static graph

include/mxnet/static_graph.h

@@ -0,0 +1,45 @@
+/*!
+ *  Copyright (c) 2015 by Contributors
+ * \file static_graph.h
+ * \brief the static graph of symbols
+ */
+#ifndef MXNET_STATIC_GRAPH_H_
+#define MXNET_STATIC_GRAPH_H_
+
+#include <vector>
+#include <unordered_map>
+#include <string>
+#include <memory>
+#include "./atomic_symbol.h"
+namespace mxnet {
+
+  struct StaticGraph {
+    struct StaticNode {
+      /*! \brief wrapped atomic symbol */
+      AtomicSymbol* sym_;
+      /*! \brief name of the node */
+      std::string name_;
+    };
+    std::unordered_map<std::string, int> name_id_map;
+    std::vector<StaticNode> nodes;
+    std::vector<std::vector<int> > output_index;
+    std::vector<std::vector<int> > connected_graph;
+    int FindNodeByName(const std::string& name, const AtomicSymbol* sym) {
+      int id = 0;
+      if (name_id_map.find(name) == name_id_map.end()) {
+        name_id_map[name] = name_id_map.size();
+        StaticNode static_node;
+        static_node.sym_ = sym->Copy();
+        static_node.name_ = name;
+        nodes.push_back(static_node);
+        output_index.push_back(std::vector<int>());
+        connected_graph.push_back(std::vector<int>());
+        id = name_id_map.size();
+      } else {
+        id = name_id_map[name]; 
+      }
+      return id;
+    }
+  };
+}
+#endif

include/mxnet/symbol.h

@@ -16,8 +16,10 @@
 #include "./base.h"
 #include "./tensor_blob.h"
 #include "./operator.h"
+#include "./static_graph.h"
 
 namespace mxnet {
+class CompositeOperator;
 /*!
  * \brief Symbol is the wrapper of AtomicSymbol, the reason for this indirection is that Symbol
  *  should support expressions and often passed by value. While AtomicSymbol have many subclasses,
@@ -27,7 +29,7 @@ namespace mxnet {
  *  A atomic symbol can be seen as a special case of the composite symbol with only the head node.
  */
 class Symbol {
- protected:
+ public:
   /*!
    * \brief Node is the container of AtomicSymbol, it also stores the connection of the AtomicSymbol
    *  with input symbols.
@@ -46,12 +48,19 @@ class Symbol {
     /*!
      * \brief constructor
      */
-    explicit Node(AtomicSymbol* sym = nullptr, const std::string& name = "");
+    explicit Node(AtomicSymbol* sym = nullptr, const std::string& name = "") :
+      sym_(sym), name_(name) {
+    }
     /*!
      * \brief destructor
      */
-    ~Node();
+    ~Node() {
+      if (sym_) {
+        delete sym_;
+      }
+    }
   };
+ protected:
   /*! \brief the head node of the Symbol, it could be shared in many graphs */
   std::shared_ptr<Node> head_;
   /*! \brief if the head has multiple return values, index is used to specify */
@@ -60,7 +69,13 @@ class Symbol {
   std::shared_ptr<std::vector<std::pair<Node*, int> > > arg_users_;
   /*! \brief find arg users */
   void FindArgUsers();
-
+  /**
+   * @brief Recursively parse the symbol to equivalent static graph.
+   * 
+   * @param node The current node in dfs
+   * @param graph The static graph
+   */
+  void Dfs(const std::shared_ptr<Node> node, StaticGraph& graph);
  public:
   /*!
    * \brief declare virtual destructor in case it is subclassed.
@@ -71,7 +86,14 @@ class Symbol {
    *  \param ctx context of the operator
    *  \return returns the pointer to a created operator. It is on the user to delete.
    */
-  virtual Operator* Bind(Context ctx) const { return nullptr; }
+  virtual CompositeOperator* Bind(Context ctx) const { return nullptr; }
+  /**
+   * @brief Bind the symbol to a composite operator
+   * 
+   * @param in A map denotes name and corresponding NArray for binding
+   * @return The composite operator
+   */
+  virtual CompositeOperator* Bind(Context ctx, const std::unordered_map<std::string, NArray>& in);
   /*!
    * \brief copy the symbol
    * \return a deep copy of the graph
@@ -98,6 +120,11 @@ class Symbol {
    * \return the arguments list of this symbol, they can be either named or unnamed (empty string).
    */
   virtual std::vector<std::string> ListArgs();
+  /**
+   * @brief Convert current symbol to its equivalent static graph representation.
+   * @return the static graph
+   */
+  virtual StaticGraph ToStaticGraph();
   /*!
    * \brief create Symbol by wrapping AtomicSymbol
    */

src/symbol/symbol.cc

@@ -6,20 +6,11 @@
 #include <dmlc/logging.h>
 #include <mxnet/symbol.h>
 #include <mxnet/registry.h>
+#include <mxnet/static_graph.h>
 #include <iterator>
 
 namespace mxnet {
 
-Symbol::Node::Node(AtomicSymbol* sym, const std::string& name)
-    : sym_(sym), name_(name) {
-}
-
-Symbol::Node::~Node() {
-  if (sym_) {
-    delete sym_;
-  }
-}
-
 void Symbol::FindArgUsers() {
   arg_users_.reset(new std::vector<std::pair<Node*, int> >);
   // depth first traversing
@@ -144,14 +135,14 @@ Symbol Symbol::Create(AtomicSymbol *atomic_symbol)  {
   std::vector<std::string> args = atomic_symbol->DescribeArguments();
   std::vector<std::string> rets = atomic_symbol->DescribeReturns();
   // set head_
-  s.head_ = std::make_shared<Symbol::Node>(atomic_symbol, "");
+  s.head_ = std::make_shared<Node>(atomic_symbol, "");
   // set index_
   s.index_ = rets.size() > 1 ? -1 : 0;
   // set head_->in_index_
   s.head_->in_index_ = std::vector<int>(args.size(), 0);
   // set head_->in_symbol_
   for (auto name : args) {
-    s.head_->in_symbol_.push_back(std::make_shared<Symbol::Node>(nullptr, name));
+    s.head_->in_symbol_.push_back(std::make_shared<Node>(nullptr, name));
   }
   // set head_->out_shape_
   s.head_->out_shape_ = std::vector<TShape>(rets.size());
@@ -169,4 +160,29 @@ Symbol Symbol::Create(const std::string& type_name,
   return Create(atomic_symbol);
 }
 
+StaticGraph Symbol::ToStaticGraph() {
+  StaticGraph graph;
+  Dfs(this->head_, graph);
+  return graph;
+}
+
+CompositeOperator* Symbol::Bind(Context ctx, const std::unordered_map<std::string, NArray>& in) {
+  StaticGraph graph = this->ToStaticGraph();
+  return NULL;
+  //TODO: pass the graph and in to initlialize a composite op.
+}
+
+void Symbol::Dfs(const std::shared_ptr<Node> node, StaticGraph& graph) {
+  int id = graph.FindNodeByName(node->name_, node->sym_);
+  for (size_t i = 0; i < node->in_symbol_.size(); ++i) {
+    std::shared_ptr<Node> parent = node->in_symbol_[i];
+    int parent_id = graph.FindNodeByName(parent->name_, parent->sym_);
+    graph.connected_graph[parent_id].push_back(id);
+    graph.output_index[parent_id].push_back(node->in_index_[i]);
+    if (parent->sym_) {
+      Dfs(parent, graph);
+    }
+  }
+}
+
 }  // namespace mxnet