use interpreter for forward pass

src/Flux.jl

@@ -4,7 +4,7 @@ using MacroTools, Lazy, DataFlow, Juno
 using DataFlow: graphm, syntax, prewalk!, postwalk!, prewalk, postwalk,
   iscyclic, Constant, constant, isconstant, Group, group, Split, splitnode,
   detuple, value, inputs, thread!, value, inputs, Split, splitnode, inputnode,
-  spliceinputs, bumpinputs
+  spliceinputs, bumpinputs, interpret
 using Juno: Tree, Row
 
 # Zero Flux Given

src/compiler/code.jl

@@ -34,35 +34,10 @@ function build_type(T, params)
   ex
 end
 
-function deref_params(v)
-  map(v) do x
-    isa(x, Constant) && @capture(x.value, self.p_) ? Constant(:(state(self.$p))) : x
-  end
-end
-
-function build_forward(body, args)
-  iscyclic(body) && return :(error("Can't run forward pass on a cyclic graph"))
-  syntax(cse(deref_params(body)))
-end
-
-function build_backward(body, x, params = [])
-  iscyclic(body) && return :(error("Can't run backward pass on a cyclic graph"))
-  Δs = invert(body)
-  back = IVertex{Any}(DataFlow.Do())
-  for param in params
-    haskey(Δs, :(self.$param)) || continue
-    ex = Δs[:(self.$param)]
-    ex = deref_params(ex)
-    thread!(back, @vtx(accumulate!(:(self.$param), ex)))
-  end
-  ex = Δs[x]
-  ex = deref_params(ex)
-  thread!(back, @flow(tuple($ex)))
-  syntax(cse(back))
-end
-
 import Lazy: groupby
 
+reifyparams(v::IVertex) = mapconst(x -> isa(x, Param) ? x.x : x, v)
+
 function process_type(ex)
   @capture(ex, type T_ fs__ end)
   @destruct [params = false || [],
@@ -73,8 +48,7 @@ function process_type(ex)
   @assert length(args) == 1
   quote
     $(build_type(T, params))
-    (self::$T)($(args...),) = $(build_forward(body, args))
-    back!(self::$T, Δ, $(args...)) = $(build_backward(body, args[1], pnames))
+    (self::$T)($(args...),) = interpret(reifyparams(graph(self)), $(args...))
     update!(self::$T, η) = $(map(p -> :(update!(self.$p, η)), pnames)...)
     graph(self::$T) = $(DataFlow.constructor(makegraph(body, args)))
     nothing