fix restore layout in AlterOpLayout (#460)

* fix restore layout in AlterOpLayout

* lint test case

nnvm/src/compiler/alter_op_layout.cc

@@ -119,8 +119,9 @@ Graph AlterOpLayout(const Graph& src) {
       if (new_nodes.count(inode.source)) {
         const std::vector<Layout>& in_layouts =
           in_layouts_of_node[new_nodes[inode.source]];
-        for (const auto& e : inode.inputs) {
-          ret_layouts[ret_idx.entry_id(e)] = in_layouts[e.index];
+        for (uint32_t i = 0; i < inode.inputs.size(); ++i) {
+          const auto& e = inode.inputs[i];
+          ret_layouts[ret_idx.entry_id(e)] = in_layouts[i];
         }
         const std::vector<Layout>& out_layouts =
           out_layouts_of_node[new_nodes[inode.source]];

nnvm/tests/python/compiler/test_alter_op_layout.py

@@ -19,10 +19,14 @@ def test_alter_conv2d_layout():
     conv = sym.conv2d(data, name="conv", channels=16,
                       kernel_size=(3,3), padding=(1,1),
                       use_bias=False, layout="NCHW")
-    relu = sym.relu(conv, name="relu")
+    # split here
+    convs = sym.split(conv, indices_or_sections=2)
+    relus = [sym.relu(x, name="relu") for x in convs]
+    relu = sym.concatenate(*relus)
     flatten = sym.flatten(relu, name="flatten")
     softmax = sym.softmax(flatten, name="softmax")
     g = graph.create(softmax)
+
     g = g.apply("CorrectLayout")
     g = graph_attr.set_dtype_inputs(g, "float32")
     g = g.apply(["InferShape", "InferType"])