so can unseq

src/compiler/loops.jl

@@ -60,9 +60,7 @@ end
 
 hiddeninput(n) = vertex(Split(n), inputnode(1))
 
-function create_steps(v::IVertex, n; seq = true)
+create_steps(v::IVertex, n) = [bumpinputs(spliceinputs(v, hiddeninput(i))) for i = 1:n]
-  [copy(seq ? spliceinputs(v, hiddeninput(i)) : v) for i = 1:n]
-end
 
 function getvar(n, step, steps, offset, default)
   if step < 1
@@ -86,13 +84,11 @@ end
 
 # Input:  (hidden1, hidden2, ...), (x1, x2, ...)
 # Output: (hidden1, hidden2, ...), (y1, y2, ...)
-# If `seq` is false, takes a single `x` and uses this for each iteration.
-# If `stateful` is false there are no hidden inputs or outputs.
 
-function unrollgraph(v::IVertex, n; seq = true)
+function unrollgraph(v::IVertex, n)
   state, offset, default = collect_state(v)
   v = group(group(state...), v)
-  steps = create_steps(v, n, seq = seq)
+  steps = create_steps(v, n)
   for i = 1:n
     vars = inputs(steps[i][1])
     postwalk!(steps[i]) do v
@@ -121,13 +117,21 @@ end
 
 graph(u::Unrolled) = u.graph
 
-function unroll(model, n; seq = true)
+function unroll(model, n)
-  graph, state = unrollgraph(model, n; seq = seq)
+  graph, state = unrollgraph(model, n)
   Unrolled(model, graph, state, true, n)
 end
 
+function unseqinput(v::IVertex)
+  prewalk(v) do v
+    # TODO: inputidx function
+    isa(value(v), Split) && DataFlow.isinput(v[1]) && value(v[1]).n == 2 ? v[1] : v
+  end
+end
+
 function unroll1(model)
-  graph, state = unrollgraph(model, 1; seq = false)
+  graph, state = unrollgraph(model, 1)
+  graph = unseqinput(graph)
   graph = group(graph[1], map(x->x[1], inputs(graph)[2:end])...)
   Unrolled(model, graph, state, false, 1)
 end