actually get GRU working

src/backend/tensorflow/graph.jl

@@ -2,14 +2,18 @@ import Base: @get!
 import DataFlow: Constant, postwalk, value, inputs, constant
 import TensorFlow: RawTensor
 
+# TODO: implement Julia's type promotion rules
+
 cvalue(x) = x
 cvalue(c::Constant) = c.value
 cvalue(v::Vertex) = cvalue(value(v))
 
 graph(x::Tensor) = x
+graph(x::Number) = TensorFlow.constant(Float32(x))
 
 graph(::typeof(*), args...) = *(args...)
 graph(::typeof(.*), args...) = .*(args...)
+graph(::typeof(.-), args...) = -(args...)
 graph(::typeof(+), args...) = +(args...)
 graph(::typeof(softmax), x) = nn.softmax(x)
 graph(::typeof(relu), x) = nn.relu(x)

src/layers/recurrent.jl

@@ -1,4 +1,4 @@
-export Recurrent, LSTM
+export Recurrent, GatedRecurrent, LSTM
 
 @net type Recurrent
   Wxy; Wyy; by
@@ -11,6 +11,23 @@ end
 Recurrent(in, out; init = initn) =
   Recurrent(init((in, out)), init((out, out)), init(out), init(out))
 
+@net type GatedRecurrent
+  Wxr; Wyr; br
+  Wxu; Wyu; bu
+  Wxh; Wyh; bh
+  y
+  function (x)
+    reset  = σ( x * Wxr + y * Wyr + br )
+    update = σ( x * Wxu + y * Wyu + bu )
+    y′ = tanh( x * Wxh + (reset .* y) * Wyh + bh )
+    y = (1 .- update) .* y′ + update .* y
+  end
+end
+
+GatedRecurrent(in, out; init = initn) =
+  GatedRecurrent(vcat([[init((in, out)), init((out, out)), init(out)] for _ = 1:3]...)...,
+       zeros(Float32, out))
+
 @net type LSTM
   Wxf; Wyf; bf
   Wxi; Wyi; bi
@@ -32,20 +49,3 @@ end
 LSTM(in, out; init = initn) =
   LSTM(vcat([[init((in, out)), init((out, out)), init(out)] for _ = 1:4]...)...,
        zeros(Float32, out), zeros(Float32, out))
-
-@net type GatedRecurrent
-  Wxr; Wyr; br
-  Wxu; Wyu; bu
-  Wxh; Wyh; bh
-  state
-  function (x)
-    reset  = σ( x * Wxr + y * Wyr + br )
-    update = σ( x * Wxu + y * Wyu + bu )
-    state′ = tanh( x * Wxh + (reset .* y) * Wyh + bh )
-    state = (1 .- update) .* state′ + update .* y
-  end
-end
-
-GatedRecurrent(in, out; init = initn) =
-  GatedRecurrent(vcat([[init((in, out)), init((out, out)), init(out)] for _ = 1:3]...)...,
-       zeros(Float32, out))