[GRAPH] Include default metadata description in graph. (#2770)

python/tvm/relay/backend/graph_runtime_codegen.py

@@ -20,7 +20,7 @@ contrib.graph_runtime or any other TVM runtime comptatible system.
 
 from __future__ import absolute_import
 import json
-from collections import defaultdict
+from collections import defaultdict, OrderedDict
 import attr
 from . import _backend
 from . import compile_engine
@@ -348,13 +348,31 @@ class GraphRuntimeCodegen(ExprFunctor):
             attrs["device_index"] = ["list_int", device_types]
         attrs["dltype"] = ["list_str", dltypes]
 
-        json_dict = {
+        # Metadata definitions
+        def nested_defaultdict():
+            return defaultdict(nested_defaultdict)
+        metadata = nested_defaultdict()
+        for node_id in arg_nodes:
+            node_name = nodes[node_id]['name']
+            if node_name not in self.params:
+                metadata['signatures']['default']['inputs'][node_name]['id'] = node_id
+                metadata['signatures']['default']['inputs'][node_name]['dtype'] = dltypes[node_id]
+                metadata['signatures']['default']['inputs'][node_name]['shape'] = shapes[node_id]
+        for node_id in heads:
+            node_name = nodes[node_id[0]]['name']
+            metadata['signatures']['default']['outputs'][node_name]['id'] = node_id[0]
+            metadata['signatures']['default']['outputs'][node_name]['dtype'] = dltypes[node_id[0]]
+            metadata['signatures']['default']['outputs'][node_name]['shape'] = shapes[node_id[0]]
+
+        # Keep  'metadata' always at end
+        json_dict = OrderedDict({
             "nodes": nodes,
             "arg_nodes": arg_nodes,
             "heads": heads,
             "attrs": attrs,
-            "node_row_ptr":  node_row_ptr
-        }
+            "node_row_ptr":  node_row_ptr,
+            "metadata": metadata
+        })
 
         return json.dumps(json_dict, indent=2)
 

src/runtime/graph/graph_runtime.h

@@ -318,6 +318,8 @@ class GraphRuntime : public ModuleNode {
         } else if (key == "attrs") {
           reader->Read(&attrs_);
           bitmask |= 16;
+        } else if (key == "metadata") {
+          break;
         } else {
           LOG(FATAL) << "key " << key << " is not supported";
         }