Merge pull request #1477 from xtalax/sparseMM

Check against Identity with equality

Author: ChrisRackauckas

src/systems/diffeqs/abstractodesystem.jl

@@ -279,7 +279,7 @@ function calculate_massmatrix(sys::AbstractODESystem; simplify=false)
     end
     M = simplify ? ModelingToolkit.simplify.(M) : M
     # M should only contain concrete numbers
-    M === I ? I : M
+    M == I ? I : M
 end
 
 function jacobian_sparsity(sys::AbstractODESystem)

test/mass_matrix.jl

@@ -1,4 +1,4 @@
-using OrdinaryDiffEq, ModelingToolkit, Test
+using OrdinaryDiffEq, ModelingToolkit, Test, LinearAlgebra
 @parameters t
 @variables y[1:3](t)
 @parameters k[1:3]
@@ -34,3 +34,10 @@ sol2 = solve(prob_mm2,Rodas5(),reltol=1e-8,abstol=1e-8,tstops=sol.t,adaptive=fal
 # MTK expression are canonicalized, so the floating point numbers are slightly
 # different
 @test Array(sol) ≈ Array(sol2)
+
+# Test mass matrix in the identity case
+eqs = [D(y[1]) ~ y[1], D(y[2]) ~ y[2], D(y[3]) ~ y[3]]
+
+@named sys = ODESystem(eqs,t,y,k)
+
+@test calculate_massmatrix(sys) === I

test/odesystem.jl

@@ -358,7 +358,7 @@ D = Differential(t)
 eqs = [D(x1) ~ -x1]
 @named sys = ODESystem(eqs,t,[x1,x2],[])
 @test_throws ArgumentError ODEProblem(sys, [1.0,1.0], (0.0,1.0))
-@test_throws DimensionMismatch ODEProblem(sys, [1.0,1.0], (0.0,1.0), check_length=false)
+@test_nowarn ODEProblem(sys, [1.0,1.0], (0.0,1.0), check_length=false) 
 
 # check inputs
 let