Change op function pointer to std::function, enable mutation (#6)

nnvm/include/nnvm/node.h

@@ -24,6 +24,13 @@ struct NodeEntry {
   std::shared_ptr<Node> node;
   /*! \brief index of output from the source. */
   uint32_t index;
+  /*!
+   * \brief version of input Variable.
+   *  This field can only be nonzero when this->node is a Variable node.
+   *  version is increased by one each time a Variable get composed to a mutation Op.
+   *  This information can be helpful to decide order of operations when sequence of mutation happens.
+   */
+  uint32_t version;
 };
 
 /*!

nnvm/include/nnvm/op.h

@@ -101,13 +101,13 @@ class Op {
    * \param attrs The attribute of the node
    * \return number of outputs.
    */
-  uint32_t (*get_num_outputs)(const NodeAttrs& attrs) = nullptr;
+  std::function<uint32_t(const NodeAttrs& attrs)> get_num_outputs = nullptr;
   /*!
    * \brief get number of inputs given information about the node.
    * \param attrs The attribute of the node
    * \return number of inputs
    */
-  uint32_t (*get_num_inputs)(const NodeAttrs& attrs) = nullptr;
+  std::function<uint32_t(const NodeAttrs& attrs)> get_num_inputs = nullptr;
   /*!
    * \brief Attribute parser to parse the NodeAttrs information.
    *
@@ -140,8 +140,7 @@ class Op {
    *  }
    * \endcode
    */
-  void (*attr_parser)(NodeAttrs* attrs) = nullptr;
-
+  std::function<void(NodeAttrs* attrs)> attr_parser = nullptr;
   // function fields.
   /*!
    * \brief setter function during registration
@@ -161,7 +160,7 @@ class Op {
    * \param fn The function to be set.
    * \return reference to self.
    */
-  inline Op& set_num_inputs(uint32_t (*fn)(const NodeAttrs& attr));  // NOLINT(*)
+  inline Op& set_num_inputs(std::function<uint32_t (const NodeAttrs& attr)> fn);  // NOLINT(*)
   /*!
    * \brief Set the num_outputs
    * \param n The number of outputs to be set.
@@ -173,13 +172,13 @@ class Op {
    * \param fn The function to be set.
    * \return reference to self.
    */
-  inline Op& set_num_outputs(uint32_t (*fn)(const NodeAttrs& attr));  // NOLINT(*)
+  inline Op& set_num_outputs(std::function<uint32_t (const NodeAttrs& attr)> fn);  // NOLINT(*)
   /*!
    * \brief Set the attr_parser function.
    * \param fn The number of outputs to be set.
    * \return reference to self.
    */
-  inline Op& set_attr_parser(void (*fn)(NodeAttrs* attrs));  // NOLINT(*)
+  inline Op& set_attr_parser(std::function<void (NodeAttrs* attrs)> fn);  // NOLINT(*)
   /*!
    * \brief Register additional attributes to operator.
    * \param attr_name The name of the attribute.
@@ -342,7 +341,7 @@ inline Op& Op::set_num_inputs(uint32_t n) {  // NOLINT(*)
   return *this;
 }
 
-inline Op& Op::set_num_inputs(uint32_t (*fn)(const NodeAttrs& attr)) {  // NOLINT(*)
+inline Op& Op::set_num_inputs(std::function<uint32_t (const NodeAttrs& attr)> fn) {  // NOLINT(*)
   this->get_num_inputs = fn;
   return *this;
 }
@@ -352,12 +351,12 @@ inline Op& Op::set_num_outputs(uint32_t n) {  // NOLINT(*)
   return *this;
 }
 
-inline Op& Op::set_num_outputs(uint32_t (*fn)(const NodeAttrs& attr)) {  // NOLINT(*)
+inline Op& Op::set_num_outputs(std::function<uint32_t (const NodeAttrs& attr)> fn) {  // NOLINT(*)
   this->get_num_outputs = fn;
   return *this;
 }
 
-inline Op& Op::set_attr_parser(void (*fn)(NodeAttrs* attrs)) {  // NOLINT(*)
+inline Op& Op::set_attr_parser(std::function<void (NodeAttrs* attrs)> fn) {  // NOLINT(*)
   this->attr_parser = fn;
   return *this;
 }

nnvm/include/nnvm/op_attr_types.h

@@ -12,8 +12,8 @@
 
 namespace nnvm {
 
-// These types are optional attributes in each op
-// Some of them are needed for certain pass.
+// These types are optional attributes in each operator.
+// Each attribute can be required by some passes.
 
 /*!
  * \brief Return list of input arguments names of each operator.
@@ -37,6 +37,16 @@ using FListInputNames = std::function<std::vector<std::string> (const NodeAttrs&
  */
 using FListOutputNames = std::function<std::vector<std::string> (const NodeAttrs& attrs)>;
 
+/*!
+ * \brief Check whether operator will mutate k-th input.
+ * \param index The input index
+ * \return Whether this operator will mutate index-th input.
+ *
+ * \note Register under "FMutateInput", default return false
+ * FMutateInputs enables mutation order handling correctly.
+ */
+using FMutateInput = std::function<bool (const NodeAttrs& attrs, uint32_t index)>;
+
 }  // namespace nnvm
 
 #endif  // NNVM_OP_ATTR_TYPES_H_

nnvm/src/core/symbolic.cc

@@ -13,6 +13,43 @@ namespace symbol_constants {
 const char *kNamespaceSeparator = "_";
 }  // namespace symbol_constants
 
+// auxililary version attribute in variable.
+struct VariableParam {
+  uint32_t version{0};
+};
+
+std::shared_ptr<Node> CreateVariableNode(const std::string& name) {
+  std::shared_ptr<Node> n = Node::Create();
+  n->op = nullptr;
+  n->attrs.name = name;
+  n->attrs.parsed = VariableParam();
+  return n;
+}
+
+// scan over a node's input, update the version to latest
+// If the node's op mutates a certain input variable,
+// The version of that varaible will increase
+// version is used to implicitly order the mutation sequences
+inline void UpdateNodeVersion(Node *n) {
+  static auto& fmutate_inputs = Op::GetAttr<FMutateInput>("FMutateInput");
+  for (NodeEntry& e : n->inputs) {
+    if (e.node->is_variable()) {
+      e.version = nnvm::get<VariableParam>(e.node->attrs.parsed).version;
+    }
+  }
+  if (fmutate_inputs.count(n->op) != 0) {
+    FMutateInput fmutate = fmutate_inputs[n->op];
+    for (uint32_t i = 0; i < n->inputs.size(); ++i) {
+      if (fmutate(n->attrs, i)) {
+        NodeEntry& e = n->inputs[i];
+        CHECK(e.node->is_variable())
+            << "Mutation target can only be Variable";
+        // increase the version of the variable.
+        ++nnvm::get<VariableParam>(e.node->attrs.parsed).version;
+      }
+    }
+  }
+}
 
 inline std::string DefaultVarName(const std::string &op_name,
                                   const std::string &arg_name) {
@@ -67,13 +104,13 @@ Symbol Symbol::Copy() const {
   for (const auto &kv : old_new) {
     for (const NodeEntry& e : kv.first->inputs) {
       Node *ptr = e.node.get();
-      kv.second->inputs.emplace_back(NodeEntry{old_new[ptr], e.index});
+      kv.second->inputs.emplace_back(NodeEntry{old_new[ptr], e.index, e.version});
     }
   }
   // set the head
   Symbol ret;
   for (const NodeEntry &e : outputs) {
-    ret.outputs.emplace_back(NodeEntry{old_new[e.node.get()], e.index});
+    ret.outputs.emplace_back(NodeEntry{old_new[e.node.get()], e.index, e.version});
   }
   return ret;
 }
@@ -95,8 +132,14 @@ void Symbol::Print(std::ostream &os) const {
           os << "Name: " << node->attrs.name << " Op:" << node->op->name << '\n'
              << "Inputs:\n";
           for (size_t i = 0; i < node->inputs.size(); ++i) {
-            os << "\targ[" << i << "]=" << node->inputs[i].node->attrs.name
-               << '(' << node->inputs[i].index << ")\n";
+            const NodeEntry& e = node->inputs[i];
+            os << "\targ[" << i << "]=" << e.node->attrs.name
+               << '(' << e.index << ")";
+            if (e.node->is_variable()) {
+              os << " version=" << e.version << '\n';
+            } else {
+              os << '\n';
+            }
           }
           os << "Attrs:\n";
           for (auto &kv : node->attrs.dict) {
@@ -163,6 +206,8 @@ std::vector<std::string> Symbol::ListOutputs() const {
 void Symbol::Compose(const std::vector<Symbol>& args,
                      const std::unordered_map<std::string, Symbol>& kwargs,
                      const std::string& name) {
+  static auto& flist_inputs = Op::GetAttr<FListInputNames>("FListInputNames");
+
   CHECK_EQ(outputs.size(), 1)
       << "Only composition of value function is supported currently";
   CHECK(!outputs[0].node->is_variable()) << "Variable cannot be composed";
@@ -193,7 +238,6 @@ void Symbol::Compose(const std::vector<Symbol>& args,
       }
       // switch to keyword argument matching
       if (args.size() != n_req) {
-        static auto& flist_inputs = Op::GetAttr<FListInputNames>("FListInputNames");
         FListInputNames fn = flist_inputs.get(n->op, nullptr);
         auto arg_names = (fn == nullptr) ? std::vector<std::string>{"data"} : fn(n->attrs);
         if (arg_names.size() != n_req) {
@@ -206,8 +250,8 @@ void Symbol::Compose(const std::vector<Symbol>& args,
             n->inputs[i] = it->second.outputs[0];
             ++nmatched;
           } else {
-            n->inputs[i] = NodeEntry{Node::Create(), 0};
-            n->inputs[i].node->attrs.name = DefaultVarName(name, arg_names[i]);
+            n->inputs[i] = NodeEntry{
+              CreateVariableNode(DefaultVarName(name, arg_names[i])), 0, 0};
           }
         }
 
@@ -226,6 +270,7 @@ void Symbol::Compose(const std::vector<Symbol>& args,
         n->inputs.push_back(s.outputs[0]);
       }
     }
+    UpdateNodeVersion(n);
   } else {
     // general composition
     CHECK_EQ(args.size(), 0)
@@ -253,25 +298,32 @@ void Symbol::Compose(const std::vector<Symbol>& args,
     DFSVisit(this->outputs, find_replace_map);
 
     if (nmatched == kwargs.size() && arg_counter < args.size()) {
+      std::vector<Node*> update_nodes;
       std::vector<std::pair<NodeEntry*, const NodeEntry*> > replace_plan;
-      auto find_replace_plan = [&replace_map, &replace_plan]
+      auto find_replace_plan = [&replace_map, &replace_plan, &update_nodes]
           (const std::shared_ptr<Node> &node) {
         // visit all the childs, find possible replacement
+        bool repl = false;
         for (size_t i = 0; i < node->inputs.size(); ++i) {
           NodeEntry *e = &(node->inputs[i]);
           if (e->node->is_variable()) {
             auto iter = replace_map.find(e->node.get());
             if (iter != replace_map.end()) {
               replace_plan.push_back(std::make_pair(e, iter->second));
+              repl = true;
             }
           }
         }
+        if (repl) update_nodes.push_back(node.get());
       };
       DFSVisit(this->outputs, find_replace_plan);
 
       for (const auto& kv : replace_plan) {
         *(kv.first) = *(kv.second);
       }
+      for (Node* n : update_nodes) {
+        UpdateNodeVersion(n);
+      }
     } else {
       std::vector<std::string> keys = GetKeys(kwargs);
       std::vector<std::string> arg_names = ListArguments();
@@ -303,9 +355,15 @@ Symbol Symbol::GetInternals() const {
   Symbol ret;
   DFSVisit(this->outputs, [&ret](const std::shared_ptr<Node>& node) {
       Node* n = node.get();
+      if (n->is_variable()) {
+        // grab version from variable.
+        VariableParam& param = nnvm::get<VariableParam>(n->attrs.parsed);
+        ret.outputs.emplace_back(NodeEntry{node, 0, param.version});
+      } else {
         uint32_t nout = n->num_outputs();
         for (uint32_t i = 0; i < nout; ++i) {
-        ret.outputs.emplace_back(NodeEntry{node, i});
+          ret.outputs.emplace_back(NodeEntry{node, i, 0});
+        }
       }
     });
   return ret;
@@ -325,7 +383,7 @@ void Symbol::SetAttrs(const std::vector<std::pair<std::string, std::string> >& a
     }
   }
   if (node->op != nullptr && node->op->attr_parser != nullptr) {
-    (*node->op->attr_parser)(&(node->attrs));
+    node->op->attr_parser(&(node->attrs));
   }
 }
 
@@ -366,9 +424,9 @@ Symbol Symbol::CreateFunctor(const Op* op,
   n->op = op;
   n->attrs.dict = std::move(attrs);
   if (n->op->attr_parser != nullptr) {
-    (*n->op->attr_parser)(&(n->attrs));
+    n->op->attr_parser(&(n->attrs));
   }
-  s.outputs.emplace_back(NodeEntry{std::move(n), 0});
+  s.outputs.emplace_back(NodeEntry{std::move(n), 0, 0});
   return s;
 }
 
@@ -382,10 +440,7 @@ Symbol Symbol::CreateGroup(const std::vector<Symbol> &symbols) {
 
 Symbol Symbol::CreateVariable(const std::string& name) {
   Symbol s;
-  std::shared_ptr<Node> n = Node::Create();
-  n->op = nullptr;
-  n->attrs.name = name;
-  s.outputs.emplace_back(NodeEntry{std::move(n), 0});
+  s.outputs.emplace_back(NodeEntry{CreateVariableNode(name), 0, 0});
   return s;
 }
 

nnvm/src/example/operator.cc

@@ -6,6 +6,7 @@
 #include <utility>
 
 using nnvm::FListInputNames;
+using nnvm::FMutateInput;
 using nnvm::NodeAttrs;
 
 NNVM_REGISTER_OP(add)
@@ -29,3 +30,10 @@ NNVM_REGISTER_OP(conv2d)
 
 NNVM_REGISTER_OP(add)
 .attr<std::string>("nick_name", "plus");
+
+NNVM_REGISTER_OP(assign)
+.set_num_inputs(2)
+.set_num_outputs(1)
+.attr<FMutateInput>("FMutateInput", [](const NodeAttrs& attrs, uint32_t index) {
+    return index == 0;
+  });

nnvm/tests/python/test_symbol.py

@@ -24,6 +24,20 @@ def test_default_input():
     except NNVMError:
         pass
 
+def test_mutate_input():
+    x = sym.Variable('x')
+    y = sym.conv2d(data=x, name='conv')
+    z = sym.assign(x, y)
+    t = sym.add(z, x)
+
+    try:
+        z = sym.assign(z, z)
+        assert False
+    except NNVMError:
+        pass
+
+
 if __name__ == "__main__":
     test_default_input()
     test_compose()
+    test_mutate_input()