model storage notes

docs/make.jl

@@ -14,7 +14,8 @@ makedocs(modules=[Flux],
                     "Debugging"             => "models/debugging.md"],
                   "Other APIs" => [
                     "Batching" => "apis/batching.md",
-                    "Backends" => "apis/backends.md"],
+                    "Backends" => "apis/backends.md",
+                    "Storing Models" => "apis/storage.md"],
                   "In Action" => [
                     "Logistic Regression" => "examples/logreg.md",
                     "Char RNN" => "examples/char-rnn.md"],

docs/src/apis/storage.md

@@ -0,0 +1,24 @@
+# Loading and Save Models
+
+```julia
+model = Chain(Affine(10, 20), σ, Affine(20, 15), softmax)
+```
+
+Since models are just simple Julia data structures, it's very easy to save and load them using any of Julia's existing serialisation formats. For example, using Julia's built-in `serialize`:
+
+```julia
+open(io -> serialize(io, model), "model.jls", "w")
+open(io -> deserialize(io), "model.jls")
+```
+
+One issue with `serialize` is that it doesn't promise compatibility between major Julia versions. For longer-term storage it's good to use a package like [JLD](https://github.com/JuliaIO/JLD.jl).
+
+```julia
+using JLD
+@save "model.jld" model
+@load "model.jld"
+```
+
+However, JLD will break for some models as functions are not supported on 0.5+. You can resolve that by checking out [this branch](https://github.com/JuliaIO/JLD.jl/pull/137).
+
+Right now this is the only storage format Flux supports. In future Flux will support loading and saving other model formats (on an as-needed basis).

src/layers/chain.jl

@@ -20,7 +20,7 @@ type Chain <: Model
   end
 end
 
-@forward Chain.layers Base.getindex, Base.first, Base.last
+@forward Chain.layers Base.getindex, Base.first, Base.last, Base.endof
 
 (s::Chain)(x) = foldl((x, m) -> m(x), x, s.layers)
 back!(s::Chain, Δ) = foldr((m, Δ) -> back!(m, Δ), Δ, s.layers)
@@ -30,3 +30,5 @@ graph(s::Chain) =
   foldl((v, m) -> vertex(m, v), constant(inputnode(1)), s.layers)
 
 shape(c::Chain, in) = c.shape
+
+Base.getindex(c::Chain, i::AbstractArray) = Chain(c.layers[i])