[Hetero][RFC] Heterogeneous graph Python interfaces & Message Passing (…

…dmlc#752)

* moving heterograph index to another file

* node view

* python interfaces

* heterograph init

* bug fixes

* docstring for readonly

* more docstring

* unit tests & lint

* oops

* oops x2

* removed node/edge addition

* addressed comments

* lint

* rw on frames with one node/edge type

* homograph with underlying heterograph demo

* view is not necessary

* bugfix

* replace

* scheduler, builtins not working yet

* moving bipartite.h to header

* moving back bipartite to bipartite.h

* oops

* asbits and copyto for bipartite

* tested update_all and send_and_recv

* lightweight node & edge type retrieval

* oops

* sorry

* removing obsolete code

* oops

* lint

* various bug fixes & more tests

* UDF tests

* multiple type number_of_nodes and number_of_edges

* docstring fixes

* more tests

* going for dict in initialization

* lint

* updated api as per discussions

* lint

* bug

* bugfix

* moving back bipartite impl to cc

* note on views

* fix

include/dgl/array.h

@@ -116,6 +116,11 @@ IdArray IndexSelect(IdArray array, IdArray index);
  */
 IdArray Relabel_(const std::vector<IdArray>& arrays);
 
+/*!\brief Return whether the array is a valid 1D int array*/
+inline bool IsValidIdArray(const dgl::runtime::NDArray& arr) {
+  return arr->ndim == 1 && arr->dtype.code == kDLInt;
+}
+
 //////////////////////////////////////////////////////////////////////
 // Sparse matrix
 //////////////////////////////////////////////////////////////////////

python/dgl/__init__.py

@@ -17,6 +17,7 @@
 from .backend import load_backend
 from .batched_graph import *
 from .graph import DGLGraph
+from .heterograph import DGLHeteroGraph
 from .nodeflow import *
 from .traversal import *
 from .transform import *

python/dgl/graph.py

@@ -49,6 +49,14 @@ def number_of_nodes(self):
         """
         return self._graph.number_of_nodes()
 
+    def _number_of_src_nodes(self):
+        """Return number of source nodes (only used in scheduler)"""
+        return self.number_of_nodes()
+
+    def _number_of_dst_nodes(self):
+        """Return number of destination nodes (only used in scheduler)"""
+        return self.number_of_nodes()
+
     def __len__(self):
         """Return the number of nodes in the graph."""
         return self.number_of_nodes()
@@ -65,6 +73,10 @@ def is_readonly(self):
         """
         return self._graph.is_readonly()
 
+    def _number_of_edges(self):
+        """Return number of edges in the current view (only used for scheduler)"""
+        return self.number_of_edges()
+
     def number_of_edges(self):
         """Return the number of edges in the graph.
 
@@ -939,6 +951,14 @@ def _get_msg_index(self):
     def _set_msg_index(self, index):
         self._msg_index = index
 
+    @property
+    def _src_frame(self):
+        return self._node_frame
+
+    @property
+    def _dst_frame(self):
+        return self._node_frame
+
     def add_nodes(self, num, data=None):
         """Add multiple new nodes.