WIP: graph interface

include/dgl/graph.h

+// DGL Graph interface
+#ifndef DGL_DGLGRAPH_H_
+#define DGL_DGLGRAPH_H_
+
+#include <vector>
+#include <stdint.h>
+#include "runtime/ndarray.h"
+
+namespace dgl {
+
+typedef uint64_t dgl_id_t;
+typedef tvm::runtime::NDArray DGLIdArray;
+typedef tvm::runtime::NDArray DegreeArray;
+
+/*!
+ * \brief Base dgl graph class.
+ * DGLGraph is a directed graph.
+ */
+class DGLGraph {
+ public:
+  void AddVertices(uint64_t num_vertices);
+
+  void AddEdge(dgl_id_t src, dgl_id_t dst);
+
+  void AddEdges(DGLIdArray src_ids, DGLIdArray dst_ids);
+
+  void Clear();
+
+  uint64_t NumVertices() const;
+
+  uint64_t NumEdges() const;
+
+  bool HasVertex(dgl_id_t vid) const;
+
+  tvm::runtime::NDArray HasVertices(DGLIdArray vids) const;
+
+  bool HasEdge(dgl_id_t src, dgl_id_t dst) const;
+
+  tvm::runtime::NDArray HasEdges(DGLIdArray src_ids, DGLIdArray dst_ids) const;
+
+  DGLIdArray Predecessors(dgl_id_t vid) const;
+
+  DGLIdArray Successors(dgl_id_t vid) const;
+
+  dgl_id_t GetEdgeId(dgl_id_t src, dgl_id_t dst) const;
+
+  DGLIdArray GetEdgeIds(DGLIdArray src, DGLIdArray dst) const;
+
+  std::pair<DGLIdArray, DGLIdArray> GetInEdge(dgl_id_t vid) const;
+
+  std::pair<DGLIdArray, DGLIdArray> GetInEdges(DGLIdArray vids) const;
+  
+  std::pair<DGLIdArray, DGLIdArray> GetOutEdge(dgl_id_t vid) const;
+
+  std::pair<DGLIdArray, DGLIdArray> GetOutEdges(DGLIdArray vids) const;
+
+  uint64_t InDegree(dgl_id_t vid) const;
+
+  DegreeArray InDegrees(DGLIdArray vids) const;
+
+  uint64_t OutDegree(dgl_id_t vid) const;
+
+  DegreeArray OutDegrees(DGLIdArray vids) const;
+
+  DGLGraph Subgraph(DGLIdArray vids) const;
+
+  DGLGraph EdgeSubgraph(DGLIdArray src, DGLIdArray dst) const;
+
+  DGLGraph Reverse() const;
+};
+
+}  // namespace dgl
+
+#endif  // DGL_DGLGRAPH_H_

include/dgl/runtime/packed_func.h

@@ -18,13 +18,6 @@
 #include "module.h"
 #include "ndarray.h"
 
-namespace HalideIR {
-// Forward declare type for extensions
-// The header works fine without depending on this.
-struct Type;
-struct Expr;
-}
-
 // Whether use TVM runtime in header only mode.
 #ifndef TVM_RUNTIME_HEADER_ONLY
 #define TVM_RUNTIME_HEADER_ONLY 0
@@ -538,8 +531,6 @@ class TVMArgValue : public TVMPODValue_ {
            typename = typename std::enable_if<
              std::is_class<TNodeRef>::value>::type>
   inline bool IsNodeType() const;
-  inline operator HalideIR::Type() const;
-  inline operator HalideIR::Expr() const;
   // get internal node ptr, if it is node
   inline std::shared_ptr<Node>& node_sptr();
 };
@@ -733,9 +724,6 @@ class TVMRetValue : public TVMPODValue_ {
   inline TNodeRef AsNodeRef() const;
   inline TVMRetValue& operator=(const NodeRef& other);
   inline TVMRetValue& operator=(const std::shared_ptr<Node>& other);
-  // type related
-  inline operator HalideIR::Type() const;
-  inline TVMRetValue& operator=(const HalideIR::Type& other);
 
  private:
   template<typename T>
@@ -1045,7 +1033,6 @@ class TVMArgsSetter {
   inline void operator()(size_t i, const T& value) const;
   // NodeRef related extenstions: in tvm/packed_func_ext.h
   inline void operator()(size_t i, const NodeRef& other) const;  // NOLINT(*)
-  inline void operator()(size_t i, const HalideIR::Type& t) const;
 
  private:
   /*! \brief The values fields */

src/runtime/c_runtime_api.cc

 /*!
  *  Copyright (c) 2016 by Contributors
  * \file c_runtime_api.cc
- * \brief Device specific implementations
+ * \brief Runtime API implementation
  */
 #include <dmlc/thread_local.h>
 #include <dgl/runtime/c_runtime_api.h>