Handle the u0 === nothing case

Co-authored-by: "Chris Rackauckas" <[email protected]>

Author: YingboMa

src/systems/diffeqs/abstractodesystem.jl

@@ -244,8 +244,13 @@ function process_DEProblem(constructor, sys::AbstractODESystem,u0map,parammap;
                            kwargs...)
     dvs = states(sys)
     ps = parameters(sys)
-    u0map′ = lower_mapnames(u0map,get_iv(sys))
-    u0 = varmap_to_vars(u0map′,dvs; defaults=default_u0(sys))
+
+    if u0map !== nothing
+        u0map′ = lower_mapnames(u0map,get_iv(sys))
+        u0 = varmap_to_vars(u0map′,dvs; defaults=default_u0(sys))
+    else
+        u0 = nothing
+    end
 
     if !(parammap isa DiffEqBase.NullParameters)
         parammap′ = lower_mapnames(parammap)

src/systems/diffeqs/sdesystem.jl

@@ -369,7 +369,8 @@ function SDEProblemExpr{iip}(sys::SDESystem,u0map,tspan,
         I,J,V = findnz(SparseArrays.sparse(noiseeqs))
         noise_rate_prototype = SparseArrays.sparse(I,J,zero(eltype(u0)))
     else
-        noise_rate_prototype = zeros(eltype(u0),size(noiseeqs))
+        T = u0 === nothing ? Float64 : eltype(u0)
+        noise_rate_prototype = zeros(T,size(get_noiseeqs(sys)))
     end
     ex = quote
         f = $f

test/sdesystem.jl

@@ -28,6 +28,9 @@ solexpr = solve(eval(probexpr),SRIW1(),seed=1)
 
 @test all(x->x==0,Array(sol-solexpr))
 
+# Test no error
+SDEProblem(de,nothing,nothing,SciMLBase.NullParameters())
+
 noiseeqs_nd = [0.01*x 0.01*x*y 0.02*x*z
                σ      0.01*y   0.02*x*z
                ρ      β        0.01*z  ]