Merge pull request #176 from devmotion/fix_forwarddiff_interpolant

Enable autodifferentiation of in-place interpolants

src/dense/generic_dense.jl

@@ -322,10 +322,17 @@ function ode_addsteps!{calcVal,calcVal2,calcVal3}(k,t,uprev,u,dt,f,cache,always_
 end
 
 @inline function ode_interpolant{TI}(Θ,dt,y₀,y₁,k,cache::OrdinaryDiffEqMutableCache,idxs,T::Type{Val{TI}})
+  # determine output type
+  # required for calculation of time derivatives with autodifferentiation
+  oneunit_Θ = oneunit(Θ)
+  S = promote_type(typeof(oneunit_Θ * oneunit(eltype(y₀))), # Θ*y₀
+                   typeof(oneunit_Θ * oneunit(eltype(y₁))), # Θ*y₁
+                   typeof(oneunit_Θ * oneunit(dt) * oneunit(eltype(k[1])))) # Θ*dt*k
+
   if typeof(idxs) <: Void
-    out = similar(y₀)
+    out = similar(y₀, S)
   else
-    !(typeof(idxs) <: Number) && (out = similar(y₀,indices(idxs)))
+    !(typeof(idxs) <: Number) && (out = similar(y₀, S, indices(idxs)))
   end
   if typeof(idxs) <: Number
     return ode_interpolant!(nothing,Θ,dt,y₀,y₁,k,cache,idxs,T)