From f52b0140a50589267a6000d6a3e6921b95f04474 Mon Sep 17 00:00:00 2001
From: Mike J Innes <mike.j.innes@gmail.com>
Date: Sat, 13 Aug 2016 00:33:39 +0100
Subject: [PATCH] remove loop compilation

---
 src/Flux.jl          |  1 -
 src/compiler/code.jl | 20 +--------------
 src/compiler/loop.jl | 59 --------------------------------------------
 3 files changed, 1 insertion(+), 79 deletions(-)
 delete mode 100644 src/compiler/loop.jl

diff --git a/src/Flux.jl b/src/Flux.jl
index bee668ec..c48d4855 100644
--- a/src/Flux.jl
+++ b/src/Flux.jl
@@ -15,7 +15,6 @@ update!(m::Model, η) = m
 include("capacitor.jl")
 
 include("compiler/diff.jl")
-include("compiler/loop.jl")
 include("compiler/code.jl")
 
 include("cost.jl")
diff --git a/src/compiler/code.jl b/src/compiler/code.jl
index 188b9116..335c7b71 100644
--- a/src/compiler/code.jl
+++ b/src/compiler/code.jl
@@ -17,27 +17,20 @@ function build_type(T, params)
 end
 
 function build_forward(body, args)
-  body = cut_forward(body, args)
   cse(body)
 end
 
 function build_backward(body, x, params)
-  Δs, Δloops = cut_backward(body, [x])
+  Δs = invert(body)
   back = IVertex{Any}(Flow.Do())
   for param in params
     haskey(Δs, :(self.$param)) || continue
     k = symbol("Δ", param)
     ksym = Expr(:quote, k)
     ex = Δs[:(self.$param)]
-    for Δloop in Δloops
-      ex = addΔ(ex, get(Δloop, :(self.$param), vertex(0)))
-    end
     thread!(back, @v(setfield!(:self, ksym, :(self.$k) + ex)))
   end
   ex = Δs[x]
-  for Δloop in Δloops
-    ex = addΔ(ex, get(Δloop, x, vertex(0)))
-  end
   thread!(back, @flow(tuple($ex)))
   cse(back)
 end
@@ -69,16 +62,5 @@ end
 # process_type(:(type Sigmoid
 #   W
 #   b
-#   bp
 #   x -> σ(W*x+b)
 # end)) |> prettify
-
-process_type(:(type Recurrent
-  Wxh; Whh; Bh
-  Why; By
-
-  function (x)
-    hidden = σ( Wxh*x + Whh*Delay(hidden) + Bh )
-    y = σ( Why*hidden + By )
-  end
-end)) |> prettify
diff --git a/src/compiler/loop.jl b/src/compiler/loop.jl
deleted file mode 100644
index 91c02deb..00000000
--- a/src/compiler/loop.jl
+++ /dev/null
@@ -1,59 +0,0 @@
-function delays(v::IVertex)
-  ds = []
-  Flow.prefor(v) do w
-    value(w) == :Delay &&
-      push!(ds, w)
-  end
-  return ds
-end
-
-function cut(v::IVertex, f = _ -> il(@flow(last(self.delay))))
-  prewalk(v) do v
-    value(v) == :Delay ? f(v) : v
-  end
-end
-
-replaceall(d::Dict, args...) = Dict(k => replace(v, args...) for (k, v) in d)
-
-# Create the forward function; a single delay node becomes an
-# input and an output node.
-function cut_forward(v::IVertex, params, ds = delays(v))
-  pushes = map(x->vertex(:push!, vertex(:(self.delay)), x[1], map(vertex, params)...), ds)
-  isempty(pushes) && return v
-  @assert length(pushes) == 1
-  v = vertex(Flow.Do(), pushes..., v)
-  cut(v)
-end
-
-# Given a delay node, give the parameter gradients with respect to
-# the node and a function which will propagate gradients around
-# the loop.
-function invertloop(v::IVertex, params)
-  @gensym input
-  v = cut(v[1], v -> vertex(input))
-  Δs = invert(v, @flow(Δloop))
-  Δs = replaceall(Δs, vertex(input), il(@flow(last(self.delay))))
-  Δs, :((Δ, $input, $(params...)) -> $(syntax(cse(Δs[input]))))
-end
-
-# Returns:
-#   Parameter gradients with respect to the function
-#   Parameter gradients with respect to each delay node
-function cut_backward(v::IVertex, params, ds = delays(v))
-  isempty(ds) && return invert(v), []
-  @assert length(ds) == 1
-  @gensym input
-  Δs = invert(cut(v, _ -> vertex(input)))
-  Δs = replaceall(Δs, vertex(input), il(@flow(last(self.delay))))
-  Δloop, ∇loop = invertloop(ds[1], params)
-  Δh = vertex(:back!, vertex(:(self.delay)), Δs[input], vertex(∇loop))
-  Δloop = replaceall(Δloop, vertex(:Δloop), Δh)
-  Δs, [Δloop]
-end
-
-# g = il(@flow begin
-#   hidden = σ( Wxh*x + Whh*Delay(hidden) + bh )
-#   y = σ( Why*hidden + by )
-# end)
-
-# cut_backward(g, [:x])[1]