Negate the W operator

Author: YingboMa

src/systems/diffeqs/diffeqsystem.jl

@@ -126,14 +126,14 @@ function generate_factorized_W(sys::ODESystem, simplify=true; version::FunctionV
 
     gam = Variable(:gam; known = true)()
 
-    W = LinearAlgebra.I - gam*jac
+    W = - LinearAlgebra.I + gam*jac
     Wfact = lu(W, Val(false), check=false).factors
 
     if simplify
         Wfact = simplify_constants.(Wfact)
     end
 
-    W_t = LinearAlgebra.I/gam - jac
+    W_t = - LinearAlgebra.I/gam + jac
     Wfact_t = lu(W_t, Val(false), check=false).factors
     if simplify
         Wfact_t = simplify_constants.(Wfact_t)

test/system_construction.jl

@@ -62,13 +62,13 @@ Sfw = fw(u, p, 0.2, 0.1)
 @test Sfw.U ≈ UpperTriangular(FW)
 sol = Sfw \ @SArray ones(3)
 @test sol isa SArray
-@test sol ≈ (I - 0.2*J)\ones(3)
+@test sol ≈ -(I - 0.2*J)\ones(3)
 Sfw_t = fwt(u, p, 0.2, 0.1)
 @test Sfw_t.L ≈ UnitLowerTriangular(FWt)
 @test Sfw_t.U ≈ UpperTriangular(FWt)
 sol = Sfw_t \ @SArray ones(3)
 @test sol isa SArray
-@test sol ≈ (I/0.2 - J)\ones(3)
+@test sol ≈ -(I/0.2 - J)\ones(3)
 
 @testset "time-varying parameters" begin
     @parameters σ′(t-1)