From 358334a8938d1d11dafe260de043b86a9490b254 Mon Sep 17 00:00:00 2001
From: Mike J Innes <mike.j.innes@gmail.com>
Date: Wed, 19 Apr 2017 17:13:57 +0100
Subject: [PATCH] mxnet back! for multi outputs

---
 src/backend/mxnet/model.jl | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/backend/mxnet/model.jl b/src/backend/mxnet/model.jl
index 904b90dd..11c6db60 100644
--- a/src/backend/mxnet/model.jl
+++ b/src/backend/mxnet/model.jl
@@ -46,6 +46,12 @@ mxgroup(x::Tuple) = mx.Group(mxgroup.(x)...)
 mxungroup(x, outs) = copy(shift!(outs))
 mxungroup(x::Tuple, outs) = map(x -> mxungroup(x, outs), x)
 
+function collectt(xs)
+  ys = []
+  mapt(x -> push!(ys, x), xs)
+  return ys
+end
+
 function dictt(ks::Tuple, vs, d = Dict())
   for i = 1:length(ks)
     dictt(ks[i], vs[i], d)
@@ -75,7 +81,7 @@ end
 
 function Flux.back!(exec::Exec, Δ)
   mapt(k -> exec.grads[k][:] = 0, exec.graph.input)
-  mx.backward(exec.exec, MXArray(Δ).data)
+  mx.backward(exec.exec, map(x -> MXArray(x).data, collectt(Δ)))
   mapt(k -> copy(exec.grads[k]), exec.graph.input)
 end