_EXPR_MOD_KWARGS
 - `checkbounds`: Whether to enable bounds checking in the generated code.
 - `simplify`: Whether to `simplify` any symbolically computed jacobians/hessians/etc.
-- `cse`: Whether to enable Common Subexpression Elimination (CSE) on the generated code.
   This typically improves performance of the generated code but reduces readability.
 - `fraction_cancel_fn`: The function to use to simplify fractions in the polynomial
   expression. A more powerful function can increase processing time but be able to

lib/ModelingToolkitBase/src/problems/implicitdiscreteproblem.jl

@@ -1,7 +1,7 @@
 @fallback_iip_specialize function SciMLBase.ImplicitDiscreteFunction{iip, spec}(
         sys::System; u0 = nothing, p = nothing, t = nothing, eval_expression = false,
         eval_module = @__MODULE__, expression = Val{false},
-        checkbounds = false, analytic = nothing, simplify = false, cse = true,
+        checkbounds = false, analytic = nothing, simplify = false,
         initialization_data = nothing, check_compatibility = true, kwargs...
     ) where {
         iip, spec,
@@ -13,7 +13,7 @@
     dvs = unknowns(sys)
     f = generate_rhs(
         sys; expression, wrap_gfw = Val{true},
-        implicit_dae = true, eval_expression, eval_module, checkbounds = checkbounds, cse,
+        implicit_dae = true, eval_expression, eval_module, checkbounds = checkbounds,
         override_discrete = true, kwargs...
     )
 
@@ -31,7 +31,7 @@
     end
 
     observedfun = ObservedFunctionCache(
-        sys; steady_state = false, expression, eval_expression, eval_module, checkbounds, cse
+        sys; steady_state = false, expression, eval_expression, eval_module, checkbounds
     )
 
     args = (; f)

lib/ModelingToolkitBase/src/problems/intervalnonlinearproblem.jl

@@ -1,20 +1,19 @@
 function SciMLBase.IntervalNonlinearFunction(
         sys::System; u0 = nothing, p = nothing, eval_expression = false,
         eval_module = @__MODULE__, expression = Val{false}, checkbounds = false,
-        analytic = nothing, cse = true, initialization_data = nothing,
+        analytic = nothing, initialization_data = nothing,
         check_compatibility = true, kwargs...
     )
     check_complete(sys, IntervalNonlinearFunction)
     check_compatibility && check_compatible_system(IntervalNonlinearFunction, sys)
 
     f = generate_rhs(
         sys; expression, wrap_gfw = Val{true},
-        scalar = true, eval_expression, eval_module, checkbounds, cse, kwargs...
+        scalar = true, eval_expression, eval_module, checkbounds, kwargs...
     )
 
     observedfun = ObservedFunctionCache(
-        sys; steady_state = false, expression, eval_expression, eval_module, checkbounds,
-        cse
+        sys; steady_state = false, expression, eval_expression, eval_module, checkbounds
     )
 
     args = (; f)

lib/ModelingToolkitBase/src/problems/jumpproblem.jl

@@ -1,7 +1,7 @@
 @fallback_iip_specialize function JumpProcesses.JumpProblem{iip, spec}(
         sys::System, op, tspan::Union{Tuple, Nothing};
         check_compatibility = true, eval_expression = false, eval_module = @__MODULE__,
-        checkbounds = false, cse = true, aggregator = JumpProcesses.NullAggregator(),
+        checkbounds = false, aggregator = JumpProcesses.NullAggregator(),
         callback = nothing, rng = nothing, save_positions = (true, true), kwargs...
     ) where {iip, spec}
     check_complete(sys, JumpProblem)
@@ -23,13 +23,13 @@
         if has_eqs && has_noise
             prob = SDEProblem{iip, spec}(
                 sys, op, tspan; check_compatibility = false,
-                build_initializeprob = false, checkbounds, cse, check_length = false,
+                build_initializeprob = false, checkbounds, check_length = false,
                 _skip_events = true, _skip_tstops = true, kwargs...
             )
         elseif has_eqs
             prob = ODEProblem{iip, spec}(
                 sys, op, tspan; check_compatibility = false,
-                build_initializeprob = false, checkbounds, cse, check_length = false,
+                build_initializeprob = false, checkbounds, check_length = false,
                 _skip_events = true, _skip_tstops = true, kwargs...
             )
         else
@@ -41,7 +41,7 @@
             )
             observedfun = ObservedFunctionCache(
                 sys; eval_expression, eval_module,
-                checkbounds, cse
+                checkbounds
             )
             f = (du, u, p, t) -> (du .= 0; nothing)
             df = ODEFunction{true, spec}(f; sys, observed = observedfun)
@@ -51,12 +51,12 @@
         _f, u0,
             p = process_SciMLProblem(
             EmptySciMLFunction{iip}, sys, op;
-            t = tspan === nothing ? nothing : tspan[1], check_length = false, build_initializeprob = false, cse, kwargs...
+            t = tspan === nothing ? nothing : tspan[1], check_length = false, build_initializeprob = false, kwargs...
         )
         f = DiffEqBase.DISCRETE_INPLACE_DEFAULT
 
         observedfun = ObservedFunctionCache(
-            sys; eval_expression, eval_module, checkbounds, cse
+            sys; eval_expression, eval_module, checkbounds
         )
 
         df = DiscreteFunction{true, true}(

lib/ModelingToolkitBase/src/problems/linearproblem.jl

@@ -22,7 +22,7 @@ Moshi.Derive.@derive StructuralHint[Show]
 function LinearFunction{iip}(
         sys::System; expression = Val{false}, check_compatibility = true,
         sparse = false, eval_expression = false, eval_module = @__MODULE__,
-        checkbounds = false, cse = true,
+        checkbounds = false,
         structural_hint::StructuralHint.Type = StructuralHint.NoHint(), kwargs...
     ) where {iip}
     check_complete(sys, LinearProblem)
@@ -39,15 +39,14 @@ function LinearFunction{iip}(
     end
     update_A = generate_update_A(
         sys, A; expression, wrap_gfw = Val{true}, eval_expression,
-        eval_module, checkbounds, cse, kwargs...
+        eval_module, checkbounds, kwargs...
     )
     update_b = generate_update_b(
         sys, b; expression, wrap_gfw = Val{true}, eval_expression,
-        eval_module, checkbounds, cse, kwargs...
+        eval_module, checkbounds, kwargs...
     )
     observedfun = ObservedFunctionCache(
-        sys; steady_state = false, expression, eval_expression, eval_module, checkbounds,
-        cse
+        sys; steady_state = false, expression, eval_expression, eval_module, checkbounds
     )
 
     if expression == Val{true}

lib/ModelingToolkitBase/src/problems/nonlinearproblem.jl

@@ -2,7 +2,7 @@
         sys::System; u0 = nothing, p = nothing, jac = false,
         eval_expression = false, eval_module = @__MODULE__, sparse = false,
         checkbounds = false, sparsity = false, analytic = nothing,
-        simplify = false, cse = true, initialization_data = nothing,
+        simplify = false, initialization_data = nothing,
         resid_prototype = nothing, check_compatibility = true, expression = Val{false},
         kwargs...
     ) where {iip, spec}
@@ -11,7 +11,7 @@
 
     f = generate_rhs(
         sys; expression, wrap_gfw = Val{true},
-        eval_expression, eval_module, checkbounds = checkbounds, cse,
+        eval_expression, eval_module, checkbounds = checkbounds,
         kwargs...
     )
 
@@ -29,16 +29,15 @@
     if jac
         _jac = generate_jacobian(
             sys; expression,
-            wrap_gfw = Val{true}, simplify, sparse, cse, eval_expression, eval_module,
+            wrap_gfw = Val{true}, simplify, sparse, eval_expression, eval_module,
             checkbounds, kwargs...
         )
     else
         _jac = nothing
     end
 
     observedfun = ObservedFunctionCache(
-        sys; steady_state = false, expression, eval_expression, eval_module, checkbounds,
-        cse
+        sys; steady_state = false, expression, eval_expression, eval_module, checkbounds
     )
 
     if sparse