cleaner

Author: MasonProtter

src/systems/systems.jl

@@ -130,8 +130,10 @@ function __structural_simplify(sys::AbstractSystem, io = nothing; simplify = fal
         # Fix for https://github.com/SciML/ModelingToolkit.jl/issues/2490
         noise_eqs = if all(row -> count(!iszero, row) == 1, eachrow(sorted_g_rows)) # Does each row have only one non-zero entry?
             # then the noise is actually diagonal! make vector of non-zero entries.
-            # This happens when the user uses N different `@brownian`s for `N` equations
-            reduce(vcat, map(row -> filter(!iszero, row), eachrow(sorted_g_rows)))
+            # This happens when the user uses multiple `@brownian`s but never mixes them
+            map(eachrow(sorted_g_rows)) do row
+                only(filter(!iszero, row))
+            end
         elseif sorted_g_rows isa AbstractMatrix && size(sorted_g_rows, 2) == 1
             sorted_g_rows[:, 1] # Take a vector slice so solver knows there's no mixing
         else